Transcript for:
AQA GCSE Biology Paper One Summary

everyone and welcome to miss estri biology and to this enormous video covering everything that you need to know for AQA GCC biology paper one I hope your comfy and you've got a drink ready because it is pretty long so you might want to watch it at times too speed to get through it really quickly especially if you're here watching the night before the exam if you are shout out to all you crammers best of luck tomorrow now if you do want even more help boosting your grade then don't forget you can check out my GCC notes these notes cover all of the theory for GCSE biology including key terms topic summaries examiners tips from actal examiners and also you've got questions and answers at the end of every topic so I'll link these below but for now enjoy the video and best of luck for your gcsc exams first of all we've got here our two examples of eukariotic cells for gcsc we have a plant cell and an animal cell and if you haven't already seen my video on eukaryotic cells compared to procaryotic cells I'll link up here so you can go and take a look so some of the key structures inside a UK carotic cell are they have cytoplasm they have a cell membrane and they have genetic material that is within a nucleus rather than loose in the cytoplasm now we're going to go into more detail on the different structures and what their functions are though in the animal cells and the plant cells so let's start with an animal cell so we said they have cytoplasm cell membrane but they also have mitochondria they have a nucleus which we said contains the genetic information and they have ribosomes and we're going to go through the function of these a little bit later in the video now if we compare this to a plant cell they do have lots of structures in common so they also have cytoplasm they have a cell membrane they have mitochondria now notice here I've called it mitochondrian that's because it's only pointing to one and the singular is mitochondrian the plural is mitochondria they have a cell wall they have a permanent vacu which is filled with sap a liquid they have chloroplasts a nucleus which contains the genetic information and ribosomes now out of all of those structures inside of a plant cell it's actually only these three which you only find in a plant cell and that is quite a common question for this topic at gcsc it's either being able to label the structures in an animal or a plant cell um or it could be suggesting structures that you find in a plant cell that you do not find in an animal cell and these would be your three potential marks for that question so we focus on now what the actual functions are of these different structures so we talked about cytoplasm and this is a liquid gel so it's quite a thick liquid and this is what the organells are suspended in and what we mean by organel is the different structures you find within the cell so these structures or organel are floating in this thick liquid it's also where most chemical reactions take place the cell membrane this is the layer surrounding the cells that you have in both an animal cell and a plant cell and that layer controls what can enter and exit the cell so that's what we mean by it's controlling the passage of substances the nucleus so this is where you find the genetic material and it controls the activities of the cell as well as containing the genetic material the mitochondria this is where aerobic respiration occurs and that means that most of the energy from a cell is released from the mitochondria ribosomes this is where protein synthesis occurs so that is where all the proteins for the cell are made chloroplast which you only find in Plants the reason they're green is because they contain a pigment which is a protein which has a color they contain this pigment called chlorophyll and chlorophyll absorbs the energy from light and that energy is used in photosynthesis so chloroplasts function is for photosynthesis which is how plants make their food the cell wool which you only find in the plant cells not the animal cells contains a molecule called cellulose and that molecule makes the cell wall really really strong so it gives the cell support and it's that cellulose cell wo which is really strong which stops the plant cells from bursting if they do swell up with lots of water the permanent vacuum so this is filled with cell sap so that is a liquid and that liquid again it helps to support the cell and make it really rigid so you have that liquid in the center pushing outwards to make the cell really rigid I'm going to be going through procaryotic and eukariotic cells in this video for gcsc biology so let's have a look then at some of the key differences between procaryotic and eukariotic cells now first of all just to let you know this is just a way to group cells based on similarities or differences in their structures so eukaryotic cells this is plant and animal cells and you'll be familiar with that from keystage three whereas procaryotic cells that would be bacteria cells some of the key structures that you have in animal and plant cells which are our eukariotic cells are the cell membranes they have cytoplasm and this is the key one here their genetic material so the DNA is found in the nucleus and if we compare this to a procaryotic cell like bacteria first of all they are much much smaller in size so bacteria cells are much smaller than plant and animal cells but also there are some differences there are some similarities though also so they do both have cytoplasm they both have cell membranes now only plant cells have a cell wall whereas all the procaryotic cells will have a cell wall the big difference is procaryotic cells do not have a nucleus they do still have genetic material which sometimes is DNA but you will just find that as a single Loop loose within the cytoplasm they also sometimes have an extra circular Loop of DNA which is called a plasmid so if you were asked in an exam question to identify similarities between eukaryotic and procaryotic cells the best two to go for would be cell membranes and cytoplasm because that is consistent across plants animals and bacterial cells if you were asked in an exam question to point out a difference between these two types of cells the best option would be for saying would be to say that eukaryotic cells have a nucleus that contains genetic material whereas procaryotic cells do not have a nucleus and their genetic material is just a single Loop which you find in the cytoplasm so if we have a look then at these two different types of cell cells and we said eukariotic cells are plant cells and animal cells so the cytoplasm is the liquid part that we can see here the cell membrane is the layer which controls the passage of substances into and out of a cell and then inside of the nucleus that is where you find the genetic material now you'll notice that there are other structures here so mitochondria and ribosomes but I go into detail on that in another video and I'll link that up here so if you do want to see that GCC video looking at plant and animal cells in more detail go and take a look so procaryotic cells we said bacterial cells now they do still have cytoplasm which is the site of most chemical reactions they have a cell membrane which is the layer that controls what can enter and exit the cell they also have a cell wall to provide some structural support and here is their genetic material which we said is a single Loop now it looks a bit more complicated than that just because it's a very big loop which is quite tangled up but the key thing is it's not found inside of a nucleus some bacteria also have a plasmid which is this circular Loop of DNA now you do not always find plasmids so that's only sometimes in bacteria and you might notice these tail likee structures these are fella and those are again only sometimes found and there to help the bacteria to swim and move around so because it's only sometimes found you wouldn't get a mark for necessarily saying that you would get marks for pointing out the key structures which are always present which is cytoplasm cell membrane cell wall and genetic material in a single Loop but not inside of a nucleus now I said that bacteria cells or Pro carotic cells are much much smaller so let's have a look at this scale to put that into context so here is the UK carotic cell and that can range between 100 micromet to 10 micromet so some cells are much bigger so for example a human egg cell is a much larger cell prootic cells are around 1 micrometer so they can be around 100 times smaller in size so is a big difference now other things just to point out on this scale you will learn within the gcsc about different microscopes a light microscope and an electron microscope and this is just showing you compared to what you can see with your human eye so as in with no assisted help just with your eye compared to what you could see using a light microscope and those are the microscopes you typically have in school an electron microscope is much much more powerful has a higher magnification and a higher resolution and they're much more expensive so you would not have one of these in school but because they have higher resolution and magnification you're able to see much much smaller objects um and they're still clear in this video we're going to be covering a GCSE topic on Cell specialization now in this lesson what I'm going to be covering is what we mean by a sell to tissue organ and organ systems and then the whole organism the reason for that is you need to know what all of those structures mean before we then look at the next part and that is how different cells are specialized for their function and the list of cells we're going to go through are those that are required for AQA biology so first of all then let's have a look at what we mean by these different levels of organization and this comes up later in the gcsc and what we mean by organization is how all the different parts of a body or it could be a plant are organized so cells are the basic building blocks of all living organisms then the next largest thing is a tissue and that's a group of cells with a similar structure and function tissues then will all work together to make an organ so organs are aggregations or groups of tissues performing a specific specific function organs are then organized into organ systems so we can see in this diagram the circulatory system which is made up of the heart and then arteries veins capillaries and lastly the entire organism is made up of lots of organ systems so that is what we mean by organization now if we go on to the different specialized cells you need to know so we're going to start with the animal cells and firstly a sperm cell now for all the specialized cells you need to know what the function is and how the structure of the cell links to that so the function of the sperm cell is to swim to reach the egg carry the genetic material and fertilize that egg so the structures that are in place are first of all we can see this long tail and that will whip back and forth so that it can swim and move towards the Exel in this bit of the sperm so in the middle section there's lots and lots of mitochondri Andria and that is so that energy can be released and that energy is then used for the tail to move the acrosome is this little part right at the top of the head and that contains digestive enzymes so when the sperm does reach the egg those digestive enzymes are released and it breaks down the outer layer so the sperm's nucleus can then combine with the egg cells lastly it does have a large nucleus and that's because it contains half the genetic material that is required to make the new Offspring so next cell is a muscle cell the function of this is for Contracting and relaxing so in the skeleton or around the skeleton it's so that those bones can move you do also have muscles lining in certain organs so for example the stomach will have stomach muscles which contract and relax to help turn up food so the structure there are muscle fibers that are made up of two different proteins and those proteins slide over each other and as they slide together that makes the muscle contract and as they slide back apart that makes the muscle relax now to be able to do that energy is required so there are lots of stores of glycogen and that is lots of glucose molecules bonded and stored away so that means that when respiration is required to release energy for the muscles to contract that glycogen store can be broken down to release the glucose needed for respiration now lastly aerobic respiration happens in the mitochondria so you also find lots of mitochondria in the muscle cells last animal cell is the nerve cell so the function of nerve cells or neurons is to carry electrical impulses around the body really really quickly so that you can respond to your surroundings the structures then are first of all we have lots of these dendrites and these are the branching parts coming off the nerve cell and there's lots of them so that they can make connections with lots of other nerve cells so the impulse or this message can be passed around the body rapidly the axon is this long thin wire section and it's a bit like an electrical wire it carries the electrical impulse you then will have gaps between the end ings of the nerve and between another nerve and we call those gaps synapses and at that point you will have the message being sent as a chemical impulse or message so then if we go on to the plant cells first of all we're going to be looking at this group of plant cells that makes up the xylm tissue so the whole xylm is a tissue because it's made up of lots and lots of cells working together but if we think about the structure of those and the function we can see on the diagram the function is to carry water around the plant and there will be dissolved mineral ions within that water so it transports water and mineral ions from The Roots where it's absorbed to the rest of the plants it has ligin in the cell walls which makes it really strong so that it doesn't fall down or um break under the high pressure of water moving through it we you can see as well that it forms this hollow tube a bit like a hose pipe so that water can move through it really easily so the inside of those xylm cells is actually dead and that's why it's empty so flum cells we can see that next to the xylm the function of these Flo cells is to transport sugars that have been made in the leaf in photosynthesis around the plant the structures then hopefully you can see here there this perforated which just means there's lots of holes in it this perforated cell wall and we call it a c plate because it's a bit like a syn it's got lots of holes in and that will allow the sugar solution to transport around the plant now it's also pretty hollow inside so it is like almost like a hose pipe apart from these C tube elements and that means they have companion cells so we've got these cells that align the FL which we call Companion cells because they help the flm cell so they will have mitochondria in to provide the energy that the flam cells need because the flam cell itself doesn't have mitochondria within it so the last one is the root hair cell the root hair cells are responsible for absorbing water and mineral ions from the soil water by osmosis mineral ions by active transport the adaptations then are first of all this shape it's called a root hair cell because of that protruding structure that looks a bit like a hair and that provides a large surface area for active transport and osmosis there is this large permanent vacu as well and that helps to increase the speed of water uptake by osmosis lastly it contains lots of mitochondria and that is to provide energy for active transport to uptake those mineral ions in this dcsc biology video we're going to go through cell differentiation so what we're going to go through today is what we mean by cell differentiation why it's important how cells differentiate and just looking at the purpose of that process so cell differentiation what that means is that all animals and plants are unspecialized in the very early stages of development so if you think about a human in the very early stages when they're just a ball of cells or an embryo that ball of cells is called stem cells or it contains stem cells and those are cells that don't have any adaptations yet so they're not specialized now when they do become specialized we call that differentiation so they've become different they differentiate into lots of different types of specialized cells so we can see here we've got a nerve cell red blood cells and other cells so that is what we mean by cell differentiation to cell differentiation in animals this happens very very early in the development for animals and that's what we're seeing here we've got just the zygote initially so that is the cell that forms after a sperm and egg cell fuse then after a few few days we get the cells dividing until you just have a ball of cells which is the embryo by the time that a human is a baby so being given birth to they already have almost all of their specialized cells and that happens by genes being switched on or off so that each specialized cell creates a specific selection of proteins within that cell now those specialized cells were mainly Dev divide by mitosis to make more of those specialized cells but by the time you are an adult and fully grown mitosis is actually no longer for growth because you're fully grown but instead mitosis is just for repairing any damaged cells or replacing damaged cells now in contrast in Plants cell differentiation happens at different times most plants can actually continue to differentiate even after early development the undifferentiated cells or the stem cells are found at these actively growing regions and we call those regions that are continuously growing marry stems stems and roots or the tips of the stem and the tips of the roots are merry stems and that means that there's constant mitosis happening at those regions for growth so so because of that you can actually take a cutting from the tip of a root or a chute plant it in soil with some plant hormones and from that tiny cutting an entire new plant would grow and that's because all of those cells were undifferentiated and therefore they could then become specialized to make a whole new plant in this video we're going to be finding out about microscopes so in this lesson we're going to be looking at how microscopy techniques have developed over time how electron microscopy has increased the understanding of the inside structures of a cell and looking at what we mean by magnification and resolution and how those differ between light and electron microscopes so you do need to know a little bit about the history of the microscope you could be asked to label the different structures in the parts of a microscope because it is one of your required practicals to know how to use a microscope scope so we've got that there on this image now light microscopes were actually first developed in the mid 17th century so they have been around for a long time and cells are very very small they're the basic building blocks that make up all organisms but most of them can only actually be seen with a microscope because they're so small microscopes continue to develop and it was in the 1930s that the electron microscope was developed now the electon microscope has a much higher magnification and resolving power compared to the light microscope and we'll go through later on what those two terms mean but what it meant for the use of microscopes is we were now able not just to see the cells but to see the inside of cells and we call that the subcellular structures so if we have a look at some of the properties of light microscopes so the way they work work is a beam of light is used to create the image they can magnify up to 2,000 times so that means whatever you're looking at can be viewed 2,000 times bigger that's the microscope that you'll be using in your school and there's two reasons why first of all they're much cheaper and they're much easier to use with the light microscope you can actually view living and non-living specimens and that's what we can see over here top diagram we have a live nematode worm and down here at the bottom this is actually a live leech that we're looking at you can also see that you can get color images with the light microscope but we can't really see the details of the cells or any individual cells and that's where the electron microscope is much much more useful now the way it creates an image is by releasing a beam of electrons now electrons have a much shorter wavelength than lights and that is why that we get this much higher magnification we can actually magnify 2 million times they are very very big and expensive and much more complicated to use you can't actually use live specimens on these microscopes the reason for that you learn at a level but essentially it's because you have to have a vacuum for this microscope to work and a vacuum is when you from removed all of the air so you couldn't have anything living in that the images that are produced are always black and white you can though artificially color that image in Photoshop for example and that's what we can see in this diagram above they've put colors onto that black and white image now there's two different types of electron microscopes there's one that's called a transmission electron microscope and that's what we can see down here at the bottom the results of you get these 2D images a scanning electron microscope gives a 3D image and that's what we can see on the top one this 3D image of eoli and cocky bacteria the lower image from the transmission electron microscope has got this image of mitochondria which are the subcellular structures now if we have a look at what these two key terms magnification and resolution actually mean magnification is how many times bigger the image looks compared to the actual size of object resolution is the ability to see two different points as separate and basically that is to do with how crisp and clear the image looks so the higher the resolving power of a microscope the more detail you can see in your image and that's why the electron microscopes you are able to see the these subcellular structures in detail because you can magnify more and you have this higher resolution so you get a clearer image so just to show you the comparison the resolving power which is linked to the resolution the resolving power of the light microscope is 200 nanom the scanning electron microscope is 10 nanometers and a transmission electron microscope is 0.2 nanometers so that means you can still see two objects as separate when they are only the distance away from each other of two atoms so that is a very very high resolving power in this video I'm going to be going through the GCS required practical for inhibition zones so keep watching to find out all about how and why to follow a septic technique how you then do the write up and what the results show now in this investigation we're going to be looking at which antibiotic or you might be using other antimicrobal to see which is the most effective at killing a particular bacteria so just a reminder that antibiotics these are medicines that can treat bacterial diseases by killing the bacteria and in our experiment we're going to be guessing what's called inhibition zones and these are the clear areas around the antibiotic disc or whatever it is that you have put down where the bacteria that you grew has been killed by that particular antibiotic and if you have no inhibition Zone that means that that antibiotic is ineffective or it does not kill that particular bacteria now whenever we grow microbes we have to make sure we are working aseptically and we follow what's called aseptic technique and this is when we work in a way that's completely sterile and clean to make sure that we don't get any contamination on the petri dish so some examples are making sure that you clean down your working surface with disinfectant before you begin but also at the end to make sure you don't then transfer that bacteria to other surfaces within the school we wash our hands with soap before and after before to make sure we don't contaminate the Petra dish and after so we don't contaminate the rest of the we work near a buns and burner and that's because air will be drawn upwards as it gets hot following the convection currents and then as it goes through the bunts and Flame that will kill any microbes in the air as that air cools it will then go back down again and we'll get this circulation of air being sterilized so if you work near the buns and burner when you have to take your lid off the air around you should be being sterilized any metal equipment we sterilize by putting into the buns and burn of flame as well and when you do have to open your petri dish to put the antibiotic discs in and to put the bacteria in as well as working near the buns and burner try and only open the lid a little bit to reduce the chance of any microbes in the air landing on your plat so aseptic technique is working as we said completely sterile and this is so important because if you do get contaminations on your petri dish then the bacteria or maybe fungi that grows it might actually out competes the bacteria that you want to grow and examine so it'll be competing for the available nutrients and the AAR jelly the water available in the agar jelly um the space to grow or the new microb might actually release chemicals that kill the bacteria you're growing so let's watch the method then first of all you disinfect your work surface then we're going to light the bunson burner I've washing my hands there with an antiseptic and antibacterial gel and then labeling the Petra dish with my initials the date and eoli that's the bacteria I'm growing I also split it into three so that we can see where to place the discs now we're going to put on the bacteria and straight away we are sterilizing the syringe I've now got a sterile spreader and I'm spreading it evenly all over the plate I'm working near the buns and burner where the sterile air is next then we're using sterile forceps to put our three antimicrobials on in the three positions that we've already sectioned out on the Petry dish sterilize again just in case you've got any ecolon and then we're putting tape just on two sides so oxygen can still get in for the bacteria and then aseptic technique at the end so let's have a look at the results then unfortunately my ones here the bacteria didn't actually grow enough to be able to see these really clear inhibition zones so here was my antibiotic there was a slight inhibition Zone but you just can't really see it in this picture and there was a slight one around my antiseptic garlic though there was no inhibition Zone and in fact even more bacteria started to grow around that so we're going to use these results instead because although it's just a diagram it's useful to be able to practice the scill of the area of a circle and coming to a conclusion so let's work out then the area of the inhibition zones what you would need to do for this is use a ruler with millimeter markings on and then from the very center of your paper disc to the outer layer of your inhibition Zone you would measure to get the radius or if you're going to do the diameter instead just make sure you are going directly through the middle of your paper disc once we've recorded those we can then work out the area of the inhibition Zone it's a circle so it's pi r s and just make sure that you do record all of your results in the same column to the same number of decimal places so now we've recorded our results you could then be asked to describe explain or come to a conclusion based on your results now the description of these results is where you are just saying the patterns of what you can see so we could say descriptions like there is an inhibition Zone around a b and d but not around C we have the largest inhibition Zone around D and the smallest around B not including C which had zero that would be our description now I've actually linked the conclusion and explanations together over here so one conclusion could be that a b and d are all effective at killing this particular bacteria the explanation is because they all had inhibition zones and that indicates that they had killed bacteria another conclusion is that antibiotic c does not kill the bacteria and the reason we know that this is our explanation is because there was no inhibition Zone around it finally we could have the conclusion that D is the most effective antibiotic out of these four at killing this particular bacteria and the explanation is it had the largest inhibition Zone which means it had killed the most bacteria in this video I'm going to be going through mitosis for gcsc biology so have you ever found yourself wondering how new skin cells are made to heal a Cuts or how an embryo goes from being just a ball of cells to a fetus how your fingernails grow or how plant roots grow well if you have the answer to all of those is mitosis and that's what we're going to be going through today so one type of cell division is mitosis and it's really important for growth and development of multicellular organisms like plants and animals new cells that are grown must be identical to the original if they're going to be replacing or adding to the existing cell C and that's so that these new cells also perform exactly the same function now when we say identical we're meaning genetically identical and genetically identical means that inside of the nucleus they have exactly the same DNA so the same chromosomes with the same genes and alals on them the cell cycle is split into three key stages and within the cell cycle the DNA doubles and then the cell divides and that's how we get these two identical cells so the three stages the first one is the cell has to grow if that cell is going to split in half to make new cells then it has to grow first of all so that every cell doesn't become smaller and smaller and smaller so that's what we have as one of the main stages of the cell cycle the cell gets bigger and all of the organ which are the internal cell structures they also replicate so things like the ribosomes and the mitochondria as well as that all of the DNA doubles so DNA replication happens so there's now two copies of every single chromosome and that is so that when the cell does split in half both of the new cells have the correct number of each chromosome which in humans is 23 pairs or 46 in total the last stage is the actual cell divides so we have the cytoplasm splits and the cell membrane splits and that is how we get our two new cells so this is just showing you some of those stages this cell has already gone through the first two steps the cell growth and the DNA replication and then we can see that the cytoplasm is starting to pinch inwards and starting to split as is the cell membrane just hereit until eventually it does split and we now have two identical cells to each other and they're also identical to the original cell that they're both made from so where does mitosis occur it happens in nearly all of your body cells in fact the only body cells that it doesn't happen in are the sex cells so that would be your gametes um that is where we don't have occurring when we're making Gam Meats it does happen in particular in the root tips of dividing plants and that's what we can see here this is a root tip from a plant under the microscope and at the very tip that is where mitosis is happening so the roots can continue to grow in length and reach lots of water another example is in humans when embryos are growing so here we have the first cell that' be a zgate after a sperm and egg fuse and all of these new cells are doubling and replicating that is by mitosis now sometimes mitosis does go wrong usually mitosis happens absolutely as it should because there are controls in place to make sure that your cells are replicating only when you need new cells and at a speed that is appropriate however sometimes those controls stop working and that will then mean that a cell can divide uncontrollably by mitosis and you end up with far more cells than you actually need and that is what a tumor is it's a group of cells that have been created by this uncontrollable division now some Chums are benign which means they're not cancerous some are malignant which means they are cancerous in this video we're going to go through stem cells for GCS biology so first of all what do we mean by a stem cell these are undifferentiated cells which have the ability to continually replicate into the same type of cell but can also differentiate which means to become a specialized cell plants have stem cells and these are found in the merry stems and that's what we call the actively growing parts of the plant so for example the tips of the roots and the growing regions in the stem they can differentiate into any plant cell throughout their entire life in contrast adults we do have stem cells but we find them in limited places such as the bone marrow and these bone marrow cells which are stem cells they can differentiate into different cells but only a small number of different types of cells um which are the blood cells now in humans and other animals the most useful stem cells Are embryonic stem cells and these are found in very very young embryos so this is shortly after the sperm and egg fertilize and you just have a group of cells now those stem cells have the ability to grow and divide rapidly into any type of cell so this just summarizes the three types of stem cells we said you might want to pause and note this down I'm just going to pick out some of the potential uses and the disadvantages for plants you could use these stem cells to make clones or cuttings and this is a way of growing plants very very quickly and cheaply because instead of planting seeds and waiting for them to grow you can cut off a section of the plant and that will then grow the new cells needed such as roots to make a new plant and this is really useful as a way to prevent the extinction of rare species or being able to create special crops that you're after adult stem cells we said can only differentiate into a small number of cells for example blood cells now this can still be useful because it can be used to treat a range of blood diseases but because these stem cells can only differentiate into blood cells it is a small number of diseases that these adult stem cells can be used to treat and also the mechanism behind how you do this can involve viruses so that means you could transfer a viral infection as well and embrionic stem cells because they can differentiate into any type of cell they could be used to treat a wide range of diseases because you would then allow the stem cell to differentiate into a particular specialized cell to replace faulty ones for example you could replace cells in the pancreas to treat diabetes and you could replace damaged neurons in the spine to treat paralysis the downside though is in doing this taking the stem cells from an embryo it destroys the embryo which involves lots of ethical and religious concern you would also have to make sure that the stem cells that you're using to treat a patient are identical to the stem cells from the embryo and the only way this is possible is if you make a clone of your patient and that is what we mean by therapeutic cloning now therapeutic cloning does mean that you then let the embryo Go full term to birth and you create a mini me that's not what therapeutic cloning is it's when you just clone a patient to get an embryo which you can then use the stem cells for to treat certain diseases and the way this is done is we removed nucleus from the patient and we put that nucleus into an empty egg cell and that is the equivalent of fertilization so that clone which is now to start embryo has identical DNA to the patient the stem cells are then removed from that cloned embryo and they can then be treated with particular hormones and chemicals to so that the cells will differentiate into particular specialized cells that can then be used to treat whatever the disease is and the patient's body won't reject those cells because they're a clone of their own so this could be used to treat medical conditions like diabetes now there are pros and cons of this idea of using embryonic stem cells some of the advantages we've said you can use them to treat many diseases you can grow lots of embryos in a lab and in terms of the embryo this is a completely painless technique for the embryo the disadvantages are though although it doesn't hurt the embryo it will cause permanent harm or death of that embryo the embryo can't give consent and also it might not even work stem cells have this property of replicating rapidly so sometimes even when the stem cells are then put into the patient it can replicate so much that it forms a tumor so embryonic stem cells is not a perfect science at all and you need to be aware of the pros and the cons of potentially using stem cells in this video I'm going through diffusion for GCS biology so Fusion is a type of transport and it's how some substances cross the cell membrane into a cell or move out of the cell so have you ever thought about why is it possible if you're in your bedroom that you can smell dinner cooking or why the smell of an air freshener is all around the house well the answer is diffusion diffusion is the spreading out of particles in either a solution so in a liquid or a gas and they move from an area of high concentration to a lower concentration so we can see here we've got this High concentration of particles on one side of the membrane and they diffuse or move across the cell membrane to where there is a lower concentration and this movement happens until you reach equilibrium which means you've got the same concentration on both sides or in all locations so examples of where this happens in biology oxygen and carbon dioxide move by diffusion in gas exchange so in the Alvi oxygen diffuses from inside the alvioli into the blood capillaries and carbon dioxide diffuses from the blood capillaries back into the alvioli to be exhaled Ura which is a waste product diffuses from the cells where it's made into the blood plasma and then it's transported to the kidneys to be removed so what factors will increase the rate of diffusion there's three the difference in concentration gradients the temperature and the surface area of the membrane so the difference in concentrations is the concentration gradient and the steeper the gradient the faster diffusion will happen and it's a bit like we can see here these snowballs rolling down the hill the steeper the gradient of the Hill the faster they're going to roll down down and it's the same idea with particles moving in diffusion the higher the concentration in one area the fast those particles will diffuse to the area where there's a lower concentration secondly is temperature the higher the temperature the more kinetic energy the particles have and kinetic energy is movement energy so if those particles are moving faster then diffusion will happen faster lastly is the surface area of the membrane so this only applies to if it's diffusion across a membrane so the larger the surface that particles can diffuse across the faster it will happen because there's more space for those particles to move through this video I'm going to be going through osmosis for GC biology so let's start by looking at the definition osmosis is a type of transport but it is only the movement of water and specifically in the exam you'd need to say it's the diffusion of water now if you're not sure what diffusion is I'll link my video up here that I've already covered on diffusion the direction that the water moves is from a dilute solution to a concentrated solution and that's what I've demonstrated on this diagram here the dilute solution there are lots of water molecules compared to only two solute molecules in a concentrated solution you have much fewer water molecules compared to your solute and that could be dissolved sugar it could be dissolved salt for example and the water moves through a partially permeable membrane and that's what this dashed line is representing and your cells are partially permeable membranes or the cell membranes are and what that means is there is this surrounding layer but there's tiny holes which will selectively allow certain molecules to pass across and in this case water is able to pass through that membrane so that's our definition but you could be asked to describe the effect that osmosis has on plant material and in this example I've got potato cubes in three different solutions which are all of different concentration and we're going to look at at what would happen to the potato in each of them so in the first one we have put a potato in a concentrated solution now what that means is there is a more concentrated solution outside of the potato compared to inside and therefore the water will diffuse out of the potato into the surrounding liquid so the potato will decrease in Mass because it's losing water the next one that we have is a dilute solution and this time that would mean that if we had a really dilute solution for example if it was just pure water with nothing else dissolved in it then the water would move into the potato because inside of the potato there would be a more concentrated solution so in that instance the potato would actually gain Mass because water is entering in our third scenario we have a solution which is exactly the same concentration as the inside of the cell for whichever solute we've made it up for whether that's sugar or salts and if that's the case there won't be any overall movement or net movement of water because it's already at equilibrium or in other words there's the same concentration inside and out now one of the required practicals is linked to that but I'm not going to go through that in detail just very briefly to show you um the data skills linked to this so we've got our three solutions and we talked about which potatoes would gain Mass which would lose mass and the one where it was in the same concentrated solution then that wouldn't gain any mass at all but if we want to find that out we have to weigh the potatoes at the start put them in the solutions then we'd leave them for about 30 minutes so there time for osmosis to happen take the potatoes out and we actually have to dry the outsides because we only want to know the mass inside of the potato not any mass of the water droplets on the outside so we then tap them dry don't squeeze them but just tap them dry and reweigh them and here I have some results and what we can see here is the change in mass at the different concentrations and this is more than the ones we saw on the diagram before now if there's no change in mass that means that there wasn't any overall diffusion of water so osmosis wasn't happening and if that's the case we can find out on this graph what the exact concentration of the potato must be because where our line intercepts zero on the Y AIS which I've circled here that means means that there was no change in mass so no water was moving in or out of the potato and that must be because the solution the potato was in is exactly the same concentration as the potato itself so in this example that would mean that the potatoes concentration was 40% now we haven't got what the solution itself was but that is a really common question so you're looking at where there's zero change in mass that is what the concentration of your plot material is now it would actually be better to present that as the percentage change in mass and the reason for that is not all of the potatoes that we were measuring would have been exactly the same mass to begin with so to make sure it's a fair comparison we actually need to calculate the percentage change in mass so this table shows you all the data that was collected the initial mass of the potato before it went in the solution the final mass of each Potato Cube after it been in the solution then we've worked out the difference so what the change in mass was and whether it was an increase or negative indicates a decrease and the last column is the percentage change mass and this is the formula below for how you would calculate that so you'd need to do the change in mass divided by the initial mass and then Times by 100 and that is one of the math skills that you are expected to know so you do need to learn that formula in this video we're going to be going through active transport for GCC biology so let's start by looking at the definition of active transport it's the movement of substances from a dilute solution to a more concentrated solution or in other words it's going against the concentration gradient so if we have a look at this diagram over here the dilute solution has lots of water molecules but only two of our solute molecule and that could be sugar it could be salt whatever the solute is that has dissolved and in comparison the concentrated solution has very little water compared to the solute available so when we say it's going against the concentration gradient we mean we're going from an area where there's very little of that solute to where there is a lot and the way you use the term in the mark scheme is dilute solution to more concentrated solution now because this is going against the concentration gradient energy is needed to help move those molecules to the concentrated side so that's the definition and there are two key examples that you need to know for a QA the first one is the active transport is how plants absorb mineral ions from the soil into their root hair cells so the roots here on those roots there are root hair cells which are the cells that have that long protruding section and the soil itself doesn't actually have a very concentrated solution of these mineral ions especially compared to the concentration already within the cell but the plant still needs lots of mineral ions continuously and that's because those mineral ions are really important for the plant to be able to grow healthily and that is why active transport occurs to make sure this mineral arms are moved against the concentration gradient into the plants the second example is in animals for example in humans in our guts sugar is absorbed into the blood stream from your gut by active transport and it's a similar idea even though in your gut compared to your blood you might have a low concentration of sugar and a high concentration of sugar in your blood we still need to be able to move every last bit of sugar from your gut into the blood and that's because sugar is constantly being used for respiration in your cells and without respiration your cells wouldn't be able to survive now the final thing you could be asked linked to active transport but also diffusion and osmosis and if you haven't seen my two videos on those I'll link them at the end you could be asked to compare similarities and differences between these three so I've got this ven diagram just to demonstrate so diffusion that is how an example is how gases exchange at a leaf osmosis is only the movement of water and it's by diffusion it's across a partially permeable membrane active transport is the only one that requires energy it's the only one that demonstrates have mineral is into the repair cell and it's the only one that goes against the concentration gradient so those are all our differences some of the similarities then diffusion and osmosis are both passive meaning they do not require energy they are both also moving from a high to a low concentration with osmosis by high we mean a high concentration of water to a lower concentration of water for diffusion and active transport it involves the transport of the solute because we said osmosis is the movement of water and then all three of them are types of movement so that's the only thing that all three have in common for GCS biology first of all we're going to go through this introduction of what what's coming up in this video but I do want to point out that at the end of this video there are also 10 questions and the answers to test have you understood all of the information so don't miss those questions at the end but introduction then this topic on organization is looking at how the body is made up of complex systems and how they all work together to Keep Us Alive and healthy so you learn about the digestive system respiratory system circulatory system then also the Transport Systems in plants and there's a little bit as well about what could make these systems go wrong and things like Chron heart disease how you can overcome those so this term organization is referring to all of the different structures within an organism and how those increasingly complex structures work together to create a final organism you need to know about cells tissues organs organ systems and organisms cells was all of topic one which if you haven't watched my video on topic one I'll link it up here so cells are the smallest of the structures they're the basic building blocks of life then we get tissues which could be made up of thousands or even millions of cells and they're groups of similar cells that work together to carry out a specific function such as a muscle tissue the next structure up in terms of size is organs and organs are made up of different tissues working together to perform a particular function for example the stomach and and then organ systems are lots of organs grouped together which work together to perform a function like the digestive system which we'll be covering and then the largest is an entire organism which means a living thing and organisms are made up of different organ systems working together and an organism could be a human for example so then if we move on to some examples of each of these structures you need to know about tissues in animals organs in animals and organ systems in animals and the first organ system is the human digestive system now it does say in the spec that you need to know the digestive system in the level of detail from keystage 3 but I'm guessing you might not remember that so I'm going to go through that information so you know exactly what you need to know for your GCSE exam so the first thing is what is the function the digestive system is made up of lots of different organs some of these aren't the digestive system we can see the lungs but we'll go through all of the ones which you need to know and the function is it breaks down your food from being large and insoluble molecules into smaller soluble molecules which can be absorbed into the bloodstream and then transported around the body any food that isn't absorbed after digestion then forms the feces and is removed as waste so the structures of the digestive system or the organs that you need to know are all the ones listed here so you might want to screenshot print it and have it in your notes or you can copy out the table or turn it into flash cards so we've got the mouth that is where we have mechanical digestion which means chewing to break apart the large molecules you also have some chemical digestion where we have enzymes which we'll talk about later in the video such as amalay which help to chemically break down some of the large molecules the salivary glands which we can see just here next to the mouth those are producing and releasing saliva which contains the enzymes that do some of the chemical digestion then the food is swallowed and it goes down the esophagus which is this tube here ignore the spelling in this picture this is the UK spelling of esophagus and that's just a tube that connects the mouth to the stomach then we get to the stomach and this is where the food is mixed or churned up and it's mixed with acid hydrochloric acid but acid is sufficient and that is to partially help to break down the food but also it's to kill any microbes like bacteria that might have been in your food to protect you from getting an infection and getting ill you also have some enzymes which are there to digest proteins once that is happened the food then passes into the top of the small intestines and that top part of the small intestines is known as the jod denim the next B is the jenim here you don't need to know that you just need to know about the jod denim that is where the food passes into and at that point we have the gallbladder shown here in green and the pancreas you can just about see it here behind the stomach showing in yellow those both connect to the duod Denim and release liquids into it now you need to be more specific than just saying liquids you need to say what those contain so the pancreas is going to be releasing or secreting liquids that contain enzymes and we'll cover these three enzymes later on in this video now this bit here about the B carbonate ignore that cuz what you actually need to know is down here linked to the liver and the galbladder and that is the liquid known as bile which is actually like bright green sort of color and the liver is where bile is produced the galbladder is where it is then stored and then it's released into the jod Denim and we'll be learning about what bile is but in brief it emulsifies fats which means splitting up into smaller droplets and also it is what neutralizes the stomach acid so when the contents of your stomach then moves into the duod denim it neutralizes that contents so that you don't get damage to the small intestines because your stomach can withstand the hydrochloric acid it's got a special layer but the small intestines doesn't have that so it would be damaged if we didn't neutralize that stomach acid as it travels in with the bile then small intestines the rest of the small intestines this is the main site of digestion with enzymes and it's also where the Digest food gets absorbed one key adaptation of the small intestines is the inside of this is highly folded and that is creating these structures known as Villi which increase the surface area for the absorption of the digested food once most of that content is then absorbed it will then transport into the colon or large intestines and this is where water is absorbed so that's the main role of thege large intestines and then anything that hasn't been absorbed then gets stored in the rectum and then eventually it is released from the body as feces through the anus so we talked about enzymes quite a bit there but we haven't said what an enzyme is so here we can see an image of an enzyme enzymes are biological catalysts and that means they speed up chemical reactions and it's known as biological it's happening inside of an organism they are essential for metabolic processes which if you aren't sure on the definition of metabolism that means the sum of all the chemical reactions in a cell or organism so in other words it's all the chemical reactions that happen in your body so enzymes are speeding up all of the chemical reactions that happen in your body and they are able to do this because of this unique shape part in them known as the active SES and this is where substrates can bind if they are complementary in shape meaning opposite in shape and there is one enzyme to catalyze every different reaction because there are lots of different enzymes which all have a different shape active site which is specific and only complementary to one substrate so let's have a look at how The Binding of the substrate to the complementary shaped active site speeds up these chemical reactions so that active site is the key point on enzyme and enzymes are large proteins which are folded up to make these unique 3D shapes and that's how we get this unique shaped active site and as I said that active site will only be complimentary in shape to one substrate and when we say complement we mean opposite so they fit together like pieces in a jigsaw and that is what is going to happen to enable the enzyme to speed up the rate of reaction so when that substrate binds that is then going to put some tension on the substrate so it will help to break it apart using less energy and therefore it be a quicker reaction now this is actually explained in more detail through this model known as the lock and key model or the lock and key Theory and this is explaining how enzymes speed up or catalyze reactions so first of all it is suggesting that the enzyme in particular the active side is like a lock and the substrate is like a key and only if that key is perfectly complimentary in shape to the lock which in this case is the substrate being complimentary in shape to the active sight can it fit in when it does fit in it is known as an enzyme substrate complex so in terms of the lock and key Theory this is when the key would be inside of the lock and this term enzyme substrate complex is is almost always worth a mark in exam questions linked to enzymes so write this down put it on a flash card make sure you know that Q term and any enzyme question you get where possible try and use it and if you use it correctly then it'll be worth a mark and that's because when this enzyme substrate complex forms that is what is catalyzing the reaction because it's helping to break apart the substrate or if it's a reaction where you're joining two molecules together it's holding them in place and making it easier for the body to form so this is allowing the enzyme to carry out its function once the substrate has been broken apart or joined together depending what type of reaction it is we then get an enzyme product complex and it's slightly different shape to the substrate so it then is released once the products are released from the active SES the enzyme can then be reused to catalyze that reaction again assuming you still have more substrate to react with so the enzyme is unchanged it does doesn't get used up and it's just there to catalyze the reactions now enzymes are affected by certain conditions and you need to know how temperature and pH affect enzyme activity so first of all let's have a look at temperature starting with what happens if the temperature gets too hot enzymes have what is known as an Optimum temperature and the word Optimum means the best temperature for the enzyme so basically the temperature it works fastest at is the optimum and for most enzymes the optimum is around 37° C because that is body temperature and enzymes are catalyzing the reactions inside of the body so that is typically your Optimum temperatures above the optimum so higher than 37 will start to denature the enzyme and what D nature means is it changes the shape of the enzyme and if you change the shape the enzyme the active site will change shape and once the active site has changed shape that's what we mean by an enzyme denaturing now this means that the reaction won't be catalyzed anymore because if the enzyme's active site changes shape the substrate can no longer bind because they're not complimentary in shape and you don't get enzyme substrate complexes forming therefore the rate of reaction will decrease and if all enzymes do nature then the rate of reaction will stop now if it's too cold enzymes do not denature what happens at the colder temperatures is the enzyme and also the substrate won't be moving very quickly because if it's cold the molecules will have less kinetic energy which is basically movement energy and if your enzyme and substrate are moving around slowly inside of your body or inside of your cells then they're less likely to come into contact with each other and Collide so that the substrate can Collide into the complement shaped active site so that means we get fewer enzyme substrate complexes and again the rate of reaction will therefore be lower so two key things to make sure you do not make a mistake with number one is if it is cold enzymes do not denature it's just you're less likely to have successful collisions because the molecules are moving less number two is enzymes are not living things they're protein molecules so enzymes cannot be killed if an enzyme isn't working you have to say they've been denatured so next is looking at the effect of pH enzymes work best again at a particular pH which is known as the optimum pH but in this case enzymes have different optimal phes because different parts of your body are at different phes so for example in the stomach the pH in your stomach is around pH one or two it's very very acidic so the enzymes that you find in the stomach like proteas which digests proteins they have Optimum phes of one or two but then the enzymes that you find in the small intestines the small intestines is about ph8 so they have an optimum pH that they work out of eight so whatever the optimum is if the pH is either too high meaning it's too alkaline or too low meaning it's too acidic that causes the enzyme denat as well so it also causes the enzyme to change shape changing the shape of the active site preventing enzyme substrate complexes and therefore reducing the rate of reaction so just to summarize some of those key points we said our definition of metabolism that's the sum of all chemical reactions in a cell or body and metabolism is reliant on enzymes now some examples are breaking down large molecules which we're going to have a look at in digestion some of them though involved helping to build large molecules so one of the Year 11 topics is protein synthesis and then we've got energy transfers so when you learn about respiration and photosynthesis they also involve enzymes so all of these are enzyme controlled reactions and all of these make up metabolism so so let's have a look then specifically at enzymes in digestion and these are enzymes responsible for breaking down molecules specifically they breaking down the large ins soluble food molecules into smaller soluble molecules and those smaller molecules are then absorbed into the bloodstream and transported around the body so here are the enzymes you need to know we're going to go through all of them in more detail but again just in case you wanted to screenshot and have it all on one page you can add it to your notes Here is your screenshot shots but I do just want to point out for the amalay one if you are taking a screenshot can you add next to it carbohydrates and amalay is an example of a carbohydr so here's our summary but let's go through each one number one are the carbohydr enzymes and these digest carbohydrates and they break down or digest those carbohydrates into smaller soluble molecules which are simple sugars so amalay is an enzyme which is an example of a type of carbohydrates so the site of production meaning where are these enzymes made so some are made in the salivary glands which then get secreted into the mouth to work there some are produced in the pancreas which then gets secreted into the duodenum that top part of the small intestines and some of them are made in the small intestines and then are used in the small intestines as well so here's a very simple word equation an example of a carboh hydrate is starch starch is digested by amalay and it's digested or broken down into the simple sugar molos so one little tip to try and help you to remember new terms in biology is any word that you see in biology that ends in ASE means it's an enzyme so carbohydr that literally means it's an enzyme that breaks down carbohydrates so amalaye is an example of a carbohydr enzyme and it ends in ASC the second digestive enzyme is protease again ending in ASC so we know it's an enzyme and it digests protein so the name of that enzymes implying what they are digesting proteins are polymers and they are digested into the smaller monomers that make them up which are amino acids the places that prote are made are the stomach so we have some digestion of proteins happening in the stomach the pancreas which will release the enzyme proteas into the duodenum which is that top part of the small intestines so there'll be some further digestion of proteins in the small intestines and then the small intestines themselves also produce proteases for further digestion there so here's a simple word equation protein which is our large insoluble food molecule that is digested into into its monomers the amino acids which are smaller soluble molecules and that is done using the enzyme protease the last one you need to know is lipase ASC at the end so know it's an enzyme lip at the start because it's lipids lipids is the name for things like fats and oils and lipids are digested into two molecules we get glycerol and fatty acids so a lipid is split into those two different molecules lipase is produced in the pancreas and it's secreted from there into the duodenum which is part of the small intestines and also you get even more made in the small intestines so the only place lipids are digested is the small intestines and here we have a simple word equation the lipids are broken down into glycerol and fatty acids with the help of the enzyme lipase sometimes pronounce lipay but you can say either or just make sure you spell it correctly now there's a little bit more to lipid digestion you need to know about and that is the role of bile which we briefly talked about when we looked at the overview of the digestive system bile is not an enzyme but it does help with the digestion of lipids so bile is this green liquid that is made in your liver it then gets stored in the ghoul bladder and from there it's released into the duodenum which is the top part of the small intestines and B does two things number one B is really Al line so that means as you add bile to the top of your small intestines and you have the stomach acid and the contents of the stomach pouring in at that point as well that strong acid from the stomach will mix with a strong alkaline which is bile and it neutralizes that hydrochloric acid that stomach acid and it actually makes it slightly alkaline we get about ph8 you don't need to know that though and that is now the optimum pH for the enzymes in the small intestine such as lipase so that's one of the jobs it neutralizes the stomach acid to get the optimum pH for enzymes to work at the second job is bile emulsifies fats and what that means if I had to do a quick diagram if we imagine a fat droplet whether it's a droplet of oil or it could be a droplet of a solid fat you've got one large droplet one large sphere bile is able to break that one drop let into several smaller droplets and that's what a multipication means it's when you separating that large lipid droplet into lots of smaller droplets and the reason this is an advantage is if you've got lots of small droplets that now means you've got a greater surface area for the enzyme liay to act on so let's imagine here we could maybe only fit one enzyme on but now now we'd be able to fit lots of the enzyme lipase on we've got a greater surface area so that's going to speed up the rate at which lipase can digest the lipids so let's have a look then at the products of digestion we said from digesting carbohydrates you get simple sugars and one of those simple sugars is glucose glucose can be used in your body to build new larger carbohydrates or a lot of it is used immediately in respiration to release energy we also had amino acids which were produced from digesting proteins and those are used to synthesize which means to create new proteins in your body and your body is actually about 50% proteins if you were to remove all the water and that's because things like enzymes muscle tissue antibodies which you'll learn about later these are all proteins so amino acids are essential and then finally the glycerone fatty acids once those have been absorbed into the bloodstream they can then be converted back into lipids which are used for things like making your cell membranes and also energy storage so we then move on to the next organ system which is the circulatory system and the main organ that you learn about in the circulatory system is the heart the heart is a muscular organ and it pumps blood around the body as part of a double circulatory system we're going to come on to that Concept in a few slides time the main function then of the circulatory system is to transport oxygen and nutrients around the body and when we say nutrients that's things that we just saw in the products of digestion so glucose amino acids fatty acids glycerol so that cells have everything they need to be able to release energy or to create new substances but we also need to remove waste products so it doesn't become toxic in the body so things like carbon dioxide need to be transported around the blood to get to the lungs so it can be exhaled so here is the root that blood takes but before we go through the root let's just have a look at the key structures the heart is made up of four chambers which basically means rooms so four spaces the top two are the Atria or Atrium for singular so we've got the right atrium and the left atrium and just as a note when you write it down you have to imagine that if you were to pick up that picture and hold it against your chest that is what we're considering the left and the right not how it looks to you looking down at it that's why that side says the right the bottom two Chambers which are larger those are known as the ventricles so here is our right ventricle and and then on this side we have the left ventricle so those are the four chambers of the heart you also need to know the four blood vessels that are attached to those four chambers so the right atrium the blood vessel attached to it is known as the vena Cara now this is Latin Vena means vein Cara means body so the Vina Cara is the blood vessel carrying blood from the rest of the body into the right atrium coming out of the right ventricle we have the pulmonary artery wherever you see this word pulmonary in biology that means it's attached to the lungs an artery is a blood vessel that carries blood away from the heart so the pulmonary artery is a blood vessel carrying blood away from the heart and taking it to the lungs then we have the left atrium going into the left atrium is the pulmonary vein so we know this must have come from the lungs because it's got the word pulmonary in it and vein those are blood vessels are transporting blood back into the heart I always say think it's got the word in in it it's taking the blood back into the heart and then lastly we have the aorta this is the blood vessel it's an artery carrying blood away from the heart and to the rest of the body so those are the four key blood vessels that you need to know the four chambers a few other things just to point out which are visible in this picture are we can see we've got what's labeled heart valves so this flap here and here that is a valve we've got them here these two flaps here as well and here valves we're going to talk about a bit later but just in brief they can close to make sure blood flows in the correct Direction and only in One Direction around the heart the last thing I just want to point out is the thickness of the muscle so look at how thick the muscle is in the left ventricle wall compared to how thick it is in the right ventricle wall and this is because the right ventricle is pumping blood we said up here to the lungs and the lungs are right next to the heart so you don't need to have muscle Contracting with that much force to pump the blood to the lungs so this enables us to pump the blood at a lower speed lower pressure so that you don't damage any of the blood vessels in the lungs and also so the blood flows slower so there more time for gas exchange but the blood that is in the left ventricle and is then pumped out of the aorta that's going to be transported to the rest of the body so it's going to have to go from the the heart all the way down to the cells right at the tip of your feet and to do that it needs to be pumped out at high force and high speed so to be able to pump it at high Force you need to have thicker muscle so it can contract more powerfully so that's why the left ventricle has thicker muscles it's so that it can contract with more force and therefore pump the blood out at higher pressure final thing I just want to point out is these arrows are showing the roots that blood takes we'll talk through it here in this diagram or flow diagram here but you also see it's color coded so you've got blue arrows versus red arrows the blue arrows mean that this is deoxygenated blood and that's because it's blood that has been delivered from the body where the cells have used up all the oxygen in respiration and it now needs to go back to the heart to be pumped to the lungs to become oxygenated again and because the pulmonary vein is delivering ing blood into the heart from the lungs got that word pulmonary that means if the Bloods just come from the lungs it's going to be oxygen rich or in other words oxygenated blood and that's what the red arrows are representing it's oxygenated now this here talks us through the root of the blood through the heart but this is imagining if we were looking at the Journey of a single red blood cell the root it would take all the way around because in reality as we can see here those two arrows both pointing it blood is going to enter from the pulmonary vein and the venne Cara at the same time so blood enters both sides at the same time and it's pumped out of both sides at the same time but if you had to do a long answer question describing the root it often says a start point and you have to describe the whole journey so if we start the venne Cara where we can see here that takes blood into the right atrium then from the right atrium it's pumped into the right ventricle then we can see from the right ventricle the blood is pumped up and out of the pulmonary artery that is then taking the blood to the lungs from the lungs it gets oxygenated and then the blood re-enters through the pulmonary vein into the left atrium from the left atrium it's then pumped into the left ventricle the left ventricle contracts with the most Force to create high blood pressure pumps the blood up and out of the aorta and that then takes the blood to all the body tissues and then we go right back to the start again the venne Cara so that is the structure of the heart some of the details about it and also the roots that blood takes through the heart so this information here is actually summarizing some of the previous facts I'd already annotated on so just to summarize those the right side of the heart shown in blue is handling deoxygenated blood the left side of the heart has oxygenated blood gas exchange we're going to talk about in more detail when we get onto the lungs that is happening in the lungs and the left ventricle has the thickest muscular wall because it has to contract with more Force to pump blood out of the heart at higher pressure so it can reach all of the body cells so next then let's have a look at the heart valves and I've actually already annotated this onto the picture and highlighted them and we've briefly mentioned it but we'll go through this in more detail so heart valves are basically small FL s and when they close together it stops the blood going backwards so they're a bit like doors making sure that the blood travels in one direction through the heart and we have them between the Atria and the ventricles on both sides and we have them between the ventricles and the artery so the pulmonary artery and the aorta so the whole point is valves prevent the backf flow of blood that's the key phrase that is used in mark schemes and the reason this is important is it makes sure that the blood flows continuously in One Direction and that's important for the inici transport of oxygenated blood to your respiring cells so there's like your mark scheme answer for describing and explaining the role of heart valves next then is the coronary arteries these are actually arteries on the outside of the heart so far we've just been describing the inside of the heart or the chambers inside but the coronary arteries are blood vessels that run on the outside of that heart muscle and the coronary arteries supply the heart muscle with oxygen and glucose which are needed by the heart muscle so they can respire and release energy cuz the heart is constantly Contracting and relaxing but for a muscle to contract and relax it needs energy and that energy comes from respiration and respiration needs glucose and oxygen so if you get a blockage in one of your coronary arteries which is what this image here is zooming in and representing these fatty deposits blocking it so that blood can't flow through anymore that can result in a heart attack because it would mean your heart muscle isn't getting oxygen and glucose that means it can't respire that means the muscles can't contract and that's what a heart attack is it's when parts of or all of your heart muscle isn't Contracting anymore so a double circulatory system then at the start of this section I said that the circulatory system is known as a double circulatory system so what that means is there are two circuits that the blood travels through and therefore the heart has blood traveling through it twice so the first circuit we can see here is the pulmonary circuit and if you remember we said pulmonary means it's attached to the lungs so this is the circuit where the blood goes from the heart to the lungs back into the heart so that's just one circuit that the blood blood takes the second circuit is the one that goes to the body known as the systemic circuit but it'd be fine to just call it the body circuit or to say it's the circuit where the blood is transported around the rest of the body and then it goes back into the heart so the advantage of this is it means that we can transport the deoxygenated blood to the lungs to become oxygenated and it means then to the rest of the body cells we can transport the oxygenated blood which is a really efficient way to transport oxygen so we have really oxygen-rich blood rather than mixing the two together and that would just dilute the amount of oxygen you actually have present it's also really helpful because it means that the blood can be pumped to the lungs at a lower pressure than the blood that is pumped to the rest of the body and that's good because we want the blood to go to the lungs at lower pressure so that the blood flows through the capillaries in the lungs slower and that means there's more time for oxygen to diffuse into the blood and it also means if it's going at a lower pressure it's less likely to cause damage to those blood vessels in the lungs another Advantage is it means that the blood can be pumped out of that left ventricle through the aorta to the rest of the body at higher pressure and that means that the oxygenated blood is going to be able to reach all of those respiring cells in the body now sometimes you have have issues that go wrong in the heart and inside of your heart you naturally have a group of specialized cells or in other words a tissue because a group of specialized cells performing a function that is a tissue known as the pacemaker and you find them in the right atrium of the heart one of those top Chambers in the heart and the role of these pacemakers are that they cause this release of electrical activ ity is this wave of electricity goes across the heart and that is what causes the heart muscle to contract and the freequency so how quickly the pacemaker cells release this wave of electrical impulse or wave of electricity across the heart is what determines how quickly your heart beats so in other words the Pacemakers are setting the pace of your heartbeat so they are dictating how quickly your heart beats and this is really important because first of all it ensures you have a regular heartbeat but also it's coordinated to your needs so if you are resting the pacemaker will release that wave of electrical activity slower if you are doing exercise it will release that wave of electricity faster and in that way it can control how quickly your heart beats in some cases though People's Natural pacemaker cells stop working and as a result you might get an irregular heart rhythm and that could be dangerous it means you're not then actually pumping blood around the body at set frequencies that you need for respiration so when this happens you can use an artificial Pac maker so an artificial pacemaker this is going to be implanted just under the skin usually around your neck at your collar bone and then you just have a little cable that goes through blood vessels to reach the heart and the artificial pacemaker will release that wave of electricity instead and that will now be what is controlling your heart rate so that would be the solution or the treatment if your natural pacemaker cells weren't working correctly anymore so you've just got a little summary box there on the difference between your natural pacemaker cells and because it is a group of cells this is an example of a tissue versus an artificial pacemaker right we then move on to next organ system which is the respiratory system containing the lungs so the human lungs are vital organs in the respiratory system and this is where we have gas exchange happening so oxygen is going to diffuse from the lungs into the blood and carbon dioxide is going to diffuse from the blood back into the lungs to be exhaled now this process is known as gas exchange because you you are exchanging gases gas from the air is exchanging the oxygen into the blood and the gas Caron dioxide goes from the blood back out again from your lungs and exhaled specifically the gas exchange happens at a structure known as the alveoli so we're going to have a look at the structures of the lungs in more detail one thing though I just want to point out before we do this a really common mistake that is made is that because this is known is the respiratory system people think that inhaling and exhaling is respiration sometimes and that is not true respiration is a chemical reaction that releases energy what happens in the lungs is gas exchange and breathing is what ventilation is and once you've breathed you can then have gas exchange okay so the key structures we'll start with the trachea which is this pipe we can see here so this is a tube also known as the windpipe which has cartilage rings so we can see these Rings here cartilage is a slightly flexible but also hard material so if you feel your nose your ears you don't actually have bone in your nose or your ears but they have a solid sort of structure to them and that's cartilage so your nose shape is cartilage your ear shape is from the cartilage and you also have rings c-shaped rings of cartilage in your tra and that's to make sure that your wind pipe your trachea is permanently open and that the tube doesn't get sticky and stick together so this is the tube that connects to your mouth on your nose and it carries the air as you inhale to your lungs there's also tiny hairs that line the inside of the trachea known as cyia and these hairlike structures they move back and forth in this sort of sweeping motion and what then happens is the mucus that also gets produced by cells lining the trachea and the whole point of mucus is it's this thick sticky substance so when you inhale any dust that you might have inhaled or any microbes that you might have inhaled they should get stuck to that thick sticky mucus and then the cyia which are these tiny hair like structures which are sweeping backwards and forwards they actually end up moving the mucus up your trachea and that's then when you get that stion like the tickly feeling in your chest that you need to cough and that's what you're doing you're coughing up the mucus to remove any mucus that might have dust or microbes to protect your lungs the traa then Branch into two which are the Brony so you have a right broncus is singular Brony is plural so there's our right bronchus and here is our left broncus so that's our two branch and tubes from the trachea they then trans transport the air into these smaller branches known as the bronchioles and at the end of the bronchos you have these Bunches of alvioli so in alvioli you have them in these bunches it looks like grapes but a single alvioli or alveolus for singular if we zoom in this is what it looks like and this is literally where gas exchange happens so the alvioli is just an EMP air sack this bit here in pale pink that is the alvioli and it's just made up of a single layer of cells making a wall and because it's such a thin layer it's just a single layer of cells on the outside this is a capillary blood vessel and we've got red blood cells flowing in the blood around it but because the Alvi is only made up of one layer of cells that's a really short diffusion distance so oxygen if I just draw this on oxygen from well let's not do yellow let's pick a different color let's go black um oxygen which would have been in that inhaled air that's going to diffuse into the blood from the alvioli and it's a really short diffusion distance it only has to diffuse through a single layer of cells that makes the wall of the alvioli a single layer of cells that makes the wall of the capillary and then it is in and same for the carbon dioxide that is diffusing out I'll do the label here cuz I can't fit it in it's got a really short diffusion distance we're going to talk about some other advantages on the next slide other adaptations but the final thing we can see here in terms of adaptations or structures present I should say is that the alvioli are surrounded by lots of capillaries and as we zoom in we can just see one capillary here but you have lots of capillaries surrounding all of the Alvi the Alvi is literally the site of where gas exchange happens gas exchange just means the diffusion of the gases so oxygen diffusing into the blood and carbon dioxide diffusing out of the blood so then if we have a look at the adaptation so you might want to screenshot this so you've got this as a table to put into your revision notes we've talked about the structures and we said that the air travels from the mouth and nose through the trachea through the Brony to the bronchioles and then the alv which are the air sacks where gas exchange takes place gas exchange is is diffusion so oxygen diffuses from the alvioli into the bloodstream carbon dioxide diffuses from the bloodstream into the alv and because it's diffusion we need to think about what are the key adaptations that we see to increase diffusion one of them is having a large space a large surface area so you actually have millions of those alveoli in your lungs so you'll have millions in this lung Millions on this lung as well and because there are so many that creates a massive surface area for this diffusion this gas exchange to occur we talked about the thin walls already the rich blood supply so this is where I said that the alvia are covered in a network of capillaries now this is an advantage because it's a short diffusion distance because the blood stream is right next to it but also it helps to maintain a concentration gradient because as soon as the oxygen diffuses into the blood blood is then transported away and that then helps to maintain a concentration gradient finally is ventilation which means inhaling and exhaling and because we're constantly breathing in air which will have a higher concentration of oxygen and exhaling air which has a higher concentration of carbon dioxide this ventilation is maintaining the concentration gradient as well so those are our key features how they are maintain maining or increasing the um rate of gas exchange so that takes us on to the blood vessels then which are still part of the circulatory system there's three main blood vessels that you need to know arteries veins and capillaries all three of them have a different structure and function so let's have a look one thing though just to point out as a way to help you to remember this is looking at these two things so arter Aries I always think a away arteries carry blood away from the heart veins have the word in in them they're carrying blood back into the heart or back to the heart so that's how to remember which way around it is in terms of their functions so here we have a picture of an artery if it was sliced open and you looking at the cross-section and the same for the vein and the capillary and we've got our summary table here so first of all we've just said this arteries is a away carry blood away veins is going in so it's going towards the heart and capillaries that is what is connecting together if I just go back here the arteries to the veins and it's where we get exchange of substances happening so the thickness then arteries have the thickest of the walls veins have a thinner wall but the thinnest of all of them is a capillary and that's because a capillary is just made up of a single layer of cell the pressure of the blood is high in the arteries it's lower in comparison in the vein and it's at its lowest in the capillaries then if we look at the size of the Lumen which means the space in the Middle where the blood flows through the arteries have a narrow Lumen the veins have a much wider Lumen it's not always perfectly circular as well and then the capillaries have the narrowest of them and in fact they're so narrow that you can only fit one red blood cell through at a time so it really slows down the speed of the blood flowing through the capillaries because they're so narrow then if we think about valves which we said with those flaps that prevent the back flow of the blood you only get valves in veins in terms of elastic fibers we only have elastic fibes in the artery and veins not in the capillaries and you get mainly the elastic fibers in the artery have a much thicker layer and that's because they have to be able to stretch and recoil as the blood is pumped through them at high pressure finally then we've got the functions so the artery is transporting that oxygenated blood under high pressure to the rest of the body the veins are transporting deoxygenated blood at lower pressure back into the heart and the capillaries are the site of exchange so for example gas exchange at the alvioli so little bit more then on what a valve is it's a thin but it's still strong flaplike structure that you have in veins but also we looked at them in the heart and they ensure blood flows in One Direction only so they prevent the back flow of blood they also help to maintain the flow to the Heart by closing and open at the right time that is going to make sure the valves help to continue moving the blood to the heart so they are really important in the heart and the veins overall to help prevent the back flow and to make sure blood is moving efficiently through the circulatory system so then if we move on to the Bloods Bloods is an example of a tissue because it's groups of different cells working together to perform a particular function and these are the four components of blood that you need to know you need to know their appearance adaptations that they have and the function that's a key thing is the function so if you want you can screenshot this and then you can have that summary table in your notes so so the plasma this is the liquid part of the blood and if you actually were to separate it out you just had the plasma the plasma is this sort of yellowy straw like looking liquid so it's a watery liquid and it contains all of the dissolved substances like it might have dissolved proteins it might have hormones it might be waste in there like carbon dioxide so it's there to help to transport different nutrients and waste in the blood the red blood cells are responsible for transporting oxygen now although it says and carbon dioxide there ignore that that's actually something you don't need to know until a level so you just need to know that they transport oxygen they are B concave or in other words dis shaped but by concave is the phrase that they would want for the exam which means they dip in on both sides so it's concave on this side but also on that side so it's by concave if you were to look at it from that angle and that helps make it to be a little bit flexible but also increases the surface area so you get more oxygen diffusing in we also have white blood cells you learn more about this in the Infectious Disease topic topic three but they are larger than red blood cells IR regular in shape they're flexible they can surround and engulf pathogens but their main role is to defend the body against infection and disease so it could be making antibodies antitoxins or engulfing pathogens and then lastly the platelets you don't really need to know this information here about adaptations or appearance but they are fragments of cells and they help to clot the blood so that is what causes blood clots if you have a cut that's why you eventually stop bleeding is platelets trap all the red blood cells and help the blood to clot now one thing it says in the specification that you need to be aware of is that if someone lost a lot of blood maybe due to a medical medical condition or a severe injury they can have a blood transfusion which is when you get someone else's blood transported into your body basically a blood transfusion but you need to be aware of or be able to evaluate the risk of someone having a blood transfusion and you aren't expected to know these reasons off by heart but if they gave you this information they'd want you to be able to say whether it's good or bad and obviously the main good thing is it's going tol replace the blood loss so you'll be replacing the plasma the red blood cells the white blood cells the platelets the risk though could be you are at high risk of transmitting infectious disease because if someone is giving their blood maybe they had HIV or another virus and it wasn't detected then you now have that virus in your body sometimes people have an allergic reaction sometimes people might reject the blood meaning the immune system realizes it wasn't part of their body originally and it causes an immune response but that's why they do blood type matching to try and reduce the likelihood of that happening and then sometimes iron overload I haven't actually seen this ever come up on the gcsc so the top three are the main ones that might come up as an application question so then we move on to what could go wrong so coronary heart disease is an example of cardiovascular diseases cardiovascular means any disease linked to the heart or blood vessels so it could be coronary heart disease or it could be heart failure and you need to know a very little bit about this mainly looking at how it can be treated and it could be treated using certain drugs Mechanical Devices or even having transplants so the drugs would be statins Mechanical Devices would be things like stents and then transplants could be a valve or it could be a heart transplant now you can screenshot this to have this as your summary but I'm going to go through them all in more detail now so um coronary heart disease this is if you have a buildup of this fatty material blocking your coronary arteries and therefore oxygenated blood and glucose aren't reaching the muscles so they can't contract we talked about that a little bit earlier so what you can do then is one option is using something called a stent which are small tubes that get inserted into the arteries those coronary arteries and then you can either use something to inflate and push that tube outwards um or you can actually leave that metal mesh inside as well and essentially what it is doing is pushing those fatty deposits backwards and making the artery a hollow Che again so the advantages are that stents can often be inserted with very little surgery and it can restore the blood flow so it reduces your risk of a heart attack the downside though is it is surgery and all surgery comes with a potential risk of you getting infected and you also might need to have this treatment repeatedly so restenosis you don't need to know that as a term all it means is you might have to have that procedure again which again puts you a higher risk of infection again then Statin so this is a drug treatment so these are drugs that reduce cholesterol in your blood and cholesterol is what makes those fatty deposits so the advantage of this is it's not invasive you don't have to have any surgery you just take them as a tablet they're preventative so they can help reduce the progression of heart disease and the likelihood you might have a heart attack but the downsides are they can have some side effects such as muscle pain digestive problems liver damage sometimes as well um and also you would have to take statins for the rest of your life to have that benefit continually then if we think about faulty heart valves so heart valves can become faulty meaning they either don't open or close properly so you're not preventing the back flow flow of blood so the treatments then are you could have a valve replacement and that could be a biological valve made from animal tissues such as pig or cow or it could be mechanical so that would mean that it's made from synthetic materials which means it's not from a living thing so it could be like a metal or some sort of carbon synthetic material so the advantages are it can improve the heart function and reduce symptoms of valve disease it is a long-term solution as well disadvantages though because it would involve surgery there's a risk of infection and kind of contradicting that long-term solution is is a long-term solution if you're going to have the mechanical in particular but biological valves sometimes do wear out and you might need to have them replaced again particular if you had this procedure done when you were quite Young next then is heart failure and this occurs when the heart is unable to pump blood effectively leading to poor oxygen supply to the organs and tissues so you would either need a heart transplant or an artificial heart so in terms of heart transplants you are reliant on their being a donor the advantages are it is going to restore normal heart function and therefore significantly improve life expectancy and quality of life um it can be a long-term solution often it might last for 10 to 20 years and you might need to have another trans plan though disadvantages is the big one availability of donors there is a shortage of suitable heart donors which means there might be a very long wait time there's also risk of rejection when you have any kind of transplants so you'd have to wait for a donor that matches your tissue types and also take immunosuppressant drugs which basically means it suppresses so it lowers your immune response to try and stop it from rejecting the heart an artificial heart is a mechanical device which can be used to keep a patient alive while they're waiting for a human heart transplant so advantages are it is readily available and it can keep you alive long enough while you're waiting for a heart transplant um it is temporary though it allows the heart to rest so it is going to reduce the strain on the body but it's not going to be like a lifelong solution and that takes us here so it's a limited lifespan the artificial Hearts aren't a permanent solution risk of complications as well there a risk of blood clotting now for all of these treatments that we've gone through it would likely come up as an application question where they give you more details and you have to pick out the pros and cons and write an evaluation next time is looking at health and disease and our definition of health is the state of physical and mental well-being so it's not just looking at the absence of disease But it includes being free from any physical or mental health concerns and there's two types of diseases we can consider communicable which basically means infectious or non-communicable which are the ones that are linked to lify and environmental factors and you've got some examples written here as well so the relationship between health and disease is something that you need to be aware of and the following factors can impact physical and mental health so diet stress and life situations so a poor diet and maybe lack of exercise and high stress as well all of those can increase the likelihood of you developing a non-communicable disease such as heart disease so that would be physical health stress and maybe life situations we've got examp examples like if you became unemployed or poverty or there was some trauma that can contribute to mental health conditions such as depression and anxiety there's also some interaction between different diseases meaning if you have one disease it can increase your risk of developing a different disease so for example if we look at immune system defects people who have a disease resulting in a weakened or impaired immune system such as those with HIV which then can develop into AIDS are more susceptible to get infectious diseases because their immune system can't fight off the pathogens virus and cancer there's a link here as well because some viruses like the human papiloma virus or HPV for short are linked to certain Cancers and HPV is linked to cervical cancer pathogens and allergies as well so sometimes if you're infected with a pathogen particularly in young people like infants and babies it can trigger an allergic reaction and that's when you then start to see skin rashes and then physical illness and mental health so if you have a severe physical illness or maybe a long-term health problem that can negatively affect a person's mental health and it could lead to depression anxiety or other psychological conditions as well you also need to know the impact that non-communal diseases can have so for example cardiovascular disease or type 2 diabetes lung cancer liver disease these are non-communicable diseases meaning they're not infectious but they can have big impacts first of all on an individual level so a person who might have one of these diseases might have a reduced quality of life chronic pain chronic means it's ongoing they might have limited Mobility they can't move around as much and emotional distress in terms of the impact on a local community if you have a lot of people so high prevalence of a non-communicable disease that can put a strain on the Health Care system so maybe in that local community the GP surgery is really really busy and there's too many people that need support or it could link to maybe social care needs as well or maybe in that local community there's just not enough people working because they're ill and that's going to affect the economy on a national level governments face High health care costs for treatment but also for prevention it costs as well if there's a lack of Workforce because they're too ill to work and that can have an impact as well on the economy and then a global level non-communicable diseases are responsible for a significant portion of global mortality so deaths creating challenges in healthcare funding Public Health initiatives to try and consider how to overcome them and economic inequalities between countries as well so here's just a summary then of some lifestyle factors which can increase the likelihood of you developing certain non-communicable diseases so diets we can see that there's a link here to high sugar high fats increas in the likelihood of obesity cardiovascular disease also um Diabetes Type Two Smoking is linked to lung disease and cancer alcohol excessive alcohol consumption can lead to liver disease affecting liver function brain function and if you're drinking when you're pregnant that can lead to fetal alcohol syndrome obesity linked to type two diabetes um exercise so if you are doing regular exercise that actually reduces your risk of cardiovascular disease um carcinogens these are basically chemicals that increase the likelihood of mutations happening in your DNA so if you're exposed to carcinogens then that could increase the likely of you developing cancer so carcinogens include things like um in cigarette smoke there's carcinogens this here should really be split because radiation isn't a carcinogen because carcinogen means chemical but as a separate Factor being exposed to ionizing radiation also increases your risk of cancer so all of this talk of risk then is looking at risk factors and these are elements that increase the likelihood of you developing a disease doesn't mean you definitely will just means you're more likely to so here are some so we've got life-based ones that we just looked at environments so whether you're exposed to harmful substances and pollution or radiation and a causal mechanism links risk factors to disease so we do know that smoking can cause lung cancer it's also a risk factor because it doesn't mean you will always get lung cancer but it increases your risk and we do know that the carcinogens and cigarette smoke can cause lung cancer we also know being obese increases your risk but being obese can actually um result in diabetes type two diabetes and we know alcohol can cause liver damage but again it doesn't mean that it will always happen it increases your risk and we know that alcohol can cause these um conditions and the same with the other three so the correlation doesn't prove it will always cause a disease but we do know that there is that association between them next is looking at interaction so many diseases result from interactions of multiple factors so there's usually more than one cause cardiovascular disease for example might be because someone smoked they had a high fat diets really stressful life not exercising and all of those together interacted to result in the cardiovascular disease cancer might be triggered by maybe your genetics partially but also exposure to carcinogens or ionizing radiation and unhealthy lifestyle choices and that leads us on to cancer and you do need to know a little bit about cancer so cancer is the result of changes in the cells in particular it's changes to the DNA in the cell which results in uncontrolled cell division so your cells just constantly divide and because they are constantly dividing it results in a tumor and a tumor is a mass of abnormal cells basic like a ball of cells that shouldn't be there and it's because your cells are continually divided making more and more cells in a place you don't need those cells and that uncontrolled cell division is because of mutations or changes in your DNA there are two types of tumors that can form a benign tumor and a malignant tumor and here is our summary of the differences between the two the main thing that you need to be aware of is that benign means it's not a cancerous tumor malignant means it is a cancerous tumor and malignants or cancerous tumors can invade neighboring tissues so we can see here in a malignant tumor shown in here those red cancer cells those can break apart from the tumor and then they might travel in the bloodstream and then Lodge into another part of your body and cause another tumor which is nam as a secondary tumor benign tumors though are encased in this capsule so they're stuck all together it can only impact the exact location it's in which means it's makes it easier to try and remove whereas to try and remove a cancerous or malignant tumor is really difficult because the cells might have already spread to other parts and it's really hard to know if you've definitely removed all the cancerous cells without removing some of the healthy body cells as well so risk factors for cancer some of these we've actually talked about already because it links to both lifestyle but also there are some genetic factors but here's just a short list so smoking Diet alcohol consumption obesity sun exposure these all increase the risk of different types of cancers which if you want you can pause and have a read through then we've got the genetic risk factors so some cancers such as breast cancer ovarian cancer prostate cancer there is a genetic link where you might have inherited some DNA which means you're more likely to get a cancer than another person is who doesn't have that particular gene or that section of DNA so understanding cancer in the context of risk factors then is the main thing is cancer is often caused by a combination of the risk factors rather than just one of those things we saw on the previous slide so it could be a mixture of lifestyle and genetics or a combination of the different Lifestyles so for example a person with a family history of breast cancer might have an increased risk of developing breast cancer because of their genetics but if they maintain a healthy lifestyle that helps to lower their overall risk so Lifestyle Changes such as quitting smoking or improving diet can significantly lower the risk of many types of cancers even if you had genetics that put you at higher risk so the last bit of this topic then is looking at some plant tissues organs and organ systems so plant tissues just as a quick reminder a tissue is a group of cells with a similar structure and function and plants have special tissues that work together to carry out essential functions such as F synthesis transport and growth so here is a selection of the tissues that you need to know again I've done it as a table so you can do a screenshot and then put it into your notes as well so root hair cells these are the cells that have got that long protruding part to provide a really large surface area and it's where you have the absorption of water and mineral ions the the xylm tissue is the one that's the hollow tubes and it's where you get the continuous column of water forming flm tissue you have those Civ plates so it's Hollow but you have the Civ end plates in between and this is where the sugars are transported merry stem tissue is responsible for the plant growth by dividing so that's way of your stem cells and then guard cells and stamata the guard cells are on the lower side of a leaf and they create this hole which is known as the stata now all of these are actually covered in more detail in my GCC topic one video because this is where you learn about the specialized cells and also stem cells you go into this in more detail in the topic one video if you want to have a look at that you can or you can just read through this screenshot it as well so the leaf is a plant organ and as a reminder organs are groups of tissues that work together to perform a particular function and the tissues inside of a leaf are the epidermis tissue Palisade misil spongy maphil xylm and flum and the stamata and the guard cells so here we can see that cross-section through the leaf so the epidermis you have a top so upper and also a lower epidermis that is often waxing and it's there to prevent water loss from the leaf the Palisade misil is this layer here we have lots of long oblong shaped cells with loads of chloroplasts in and the chloroplasts are able to absorb light energy which is needed for photosynthesis the spongy misil is this tissue layer here where you have lots of spaces where it spaces for gases to diffuse into so it helps with gas exchange in the leaf the xyum and FL which we can't actually see in this image but the xylm transport water and minerals and and the FL transport transports the sugars smarter and guard cells we can see better here because it's the guard cells that are controlling whether the stomat is open or closed and the stata are the holes so we have two guard cells next to each other and when they're turgid which means they're hard they're filled with water they Bend and curve and that creates this opening which is the Tomato where carbon dioxide can diffuse into and oxygen can diffuse out of water vapor also diffuses out which isn't beneficial but that's why the guard cells can control whether the stom is open or shut so a little bit more here the sto or stomata for plural are the small openings on the leaf and that is where we've gas exchange but also water vapor can evaporate the guard cells are controlling the opening and closing of that stamata and in bright light guard cells are going to be absorbing water and that makes them turgid or rigid so they Bend and curve and they open and that then means plenty of carbon dioxide can diffuse in through the stat and be used in photosynthesis in dark or dry conditions the guard cells lose water so they become flaccid or unfirm and that causes them to close together and that closes the stamata so you don't get water loss transpiration this is the process of water movement through a plant and it's basic evaporation from the leaves through the stomata it's essential for transporting water and mineral minerals through the plant and actually also helps to cool the plants so here's the process water is absorbed by the root hair cells in the soil by osmosis that water then moves into the xylm from the roots and then it moves up the xylm as this continuous column of water through those hollow xylm tubes and that is known as the transpiration stream when the water reaches the stat and the leaves the water will then evaporate and in the form of water vapor it diffuses out through the stamata and that's what we mean by transpiration that loss of water at the stamata will then pull on that continuous column of water so you get even more water being pulled up the xylm so factors that can affect the rate of transpiration then because it's basically evaporation you've got to think of factors that affect evaporation so that can be higher temperatures because that means the water molecules will be moving faster they've got more kinetic energy and therefore evaporation happens faster high humidity that means you've got lots of water vapor in the air and that reduces the concentration gradient and therefore you have less evaporation and transpiration low humidity means you don't have much water vapor in the air so you have a steeper concentration gradient and you get more transpiration air movement is linked to this idea that should all be highlighted there um but if you've got lots of air movements it's really windy that's going to blow away air that has lots of water vapor in it and that way you're constantly maintaining a steep concentration gradient between the leaf and the air outside and increases transpiration light intensity will increase transpiration and that's because that high light intensities it causes the stata to open and that means you've got a larger surface area for the water to evaporate out of so that then takes us to the end so it's time for you to test yourself pause this slide if you want to have a go I'm not going to talk through the questions and answers I'm literally just going to show them so that you can have a go so here are the questions pause screenshot have a go and here are the answers to those 10 questions again pause screen shot and you can have a go at marking it three is all about infection and response and we start with looking at communicable diseases which is an infectious disease and looking at the different pathogens that you need to know pathogens are microorganisms so they're microscopic living things but the difference between a microb and a pathogen is it is a microb that could cause an infectious disease and that is in animals and imp plants these diseases can spread between organisms which is why they called communicable diseases pathogens need a host which is an organism they infect to survive and the host provides the right conditions and the nutrients such as glucose for the pathogen to grow and reproduce there's two main ways that they can make you ill number one is producing toxins bacteria release poisons which is what a toxin is and these toxins can damage your cells and your tissues causing the symptoms that you might get such as a fever pain or even swellings the other way that they can cause harm is through attacking your cells and viruses do this by invading your body cells to reproduce and then as they reproduce they damage and destroy your cells and that can also lead symptoms and illness the body does have natural defenses such as your skin and your immune system to protect against these pathogens which is what we're going to be going through later in this topic but first let's have a look at the pathogens in a bit more detail so we already said what a communicable disease is and they're caused by different pathogens the pathogens that you need to know are viruses which you can see here in the top right these reproduce quickly inside of cells and that is how they cause damage bacteria also reproduce quickly about once every 20 minutes they reproduce and they can release toxins and because you have so many bacteria producing those toxins it can make you feel ill prst which we can see here these are a group microorganisms that can cause disease some are parasites meaning they live inside of a host and cause harm and that is malaria as an example which comes up later in this topic and then lastly A fungi and they can grow on the surface of organisms and they sometimes releas toxins as well so the way that these diseases are transmitted or in other words how the pathogens can be spread between different organisms varies depending on the type of pathogen it is and the disease that they cause the three modes of transmission that you need to know about are direct contact transmitted through water or transmitted through air or droplet infection and this table summarizes what these types of transmission mean so for direct contact this means that it is spread the pathogen is spread through physical contact and that could be between touching an infected person an infected surface or object and this can be the case for plants as well if you have an infected Leaf falling onto a healthy plant we've got an example of athletes foot so that spreads through sharing towels that then will have the fungi on them or walking barefoot and damp places where you might have the fungus there already so to prevent getting infections through direct contact you should avoid sharing personal items and wash hands regularly water is when the pathogen is carried in contaminated water so that would enter your body through drinking or it could be through bathing and then if you had a cut in your skin it might be able to enter that way color is an example and that is spread through drinking unclean water so to prevent this there are strategies such as boiling water before drinking it or using purification methods and ensuring good hygiene and sanitation lastly we've got the air droplets this is when the pathogen spreads through air in tiny droplets when an infected person coughs or sneezes and this is how the common cold flu covid-19 are spread it's there inhaling those virus containing droplets so to prevent the spread cover your mouth when you are coughing when you're sneezing wearing masks prevents the spread as well and in crowded areas try and make sure that you are having as much ventilation as possible so here we have a little bit more detail on preventative measures we did mention some of those on the last slide but have a look at some of them in more detail good hygiene so we've got washing hands but in an exam need to be specific washing hands with soap because just with water isn't going to remove the pathogen you have to be using a soap for vaccines that is going to prevent the spread of infection as well because if you have fewer people able to have that infection then there's few people to pass it on using disinfectant so this is a chemical that kills bacteria and you use it on surfaces so you could be cleaning surfaces regular with disinfectants to kill bacteria it can also destroy some viruses and therefore if you're touching that surface you aren't going to be touching anything with pathogens on food safety is another one because if you aren't cooking food through properly particularly meat then pathogens such as salmonella can be in that food and then when you eat it the pathogen gets into your body the final example we've got is quarantining people who are infected so that means people that are infected they'd be kept separate from healthy people so they can't transmit that pathogen and that's something that we saw a lot during covid-19 so that's how we can reduce the transmission of the diseases you also need to know about the pathogens in a bit more detail and some different examples so starting with viruses then they will invade and reproduce within a host cell when we say hosts cell that means the individual that they are infecting and they have to be inside of a host to be able to replicate and because the virus reproduces in side of body cells that then causes the body cells to burst and it causes damage it also means it's quite difficult to treat the virus because in order to treat the virus you would have to destroy your own body cell antibiotics which are a type of medicine do not work against viruses so treatments to try and remove a virus from your body actually focus on preventing infection in the first place because it's very hard to treat a virus once you're infected you have to just rely on your own immune system to destroy the virus so things like vaccines prevent infection and for certain viruses there are antiviral drugs as well which will help the three examples that you need to know are measles and HIV which both affect humans and then tobacco mosaic virus which affects plants next if we go on to bacteria bacterial diseases are caused by bacteria that pathogen which are single celled microorganisms and unlike virus is bacteria can live and reproduce independently in the right conditions so that means they don't have to be inside of the host to reproduce and for that reason bacteria can actually survive on surfaces some bacteria are harmless and some actually beneficial to humans and other organisms but if it does cause harm it's known as a pathogen and you do get pathogens that are bacteria that infect both animals and plants the two key ways that they cause harm are by their rapid reproduction increasing the number inside of you and then you've got so many of them producing toxins which are poisons and those toxins could damage your tissues or they could cause symptoms like we talked about earlier like fever vomiting and even diarrhea the examples that you need to know are two that have infect humans so salmonella and goria the next group that we're going to look at are fungus and fungal diseases are caused by fungi which can be a type of pathogen and that could be mold yeast mushrooms and you have some that attack animals and also plants fungal infections are often spread by spores which are a bit like tiny little seeds in fungi and they can travel in the air water and also they can remain on surfaces and the key one that you need to know is a fungal disease that infects plants known as Rose black spot lastly then we've got the protists and these are single celled microorganisms they not bacteria they're not viruses or fungi some of them are parasites which means they have to be inside of a host to survive and then cause harm the one that you need to know about is malaria now as we went through all of those I said the ones that you need to know about and I said the names of them and whether they infect animals or plants but this slide now gives you the table of how they're transmitted the symptoms that they can cause and the prevention and and treatment so I recommend you pause screenshot and then you've got all of this information for your notes these are just key facts that you're going to need to remember for the exam so you've got the disease the pathogen that causes them how they're transmitted symptoms and also how you can prevent and treat them you might want to also add whether it is a plant or an animal that is being infected and that was on those previous slides if you want to add that in as well so next time we're going to have a look at humans are able to defend themselves against pathogens and there's two key types of defenses we have something called the nonspecific defense system this is like your first line of defense that would be the barrier and protect against any potential pathogens and that could be preventing them getting in but also how they're destroyed if they do get in and it's called non-specific because it's going to be the same strategy the defense system no matter what the pathogen is next we've got the immune system and this is a targeted defense that fights specific pathogens if they do manage to get into the body so let's have a look at some of these non-specific defense systems and also the barriers you have to entry so non-specific defenses are there to block or remove pathogens before they can cause any harm to your cells and tissues these defenses are always active and you do not need to recognize the particular pathogen in order for them to work so we can see here we've got the skin the skin is a physical barrier that stops the pathogens from entering the skin also has sebaceous glands within it which produces oils and some of those oils are able to kill bacteria if you get a cut in your skin then you will quickly form a blood clot and then a scab and that is to prevent your barrier the skin physical barrier from having any holes in which could then enable a pathogen to enter next time we've got the nose this contains hairs and mucus that can trap dust but also bacteria and viruses to prevent them from entering your lungs and causing damage you also have that reflex of sneezing or you might blow your nose to remove any mucus in your nose that would have potentially trapped pathogens within it next we have the trachea and Brony which are part of this breathing system they are lined with mucus and also cyia which are hairlike structures the mucus is a thick SI thick sticky substance which will trap any dust but also bacteria and viruses and the cyia are these tiny hairlike structures that move in this sweeping motion so it's a bit like they are a broom sweeping the mucus up and out of the trachea and you then end up coughing it or you might swallow into stomach either way is going to prevent it from getting to the lungs and therefore causing any damage to the lungs lastly the stomach the stomach has hydrochloric acid within it which is a very strong acid so we just said that the cyia will sweep the mucus up and you might cough it out or you might swallow it if you swallow it and it's going into your stomach your stomach then has hydrochloric acid within it which can kill most pathogens so it's going to help to destroy any pathogens in swallowed mucus or in any food or drink that you have eaten now if a pathogen does get past those responses we then move from what was non-specific to specific defense against pathogens and this is where your white blood cells come in so your white blood cells roles are to help to destroy pathogens and therefore prevent damage to your cells and tissues and there's three key things that white blood cells do number one is phagocytosis and this is when a white blood cell can move around or engulf a pathogen and once it's engulfed the pathogen it releases enzyme to destroy that pathogen such as a bacterium and then it's destroyed and it can't cause harm white blood cells can also produce antibodies and antibodies are these structures that are complementary in shape to antigens which are structures on the outside of pathogens so your white blood cells produce antibodies the pathogens have antigens on the outside and when the antibodies bind to those antigens it makes it easier for these white blood cells the fagio sites to locate and destroy the pathogen lastly there's antitoxins and we talked about how bacteria produce toxins these poisons which cause harm so white blood cells can also produce antitoxins which are complimentary in shape to the toxin which means it binds to them it therefore stops the toxin from binding to your body cells and that means the poison that toxin can't cause harm so here we have the information I was just saying now written out so if you want to pause take a screenshot you can then add that into your notes or turn it into flashcards those extra details going through what phagocytosis antibody production antitoxin production are and how they help to destroy pathogens so another way to help prevent the spread that we talked about was having a vaccine so vaccines are a preventative measurement and they protect individuals from Contracting a particular disease it involves introducing small amounts of either dead or inactive versions of the pathogen that causes the infection and that could be through an injection these pathogens that are injected in can't actually cause the disease themselves but they can trigger an immune response so let's go through how a vaccine Works CU this is quite a common long answer question so mark number one would be for saying that in a vaccine a dead or in active form of a pathogen is injected into the body the immune system will then detect that injected pathogen and the white blood cells respond the response of the white blood cells is to produce specific antibodies and the mark scheme is really particular that you do have to say specific antibodies because it's all to do with complimentary shapes fitting together the body then remembers that particular pathogen and therefore the specific antibody to create so if you are reinfected with the same pathogen later on after your vaccine the immune system is able to respond really quickly and create large quantities very rapidly of that specific antibody that means that those antibodies are going to bind to the antigens on the pathogens and that means that the pathogen can't cause harm and it will be destroyed before it can cause any illness or in other words it's destroyed before you get any symptoms or you might just get very very mild symptoms rather than getting the fullblown symptoms so a bit more then on how that works after you've been vaccinated what happens is we said if you are reinfected you get large quantities of the antibodies being produced very very rapidly if you're reinfected and that's what this graph is showing us at this point where it says initial exposure what that would mean is that is when you were injected with the vaccine so that was the first time you were exposed to that pathogen it was just a weakened version of it and your body's respon is over time you've produced a small amount of antibodies and that would be enough to just remove the small amounts of inactive or dead pathogen that was injected but then your white blood cells have a memory of that particular path and antibody to produce so if later on you do get infected with the actual pathogen that would be our second exposure because your white blood cells already have a memory of that pathogen and the antibody it's able to much much quicker and that's why we've got a much steeper curve here much quicker and in larger quantities to produce those antibodies so that the pathogen will be destroyed before you get any symptoms now what that means is you have this longterm immunity to that particular pathogen and you having these vaccines or a population as a whole not only does it protect you from getting that disease it helps to protect the whole population because of something called herd immunity now you don't need to know literally that term herd immunity but you do need to know that if enough of the population are vaccinated against a particular disease it will reduce the spread of that pathogen and that is because if a large enough amount of people are vaccinated that means all of the unvaccinated people which would be very few they're the only ones that can now get infected and pass on the disease so if most people can't get the disease and get infected they can't spread it that should therefore protect the people in the population who are not able to have vaccines and that is sometimes pregnant women or very early newborn babies or anyone with a weakened immune system might not be able to have a vaccine so if a large enough proportion do have the vaccine it protects those vulnerable people and that's why there was such a drive during covid to try and encourage people that are healthy enough to have the vaccine to have the vaccine to try and protect themselves but also to protect the entire [Music] population now another treatment is antibiotics now these are medicines that only kill bacteria they do not work against viruses and that is because viruses reproduce inside of cells but also viruses aren't actually living things so the way the antibiotics work don't work on viruses so the way that antibiotics work on bacteria are that they can either break down the cell wall of the bacteria and that causes them to be destroyed and also some antibiotics will stop stop the bacteria from growing and reproducing so different antibiotics are used for different bacterial infections and they do work in different ways now before antibiotics bacterial infections like pneumonia and tuberculosis were often fatal and since the 1940s when antibiotics were discovered antibiotics have saved millions of lives but there has been a downside to this because the misuse and overuse of antibiotics has resulted in some bacteria being antibiotic resistance so let's go through what that means some bacteria have mutated and what that means is their DNA so their genetic material has changed that's what a mutation is it's a change in the DNA and that change happened to give the bacteria a slightly different either cell wall structure or way that they grow reproduce and as a result the bacteria that had that mutated DNA were now not affected by the antibiotics or in other words they are resistant to them so the antibiotics will not kill that bacteria now these mutations randomly happen so it's completely spontaneous or random it's due to chance but the overuse or misuse of antibiotics made this process happen more quickly and the reason for that is if there was a bacteria that had this mutated DNA which meant it could now survive if antibiotics were taken if there was someone who was taking lots and lots of antibiotics even though maybe they didn't need them for example when they were infected with the virus that means the antibiotics would be killing all of the nonresistant bacteria and just the resistant bacteria are left in your body and now they don't have to compete for the resources they can reprodu uce and Thrive and suddenly you now have a large population of resistant bacteria now you don't actually need to know this but an example is MRSA which you may have heard of so MRSA this long name you definitely don't need to know but methylin resistant staf coccus Aurorus that's just one example of a bacteria that is now resistant to many different antibiotics so how can we try and reduce this first of all only use antibiotics when necessary and by that we mean it has to be a bacterial infection and you should only use it if your own immune system isn't able to destroy the pathogen itself you should also always complete the full course of antibiotics so if you're given antibiotics to take twice a day for seven days but you felt better by day four or five you should still take all of those antibiotics to kill all of the bacteria and also doctors now avoid prescribing antibiotics and if it's a viral infection they won't new antibiotics also need to be developed to help to replace the ones that no longer work because bacteria are resistant to them there's another type of medicine that you need to know about which are painkillers so paracetamol ibuprofen aspirin you might be familiar with and these do not kill the pathogen so they're not going to cure any illnesses but what they do is relieve symptoms as the name suggests they kill pain so not only can they reduce pain but some painkillers also bring down a temperature so if you've got a fever some of them also reduce swelling so inflammation in the body unlike antibiotics though as we said painkillers do not treat the cause of their disease so let's have a look at how some of these drugs were discovered and then we'll go on to development so for our drug Discovery most of our early medicines were coming from plants and microorganisms and that is a particular chemical that you might find in a plant or a microbe and there's three examples that you need to know digitalis and that comes from this flower here a fox glove that is a chemical that is now used as a heart drug aspirin that is a painkiller originally found in willow bark and then penicillin which is an antibiotic it was actually the first discovered antibiotic by Alexander Fleming and that was in this mold penicilium mold modern drug development though is actually more so focused on synthesizing which means creating new drugs by Chemists in these huge pharmaceutical companies so it's less so about discovering something by chance in plants or in fungi it's all about using your Chemistry knowledge to design a particular drug that might treat the disease however many drugs do still have the same start point of knowing a particular naturally occurring chemical in plants or microbes and then scientists can edit and modify the chemical to try and make it more effective so how are new drugs tested then because once a drug has been discovered it can't actually be given to people straight away and it often takes around 12 years between the discovery of a drug before that drug is commonly prescribed and that's because there has to be several tests that are done to look at first of all toxicity that means testing is the drug toxic is it going to be harmful and cause side effects efficacy that means does the drug actually work so is it going to help to cure or prevent the disease and then lastly the dosage you have to make sure that you know exactly how much different people should be taking so that the drug is effective but also so it is safe and not causing harmful side effects so there's two main stages to these drug testings pre-clinical trials comes first and that means trials that you do before you test it on any humans so step one is just testing it in a lab and you'd be testing this new drug on just groups of cells or tissues and then live animals so things like mice for example and the point of these stages are to help to look for any potential side effects so it's testing for toxicity and looking at how the drug interacts with body cells if the drug passes this stage meaning it didn't cause any harmful effects to the cells or the live animals then you go on to step two which is clinical trials which is now when we test the drug on humans so one once it's past the animal and cell stage which is preclinical testing then you test on humans so this involves testing healthy volunteers and also small groups of patients as well to test is it safe on humans and also is it effective so these clinical trials on humans so testing on humans are split into different phases phase one you give a very low dose of the drug to healthy volunteers and we do it as a low dose because if they're are harmful side effects at least you've only given them a low quantity so hopefully it doesn't cause too much harm and it always starts on healthy volunteers phase two the drug is then tested on a small group of patients and again they will be volunteers but they are patients and this is to see if the drug does actually treat the disease and we only test a small number of people just to make sure it's not going to be potentially harmful and if it is it's only affected a few people rather lots of people and then lastly phase three this is where we move on to larger trials on many patients this is going to help to determine the optimum dose there's also this concept of double blind trials or you might have heard of a placebo and this is when you do all of those drug trial stages the clinical trials on humans some patients receive the actual drug that you are testing While others get a placebo and a placebo is a fake or a dummy treatment so you would give them what looks like the medicine except it doesn't have the treatment in at all so for example if you were giving someone a tablet which was the new drug you would give someone instead a tablet that looks identical but it would just be a sugar pill so that's all it contains sugar and in these double plins neither the patients nor the doctors know who has received the real drug and that's why it's called double blind because the patients and the doctors are blind they don't know who has had the real drug versus the placebo now you do have this information written down it's just you find that information out afterwards or you have an independent person who will have that information and the whole point of doing this is to avoid bias because if you are told you now have this new drug sometimes the power of the mind is enough to make you start to get better or feel better rather than the drug itself and with the doctor's knowing without realizing they might ask leading questions so they might say to the group with the drug are you feeling better now whereas they might say to the group that have had the placebo have you noticed any change and just those slight differences repeatedly in the way you might phrase it is enough to potentially sway how someone feels now as well as these double blinds to try and make sure that we've got really accurate information there's also something called peer review and peer reviewing is once you've done all of these clinical trials and you've got all your information and you might come to a conclusion as to whether the drug is effective or not you also have to have other scientists check the work to make sure that they agree the method that was used is valid and that they agree that the scientists have analyzed the data correctly so results of drug testing and trials are published only after peer review and this is to make make sure we have accurate and reliable Data before new drugs are approved so peer review also helps to prevent any false claims or even errors that people might be trying to put out there from their research this next section on monoclonal antibodies is only on the higher tier so if you're not doing higher tier this section is not going to be relevant for you and you can skip to plant disease so what are monoclonal antibodies these are identical antibodies that's the clonal part they're identical and they target one specific protein and that's what the one the mono is one so identical antibodies that Target one specific protein antigen they're used to identify or treat specific cells in the body so how they are made is another common long answer question it could be four marks it could be more I've split up here as if it was a four mark question so let's go through it first of all why do we want to make them well we make them in large quantities and we're going to look at the uses on the next slide but we want to create a large quantity of these monoclonal antibodies so Step One is stimulating the mouse lymphocytes because the mouse is going to be like our production Center so a mouse is going to be injected with the antigen that you want to make antibodies against so it's going to be inject into the mouse the mouse's white blood cells specifically a lymphocyte bodies against that antigen meaning compliment in shape next step is we need to create what's known as a hybridoma cell hybrid meaning two different things fused together and what we're fusing together is this lymphocyte body and a tumor cell so those two are fused together to make a hyoma the reason for that is this lymphocytic antibody and the tumor cell rapidly divides so that now means we've created a hypom cell which will rapidly divide so we create large numbers of identical lymphocytes that produce the specific antibody that same specific antibody that we want and we then allow enough time for it to produce lots of those antibodies collect them purify them and we now have a large quantity of monoclonal antibodies so the uses of those monoclonal antibodies they could be used in pregnancy tests you don't actually need to know the details of how it would work in a pregnancy test it might come up as an application question but the idea is you are creating monoclonal antibodies complimentary in shape to a hormone that you only make when you're pregnant and it's a way to identify if that hormone is in your blood you can also use them to measure substances in the blood so sometimes it might be for drug testing it could be to identify molecules in cells or tissues and sometimes it can be used to treat diseases as well because you could make these monoclonal antibodies complementary in shape to cancer so antigens on the outside of cancer cells and that would then mean that the antibodies are only attaching to the cancer cells and you can then attach a drug to the antibody so the treatment goes directly to that cancer cell so here we have it in a little bit more detail again like I've said previously you can pause screenshot and then you've got that extra information here if you want to add it to your notes lastly then you need to know about the advantages and disadvantages of using monoclonal antibodies the advantages are they are really specific which means they will only bind to one type of antigen and therefore you can use them as Really T targeted ways to identify molecules or to send treatment and that's what this next one is it can help to Target cancer cells so you send the medicine directly to the cancer cells through this monoclonal antibody and therefore it will destroy the cancer cell but it won't harm as many healthy cells and as we said it's useful you can use it in pregnancy tests to help diagnose um if you are pregnant diagnos isn't the right term for that but to detect if you're pregnant but also diagnose for disease diseases as well disadvantages is expensive to produce and it does require advanced technology they've actually found that using this as a treatment for things like cancer has had more side effects than they were expecting particularly allergic reactions and we've also got it's not widely used yet in terms of treatments it is in terms of testing for disease and pregnancy though the final part of topic three is on both the higher and Foundation paper but is not on combined science this is for biology only meaning the separate Sciences or triple science so detection and identification is one part of this topic that you need to know so how can you actually tell if a plant is infected and plants can also show visible symptoms when they are infected by pathogens like viruses bacteria or fungi or even insects which isn't a pathogen but they can still cause harm so here are your common side effects or symptoms you've got the visual here and then Al of the list so stunted growth just means it's not growing properly sometimes you see spots on the leaves so discoloration and in patches you might have areas of Decay where parts of the leaf or the plant are starting to die and break down you might have growths which mean these abnormal lumps which could be on the leaves or it could be on the actual stems as well you might get Malou formed stems or leaves so they have a different appearance it might be a bit twisted discoloration ation so they might be yellow instead of the usual green and then the presence of pests so if you can see lots of aphids for example that an indication that it is infected with aphids now these are the common plant diseases the symptoms and the causes that you need to know so you might want to screenshot turn this into flash cards or just have this table in your notes but tobacco mosaic virus we had come up earlier on that is a virus it causes these Mosaic patterns on leaves it stunts the growth Rose black spot is a fungal infection it causes these purple black spots on the leaves and in both of these cases because you are damaging the leaf that means you have less F synthesis occurring less glucose being produced less glucose for respiration that means less energy and the plant just isn't going to grow as much aphid infestation so aphids are an insect they're a type of pest this also results in stunted growth you might even get wilting which is when the leaves start to droop and you might get yellow leaves and the cause is the aphids are biting into the plant and they are feeding on the plant sap which is the sugary substances and if they're using up all of those sugars then that means the plant doesn't have the sugars like glucose it needs for respiration then we've got the two at the bottom which aren't infectious diseases these are deficiency meaning you don't have enough of something and nitrate deficiency is when a plant doesn't have enough nitrate ions which are an example of minerals that they get from the soil the nitrate ions are needed to make proteins so if you don't have enough nitrate ions in the plant it doesn't have enough proteins and that means it's not going to grow as much so you get this stunted growth it looks smaller magnesium ions again it's absorbed through the root hair cells from the soil and magnesium ions are needed to make chlorophyll which is the green pigment in Le this is why the symptom of magnesium deficiency is this yellow colored leaf and because it's not got chlorophyll it can't absorb light energy it's not going to photosynthesize as much and therefore it's not going to be producing the glucose it needs for respiration and again you will end up then getting a smaller plant eventually so how can plants defend themselves then cuz they don't have an immune system they don't have white blood cells but they are still able to defend themselves so you have physical defenses and those are for example the cellulose cell wall that helps to protect the contents of the cell leaves have a tough waxy cuticle to prevent entry into the leaf and also bark does start to peel off and as it peels off that means that any potential pathogens that might be on the bark or going to fall off you then have chemical defenses and some plants such as witch hazel which is what this picture here is showing you some plants produce chemicals which can kill pathogens lastly we've got mechanical defenses so things here like Thorns now Thorns do not defend against pathogens because pathogens are microscopic so a thorn is not going to do anything to them but what these Thorns do is prevent animals such as herbivores so larger animals that eat plants from being able to eat the plant so let's have a look at this summary here here's our type of Defense here's some examples and here is a description all of these examples of defenses you need to know so I've talked through some of them so we've got our physical ones which we saw on the previous slide with the picture and you've got the description we talked about having those chemicals and also poisons that can help to first of all the antibacterial chemicals will destroy pathogens but also some plants produce poisons which are toxic to animals and it prevents an animal from eating them mechanical we talked about the thorns and sometimes hairs but they're also other mechanical defenses some leaves will droop or curl when touched and when that happens it can scare an animal off CU it might think is another animal as well so it's to help to prevent herbivores eating them this is the same idea with mimicry mimicry is the fact that some plants actually look like dangerous animals or other plants do trick animals to avoid them from eating them so that takes us to the end of topic three pause now and have a go at these end of topic questions just to see how well you remember and have understood everything and then on the next slide we'll have a look at the answers any that you didn't remember or you got wrong go back and watch that part of the video again to try and help consolidate that information but you pause now I'm going to move straight on to the answers here are the answers for those 10 questions so pause Mark your answers and see how you did than for for gcsc biology first of all an overview of this topic because this is the one that explores how plants and animals obtain and use energy so we'll be looking at how plants photosynthesize and we'll be looking at how both plants and animals are going to respire and in fact all living things respire and they can respire aerobically and anerobic but we'll be looking at in animals the buildup of lactic acid in muscles and the effect of exercise so let's get into the main content starting with photosynthesis this is a process by which plants make glucose using light energy and because they're taking in energy that is why it's an endothermic reaction meaning energy is absorbed from the surroundings and the way it can take in energy is in the cells there are organel or subcellular structures known as chloroplasts and these contain a green pigment called chlorophyll which is able to absorb the light energy that light energy is then used in this reaction and you do need to know both the word equation and also the chemical equation so these would be good to turn into flash cards you could have one flash card showing the word equation and another showing the chemical equation now you don't actually have to write light energy within the equation like this it often goes over the top of the arrow like you can see in the image here also if you are new to my entire topic videos just to let you know the yellow highlights indicates key marking points so throughout all of this look out for those key marking points you should be including in your answers so you then also need to know about the rate of photosynthesis you can't be up here get we've already said one of the key marking points is it's an endothermic reaction meaning it needs energy taken in for the reaction to occur but it is also an enzyme controlled reaction and for that reason there are certain factors that will speed up or slow down the rate of photosynthesis one of those is temperature light intensity also has an impact because light energy is required for this reaction to occur carbon dioxide is one of the reactants so that is going to have an impact as well also the amount of chlorophyll because that absorbs the light energy so let's go through each of those in a bit more detail so if it came up in an exam you could explain why each of those factors affects the rate of photos synthesis and you could describe how so light intensity and it is key that you say intensity because that is referring to a bit like the idea of quantity of light but we don't say Quantity we say intensity instead light energy provid provides the energy needed for photosynthesis therefore if the light intensity increases that means you've got more energy for the reaction and the rate of photosynthesis will therefore increase but you can get to the point where if you increase the light intensity anymore it doesn't have an impact anymore because unless you also have Optimum temperature and enough CO2 you can't increase the reaction any further carbon dioxide then this is one of the reactants we saw that in the word equation so if you add more of that reactant the rate of reaction can happen faster but again that's only going to happen up to a set point CU beyond that you might have plenty of carbon dioxide but not enough light intensity and light energy for that reaction then temperature this links to enzymes because if you don't have a high enough temperature then there's not enough kinetic energy for those enzymes to form enzyme substrate complexes and if the temperature is too high that would Den nature enzyme so again you won't have the enzyme substrate complexes and that can cause the rate of reaction to drop to zero lastly the amount of chlorophyll that is the green colored pigment inside of the chloroplasts so if you have more of that there's more chlorophyll to absorb the light energy needed for photosynthesis and this links to topic three plant disease because if plants don't have enough magnesium ions to make chlorophyll then their leaves go yellow and that's going to affect the rate of photosyn is now this is one of the required practicals looking at how factors affect phot synthesis but in this video I'm just going through the theory but this is just to point this out that you can use this apparatus below to go through how to measure the rate of photosynthesis is affected by different variables and in this one we could look at how light intensity affects the rate so we can see we've got our setup our pond would be photosynthesizing the water bath is to control the temperature and we could measure the volume of oxygen produced over a period of time when the lamp is at different distances away and that's how it be varying the light intensity now this bit is for higher tier only and this is going into what I was talking about a bit more on the previous slides where we were saying when you get to a certain point when the light intensity is still increased but the rate levels off this is the concept of limiting factors so any of the four factors light intensity carbon dioxide temperature or chlorophyll may be the limiting factor at a given time and what we mean by limiting factor is that is what is currently limiting or slowing the rate of reaction and the limiting factor on these three graphs is always where you have this directly proportional relationship because as we increase the life intensity the rate is increasing so that means the life intensity is what is limiting it but where we see the rate pling or leveling off that must mean that something else is now limiting the rate because even though we're increasing light intensity still the rate isn't getting any higher so at that point the limiting factor must be either carbon dioxide concentration or temperature same idea here on the carbon dioxide graph at this point where we've got that positive correlation as we increase the carbon dioxide concentration the rate of photos synthesis increases and that means that carbon dioxide is the limiting factor at that point but where we see the rate leveling off or pling even though we're increasing the carbon dioxide concentration the rate isn't increasing so there now must be another Factor limiting the rate of photosynthesis it could be light intensity or temperature this graph isn't so much the limiting factors I mean it is at this point here we still got the positive correlation as you increase temperature the rate of fade CIS increases that is a limiting factor at this point the temperature but we have a difference because the rate drops off rather than leavening off and the reason the rate decreases is at that point the temperature is now so high that the enzymes that are involved in fath synthesis must have denatured now I've actually already talked through all of this if you want to pause so you can make notes and write it down or turn it into a flash card this is the information that I was just talking through to describe and explain the light intensity limiting factor graph and the carbon dioxide and then on the next slide we have the one for temperature next slide is also for higher tier only still linked to limiting factors and it's knowing that Greenhouse Growers and Farmers they will use this concept of limiting factors to try and maximize their yield which means the quantity of plant they are producing and if they're producing more plants that means they have more profit if that is what they're selling so they will need to consider is it worth them paying for lighting so that's electricity to increase the amount of plant growth and therefore what they have available to sell so essentially they have to see what costs them more the lighting and therefore you get more profit or will they actually get more money if they don't pay for lighting and they have slightly less to sell it depends how much the lighting is going to cost same idea if they're paying to heat it up to increase the temperature or if they're paying for paraffin which sh of fuel you can burn which will also increase the temperature but it makes carbon dioxide also so it's all to do with working out is it worth paying for the extra you've got to balance that out to see is it cost beneficial or cost efficient next F also higher tier and it's the concept of the inverse Square law so light intensity decreases as the distance from a light source increases so this links that required practical As you move the lamp which is your light source further away the light intensity will decrease and this relationship follows what's known as the inverse Square law which is this formula here that light intensity is proportional to 1 over distance squared so that is what you need to know the formula and what this means is that if the distance between a plant and a light source is doubled the light intensity reduces to a quarter and this diagram is visually represent presenting that so we now moving back to content that is for foundation and for higher and that is what is the glucose used for that is created in photosynthesis so number one some of that glucose can be converted into starch and it's stored for later use some of that glucose is used to produce fats and oils which again can be stored most of the glucose is used for respiration some of it is used to produce amino acids which can then combine with nitrate ions absorbed from the soil to create amino acids and proteins some of it is used to make cellulose which is what we find in the plant cell walls to provide structural strength we then move on to a respiration so this is the other chemical reaction you need to learn about and this chemical reaction occurs in all living organisms to release energy that is needed for metabolism this time it's an exothermic reaction which means when the reaction happens it releases energy or transfers energy to the surroundings respiration is essential because of that energy that is being released because the energy is needed for building larger molecules for example protein synthesis making those proteins from the amino acids it's needed for movement because when your muscles contract and relax it is using energy and keeping you warm as well because to maintain a constant body temperature in mammals and birds you need to respire to release energy some of that energy will be heat energy now one key thing I do want to point out as a really important examiner tip here is throughout this slide you'll notice I say release energy transfer energy at no point is it create or produce energy because you cannot make new energy you can only release or transfer it so it's really important you don't ever say produce or make energy it is releasing the energy there are two types of respiration aerobic this is the type that uses oxygen and it releases more energy because it can fully break down glucose and then anerobic respiration this is the type that doesn't use oxygen but it releases less energy because glucose isn't fully broken down so let's have a look at those two in more detail Arabic we said this is the type of respiration occurring when oxygen is available it completely breaks down glucose and therefore it releases large amounts of energy you need to know the word equation and also the chemical equation for this just like with photosynthesis and one thing you might notice is it is the opposite of photosynthesis photosynthesis was water plus carbon dioxide goes to oxygen and glucose aerobic respiration is the opposite it's glucose plus oxygen goes to carbon dioxide and water and that releases energy for the chemical equation I didn't actually say this for photosynthesis but it's the same concept because this is the reverse of photosynthesis in terms of balancing you do have to be able to balance it this is your chemical formula for glucose but all of the other molecules so oxygen carbon dioxide and water to balance it you put a six in front of those three so it's 666 that's how you balance these equations so key features of aerobic respiration we've said it's the type of respiration that releases energy using oxygen it releases more energy it produces carbon dioxide and water as waste products and it occurs in the mitochondria of the cells so that's specifically where aerobic respiration happens now let's move on to anerobic respiration in humans so anerobic respiration occurs when there's not enough oxygen available but you still have to respire because energy is required for that whole we talked about earlier but basically you need energy for All chemical reactions and if you doing intense exercise you are probably not going to be able to get oxygen into your body and to all of the cells fast enough to be able to continue to respire aerobically and that's why anerobic respiration begins because you still need energy but you don't have enough oxygen available and that will then result in oxygen being partially broken down the word equation for this is really short glucose is partially broken down and the only product is lactic acid this does release some energy but we don't put energy in the word equation because it's not a product we haven't produced it it's just released you don't need to know the chemical formula for this one so key features of anerobic respiration in humans is no oxygen is required less energy is released and that's because glucose is not fully broken down lactic acid is produced which is actually toxic and that acid can start to cause your muscles to fatigue which means they're not going to work anymore and that's because the lactic acid as the name suggests is an acid and that will start to denat enzymes and that affects whether the muscles can contract and relax so when that lactic acid does build up in the muscles when you're doing intense exercise that's why you can get muscle cramps or your muscles feel like they're tired and even though you're telling your arm to continue to contract when you're doing bicep curls or push-ups whatever it might be your body just won't do it anymore and that's because the muscles are fatigued and they physically cannot contract and relax anymore because of that lactic acid so after exercise oxygen is needed to break down that harmful lactic acid and it breaks it back down in the liver into carbon dioxide and water so it's no longer harmful and your muscles can recover and that's known as the oxygen debt which I'll be going into in more detail for higher te in a future slide anerobic respiration in plants and yeast is slightly different it's still when you have incomplete breakdown of glucose and it's when you don't have oxygen present but because plants and yeast which is an example of a fungus have different enzymes to animals you get different products so for both types of anerobic respiration in plants and yeast and also in animals you need to know the word equation but not the chemical equation and this process is known as fermentation when it's happening in yeast so key features then first of all you produce ethanol which is a type of alcohol and carbon dioxide and this is instead of lactic acid because it's making ethanol this is what is used to make alcoholic drinks so you would do fermentation which means allowing yeast to respire without oxygen and it will produce ethanol which is used to make alcoholic drinks it's also used in the production of bread because that is going to be harnessing that idea of the carbon dioxide to make the bread expand so this here actually just goes through that in a little bit more detail so the bread making the yeast respires anerobic that releases the carbon dioxide and makes the dough rise which is a better word than saying bread expand the dough is rising and alcohol production we've got the ethanols produced by that fermentation process and that's used to make beer and wine the alcoholic drinks we then move on to the next part of the spec for topic four which is response to exercise during exercise your body needs more energy because your muscles are Contracting and relaxing and to do that they require more energy so to supply this extra energy the rate of respiration has to increase and if you're respiring more the body responds in several ways to ensure that your respiring cells are being provided with sufficient oxygen so aerobic respiration can continue and also glucose cuz that is one of the reactants so the first change that we see is your heart rate increases and the reason your heart starts to beat faster is that means more blood is going to be transported around your body and if that blood has got glucose and oxygen in it that means you're supplying your respiring cells with more glucose and oxygen it also means that the waste products like carbon dioxide and potentially lactic acid are being removed from the cells more rapidly as well the next thing is your breathing rate also increases so you're breathing ventilating breathing in and out faster and that's so that you get more oxygen diffusing in and more carbon dioxide diffusing out of the alvioli your breathing volume also increases which means you're taking deeper breaths and that's so that a larger volume of air is inhaled into your lungs so that more oxygen will diffuse from the alveoli into to your bloodstream so all three of these changes are to try and ensure that aerobic respiration can continue for as long as possible however sometimes that is not going to be the case because if your body cannot supply enough oxygen despite all of those increases and changes that we just saw then anerobic respiration will start to occur in your muscles and as we said this is the incomplete break down of glucose you get less energy you get lactic acid and as that builds up it can cause muscle fatigue and pain and that's what stops the muscles Contracting as efficiently this next bit is for higher tier only and it's going into more detail about the oxygen debt so after that vigorous exercise where aerobic respiration wasn't able to continue because you didn't have sufficient oxygen being supplied to your cells you get what's known as an oxygen debt an extra oxygen is needed to be taken in SO gas exchange where you have the oxygen from the alvioli diffusing into the blood you need to get more oxygen so that you can break down the lactic acid so it can be removed from the body now lactic acid is broken down in the liver and it gets to the liver from those respiring cells in the blood so that blood transports the lactic acid to the liver and at that point in the liver if you have enough oxygen coming in it can break down lactic acid back to glucose and the amount of oxygen that is needed to break down all of that lactic acid after exercise is known as the oxygen debt so basically the body repays this oxygen debt by continuing to breathe heavily and more rapidly even after you've stopped exercising and that's what we can see here in the graph at rest we can see the oxygen consumption is lower you start exercising and the oxygen consumption is increasing it then reaches the maximum that you're able to consume after exercise this bit here is the oxygen debt the extra oxygen that is required to break down the lactic acid and then at this point you've recovered and gone back to your at rest State the final bit of this topic is metabolism and Metabolism this is a key definition is the sum of all chemical reactions happening within a cell or within an organism and all of these chemical reactions are enzyme controlled and they allow your body to either build or break down molecules as they need the energy for these reactions comes from respiration so let's have a look at some of the examples then of these synthesis reactions which means the reactions building molecules it could be building carbohydrates so glucose has come from digestion and then you've absorbed it could be converted into a larger molecule glycogen or if it's to do with lipids so fats and oils you absorb glycerol and fatty acids from digestion those could be converted into Li that are used for energy storage insulation and cell membrane and then last it could be making proteins from amino acid so the other set of reactions are those that involve breaking down molecules and respiration is an example of that because glucose is being broken down to release energy you can also have proteins being broken down when Ura is being formed so any excess proteins they actually can't be stored so they're broken down in the liver into Ura which then gets excreted and that excretion happens via the kidneys so that is it for topic four pause and have a go at these 10 end of topic questions to test that you have understood all the information and if there's any that you don't get right then go back and watch that bit of the video again so pause have a go I'm going to go straight onto the next slide which shows you the answers now so here are the answers have a go at marking them and see how you did and like I said go over them again if you need to so if you did find that helpful particularly the emphasis of key marking points key terms and examiner tips then head to the description because I have my full gcsc notes which go through key terms key marking points and there are examiners tips of what you should and shouldn't do to make sure you get the top marks as well as at the end of every topic there's a different set of 10 questions with the answers different to the ones that you see in these videos but that is it for today hopefully you found it helpful and I'll see you in a video soon [Music]