Transcript for:
AQA GCSE Biology Paper 1 Overview

hello loveles in this video Lauren my expert examiner is going to be taking you through the whole of AQA gcsc biology paper one now this is a lot you can use the time stamps and description to jump to the bit that you need to and make sure which bit is all noted down below also in the description you'll find the link to this year's predicted papers and then the walkthroughs of this year's predicted papers where Lauren using her expert examiner knowledge tells you what sort of things she would expect to see when she is marking the papers and then how you can lay out your answers to properly show off to the examiner that you know everything you know how to answer the questions based on what the command word is and any clues that the examiner has left you now to go with each section of this video over the website there's a free set of questions and some flash cards to make sure you get everything properly sorted and you're ready for that exam [Music] animal cell structure so we need to be able to label a basic animal cell and to know what all the parts of the animal cell does as part of the function of the cell so first up on the Outer Edge we have the cell membrane then we have the cytoplasm these little dots are representing ribosomes you're very unlikely to need to be able to label ribosomes in a diagram in the exam if they've got like lots of little dots all the way across the cytoplasm of the cell that's just to kind of represent the cytoplasm so it would be very specific and it look like special circles if they are talken about with ribosomes then we have the nucleus which is the biggest circle shape structure inside the cell and then we have the mitochondria so these are normally little kind of oval shapes with Wiggly lines inside that's on a diagram how you recognize that it's a mitochondria so the cell membranes function is to control the entry and exit of substances into the cell the cytoplasm is where chemical reactions happen inside the cell the ribosome's function is to do protein synthesis which means to make proteins the nucleuses function is to control the cell activities and the mitochondria function is it's where aerobic respiration happens and that provides energy for the cell now let's do the same with plant cells so plant cells also have a nucleus plant cells also have ribosomes they have a different oblong shaped structure to mitochondria which are the chloroplasts again these will look different to mitochondria they'll be oblong shaped but they not normally have little stacks of or dis shapes inside instead of Wiggly lines that's how you know it's the chloroplast then we have a mitochondria there's normally a large space area which is the vacu or the permanent vacu then the inner Edge this time is the cell membrane and the outer edge is the cell wall so I've filled in all of the functions of the parts that we've already looked at in the animal cell for the new parts the chloroplast function is to absorb light energy for photosynthesis this whole phrase is something you need to learn for the exam the permanent vacu contains cell SAT but its function is to be able to support the cell structure and the cell wall is strong because it is made of cellulose and that is also there to help the cell structure if you're comparing animal and plant cells there are only three differences which we've already spoken about to the three features that are found in plant cells that are not found in animal cells the cell wall the vacuo and the chloroplasts otherwise everything else is the same both animal and plant cells are classed as UK carotic cells the word eukaryotic is used to describe any cell that has a nucleus and that inside the nucleus is where the DNA is kept so because both plant and animal cells have a nucleus they are both eukaryotic cells procaryotic cells is a different type of cell these cells do not have a nucleus the name procaryotic literally means before the nucleus they evolve before a nucleus became structure in cells so they are without a nucleus an example of a prootic cell is a bacterial cell and their DNA is just found in the cytoplasm floating around not inside a nucleus we need to be able to label structures in bacterial cells as an example of procaryotic cells so they also have a cell membrane they inner layer around the edge they also have cytoplasm they have sometimes a different structure called a flagellum but not all bacterial cells have this we have little Loops called plasmids they have ribosomes their DNA or their chromosome is just floating in the middle in the nucleus as we said and they have a cell wall but it's a bacterial cell wall that is not made of cellulose so again I've put on the functions for the parts that we're familiar with for the flagellum again remember only some bacteria have this not all but it's used for moving around or swimming so the plas is a small extra Loops of DNA that often contain useful genes like antibiotic resistance the bacterial cell wall is for structure but also for protection we have to be able to compare prootic cells and eukariotic cells the main two differences are that there are no mitochondria or chloroplast in procaryotic cells and there is no nucleus one similarity with plant cells is that there is a cell wall in procaryotic cells however the cell wall in prootic cells is not made of cellulos so there is still a difference there these diagrams we' looked at very basic cell diagrams but most cells don't look like this cells change their size shape and internal or subcellular structures to carry out specific functions in organisms these are known as specialized cells there are some specific examples of plant and animal specialized cells that we need to know root hair cells are one example of plant specialized cells you can see here I've labeled all the structures we were labeling on our basic plant cell but there's some things that are different no chloroplasts this elongated shape for example all of this is to help the root hair cell carry out its function which is to absorb water and mineral ions from the soil syum and flm are two other types of specialized cell imp plants that we need to know they're highly specialized because they're very different from normal basic cells and they transport substances around the plant that's their function FL transports sugars and amino acids and the xylm transports water some animal examples we need to know so a sperm cell again I've labeled all the structures that we're familiar with from the basic cell but you've also got the fuelin which is allowing it to help it swim to the egg which is one of its main functions a nerve cell again very similar we can label all of those similar structures from the basic cell that we can see but the difference in the shape here the really long axon is to help transmit electrical impulses across long distances and finally muscle cells these cells have lots of mitochondria so although they look pretty basic actually they contain a lot more of mitochondria than a normal basic cell because they need that to provide the energy to contract which is their function you should be able to recognize these specialized cells but also be able to label all of the structures that we normally label in a basic cell on these cells that look slightly different cell differentiation cells become specialized through the process of differentiation this is where different genes are turned on or off in each cell to change their shape or the number of subcellular structures that they have and this is what allows them to become adapted to carry out a particular function undifferentiated cells so cells that have not yet differentiated to become specialized are known as stem cells so you can see here I have stem cell and then that stem cell can go through the process of differentiation to produce red blood cells or a neuron or epithelial cells or white blood cells or muscle cells or bone cells it depends on what that process of differentiation looks like in the cell determines what cell it's going to look like at the end differentiation is different between plant and animal cells plant cells mostly have the ability to differentiate throughout their whole life which is what makes cloning plants possible because you can cut off a piece of leaf or stem tissue and those cells can differentiate into root cells and you can create a new plant that way animal cells are not like that and they do not have disability most animal cells differentiate an early stage and once they're specialized very few of them can change or become stem cells again they just divide by mitosis to replace themselves so an example here is why differentiation of mitosis is important in animals is because we start off as a fertilized embryo and then that goes through mitosis develop of all of cells but all of these cells at this point are stem cells as the embryo starts to develop and grow into a fetus cells go through differentiation to produce all the different cells and tissues that the body needs Eyes Ears brain cells heart cells muscle cells bone cells all of those will be produced through differentiation and then once that's happened and you have all of the cells and tissues in the body that you need to have a full organism then we just go through the process of mitosis in order to grow and get bigger so to grow from a small fetus into the full size baby and then from a baby into an adult microscopes this is an optical or light microscope which you may have used in school initially they had mirrors which would reflect sunlight or lamp light but now we have electric BS in the bottom and the light travels up through a glass slide through objective magnifying lenses and into the eye of the person looking down the microscope the reason that we have microscopes is because they magnify images so what we're able to do is make a structure on a living material such as cells bigger and appear bigger than they actually are so that our eyes are able to see them we can calculate the magnification of a microscope by doing the image size so the image that we see from the microscope what we can measure in that divided by the actual size of the object we're looking at in real life so this is basically telling you how many times we have multiplied the size of the real object in order to be able to see it in the image Optical and light microscopes are great and they've been able to show us many things but we're only able to see like the nucleus inside a cell and just about mitochondria at about 1,500 times but really that's the level of detail we can go to anything smaller than mitochondria like ribosomes we're just not able to see using a light microscope electron micros scps are one of the newer technology microscopes we have they have much higher magnification and resolution ability than a light microscope this means we can see more structures that are smaller than with a light microscope and the reason is because the microscope has the ability to see separate objects clearly at high magnification which is what is meant by resolution they're really important in terms of our discoveries because we've been allowed therefore to see inside cells in way more detail and even inside subcellular structures like mitochondria and chloroplasts and even in the smallest of organisms like bacteria we've been able to see detail inside it's been an important development in understanding life on Earth you need to be able to explain and describe how to carry out a microscope practical where you can view structures on a microscope slide first of all we need to prepare the slide this example is going to be with onion cells so you would add a drop of water to a microscope slide you would take a very thin piece of tissue in this case onion skin it would need to be thin so the light can pass through it we then need to stain it in this case with iodine so that we can actually see the structures inside the cells like the nucleus in the cell wall then you would need to lower gently a cover slip on the top of your stained tissue to cover it before you put it on the microscope so when you go to put it on the microscope you would put it onto the stage so your microscope slide goes onto the stage of the microscope and it's held in place by stage Clips then you would need to rotate the objective lenses to the lowest power first this is normally about four times once you focused you can come back to the objective lenses to increase the power to magnify the image more at low Powers you use the cause Focus wheel to focus the image so that is no longer blurry at this point then you can go back to the objective lenses and rotate them in order to increase the magnifying power and then at high magnifications you're going to use the fine focus wheel to make your image focused at a higher magnification culturing microorganisms bacteria divide really rapidly by a process called binary fishing they can split into two as fast as every 20 minutes you can calculate this by using the following formula you take the number of bacteria that you start with and then you multiply by two to the power of the number of Divisions that have occurred bacteria can be grown in a liquid broth culture or on nutrient AAR which is like gel plates in order for them to grow successfully they must have enough nutrients and oxygen and also be warm so be at the right temperature and there should be no contaminants so there should be nothing else no other microorganisms that can grow there that could contaminate the sample so in order to prevent that the first thing we should do before using these is to sterilize the broth to the liquid medium or the AAR plate before you put any bacteria on it so to produce our uncontaminated plates we need to use the aseptic technique that you've seen in the video where you flame all your instruments that are metal or glass Flame the neck of any open bottles don't Place anything down onto the bench you should be holding it at all times once you need to put it down when you're finished you can put it into disinfectant you should disinfect surfaces and your hands before and after you carry out the Practical and you should always work near an open flame which produces a hot air flow and Carries any contaminants away from the where you're working on the Surface after you've made your plates for example if we're going to look at antibiotic resistance and have put some discs on top of some bacteria on a plate we need to incubate them at 25° so that we don't get any pathogenic bacteria growing you need to Loosely tape the lids shut to have a lid sealed on top but not completely sealed so the bacteria can still have oxygen in order to be able to grow the plate should also be placed upside down so that no condensation can fall on the bacteria once we've left our plates to grow for a few days we should observe the colony growth and look for any clear zones around our antibiotic discs you can then measure the diameter in two places normally at right angles to each other and then use a mean of these two values and P pi r s formula to calculate the area of the clear Zone around the dis larger clear zones around the dis will mean that more bacteria have been killed and so the antibiotic is better or stronger chromosomes DNA is a long molecule that forms a twisted double helix sections of DNA are called genes DNA is a really long molecule so it has to coil up and coil up and coil up to form solid structures called chromosomes to fit inside the nucleus inside the nucleus chromosomes are normally arranged in pairs you can see them here in humans there are 23 pairs of chromosomes in the nucleus of every cell in the body mitosis and a cell cycle the cell cycle is the process that all cells go through to prepare for cell division and then to divide and then it starts again as soon as they've divided the majority of the cell cycle is spent in interphase which is where the cell is preparing for division so it replicates its DNA so it doubles it it grows in size you can say the cell elongates and it increases the number of sub cellular structures so as well as doubling the DNA the numbers of things like ribosomes and mitochondria will also increase after interface the cell is ready to divide and that process is known as mitosis which is where actual one cell divides into two identical daughter cells firstly the chromosomes are pulled apart to opposite poles or ends of the cell the cell membrane and cytoplasm then divides this forms two genetically identical da cells that have the same chromosome number this process of cell division allows organisms to grow so from small organisms to large organisms as they grow older and also to replace cells in damaged tissues or organs stem cells stem cells are undifferentiated cells which can produce different cell types through the process of differentiation we've looked at these already before there are three different types of stem cells or sources stem cells that we have to know the first is embryonic stem cells these can differentiate into nearly any type of animal cell adult stem cells which can be found in bone marrow can differentiate into some type of animal cells for example blood cells but not all types of animal cells plant stem cells are found in the tips of roots and sheets these are known as meristems they can differentiate into any type of PL cell we mentioned before that plant stem cells can have this ability to differentiate throughout the whole of their life and this is how we can use it to clone plants this means we can make lots of plants really quickly and that's useful in some cases because we can save rare species from Extinction therapeutic cloning can be used to produce embryonic stem cells that are genetically identical to the patient these stem cells can now be used to grow new cells that can replace the damaged ones that the patient needs for example blood cells after maybe a cancer treatment to treat paralysis we can grow nerve cells or nerve tissue when that's been damaged in the spine for example or pancreatic cells to treat type 1 diabetes there are some ethical issues around using embryonic stem cells there is an objection to the fact that the embryo cannot consent to be used unlike if adob stem cells are taken from a patient that is able to consent and the concept of an embryo being potential life mean that unused embryos being destroyed is not accepted by some people there is also a risk of viral infection transfer especially if the stem cells are coming from another person or potentially a cancer because stem cells can divide rapidly so inputting dividing cells into the body could lead to a tumor diffusion is the net movement of particles from an area of high concentration to an area of low concentration so so net just means overall so the particles will move randomly in random directions but overall over time more particles will move from an area of high concentration to an area of low concentration this is a passive process because it does not require energy in terms of what's diffusing into and out of cells mostly oxygen and glucose will be diffusing into cells as these are needed for respiration so they get us up and will be in low concentration inside cells carbon dioxide and Ura diffuse out of cells these are waste products for metabolic processes so they will build up inside cells and be in higher concentration so they will diffuse out there are four factors that affect the rate of diffusion one is the concentration gradient if you increase the concentration gradient or difference in concentration then you increase the speed of diffusion if you reduce the distance that particles have to travel that increases the speed of diffusion mostly this is done by reducing the membranes needed to Cross or pass through in order to be able to get from one place to another increasing the temperature increases the rate of the movement of particles so that increases the speed of diffusion and increasing the surface a of the membrane that particles have to cross also increases the speed of diffusion there's more space for the to get across the membrane all exchange services will have adaptations to maximize the rate of diffusion so exchange services are places in organisms where majority of diffusion happens and these are why they have this adaptation they will all have thin walls a large surface area and good blood or Air Supply thin walls such as having one cell thick walls in the small intestine in the village helps to reduce the diffusion distance and therefore speed up diffusion a large surface area obviously we know increasing the surface area increases the rate of diffusion and a good blood or Air Supply is ordered to maintain a steep concentration gradient so constantly substances that are diffusing through are being moved along to create low concentration gradient behind them that means that diffusion keeps occurring in the right direction that we want it to happen there three specific exchange surface examples that we need to be able to explain and describe how they have these adaptations and how it makes them good at doing exchange so for example the alveoli in the lungs in humans this is where gases diffuse between the lungs and the blood capillaries the villy in the small intestine this is where small molecules so amino acids glucose fatty acids and glycerol which are the products of digestion diffused from the small intestine into the blood in capillaries and finally leaves implants this is where gases will be diffusing in and out of stomata and into the spongy nfil tissue layers where they will be exchanged with cells that are carrying out respiration and photosynthesis this is all linked to this idea of surface area to volume range shap which we need to be able to not only calculate but explain so surface area to volume ratio is where we divide the surface area of an organism by its volume and we've gone with cubes here to give you an example but the idea is that the larger the organism becomes the smaller their surface area to volume ratio becomes if you look at my cubes and if we think about diffusion the distance between the center of each Cube and then to the outside or to the external environment is much greater in the larger organism with the larger length of size of the que so compared to its volume the distance between its volume and all of its outer edges is longer this means diffusion from the very inside of that organism to the very outside of that organism would be very slow because the distance is very long so we can't just rely on substances diffusing from the outside into all of the cells in the body if we are a larger organism single celled organism like this example I've got here do not need an exchange surface like the ones we've just looked at because they have a very large surface area to volume ratio because it's a short distance between all of their internal sections to their external surface membrane so it's really quick for sub to diffuse from outside of the cell to the inside of the cell and therefore they don't need to have any adap to speed up that rate of diffusion however the larger an organism gets the smaller its surface area to volume ratio becomes so it needs these specially adapted exchange services like alvioli like villy and then a transport system like our circulat system in order to increase the rate of diffusion of substances into and out of every cell in the body so it can happen fast enough for processes like respiration and photosynthesis to occur osmosis is the net movement of water molecules from a dilute solution to a more concentrated solution through a semi Parable membrane it's really important when you're writing this definition in the exam that you say water molecules because it's only water that moves for osmosis and you get the dilute and concentrated the right way around and you don't forget to add the part of our semi membrane this could be a thre Mark definition so it's important to have all of that learned as part of your definition for osmosis when we say a semi peral membrane what we mean is a membrane that let small molecules through but not large ones for example a cell membrane you can get artificial per semi permal membranes as well and they can use those as an example in the exam so it's not always something that happens just through cells just like diffusion it's a passive process because it does not require energy water will move into or out of cells bi osmosis depending on the difference in concentration of the cytoplasm of the cell so inside the cell compared to any solutions outside of the cell just like diffusion it's affected by the same factors temperature surface area and concentration gradient if you increase the temperature or you increase the surface area or you increase the concentration gradient or difference then faster osmosis will occur there are three conditions and we have to know what would happen to animal and plant cells in each of these conditions cells that are in a dilute solution such as pure water water will move into cells by osmosis because there is more water outside of the cells than in the cytoplasm of the cell animal cells can swell and they can burst plant cells will swell up but they don't burst due to their cell wall stopping that from happening when cells are in a solution that has the same concentration as their cytoplasm there will be no net movement of water into or out of cells this means that no osmosis will occur cells remain in the same state in terms of how much water is inside their cells this is why it's important for things like blood plasma which is the solution surrounding red blood cells to have the same concentration as red blood cell cytoplasm when cells are placed in a more concentrated solution such as salt or sugar solution water will move out of the cells by osmosis animal cells can shrink and shrivel up in plant cells they don't shrink or shovel up as much because their cell wall is very strong and stays pretty much in its shape but the vacu will shrink and the cytoplasm can pull away from the cell wall in extreme circumstances now you'll notice in each of these I've used the same phrase about where water is moving to and from and I've used the phrase bi osmosis that is really important if you are answering an osmosis question in the exam you have to use the word osmosis when you're describing not only where the water moves from and to how it moves as in by osmosis we need to be able to explain how we can do practical methods in order to observe osmosis happening so this is an example and most of the examples you'll see where we use different concentrations of either salt or sugar solution and we put a piece of plant tissue into that solution this can be any plant tissue o potato red pepper carrot it doesn't matter matter what the tissue is as long as it's got plant cells because these cells will not shrivel or burst we want them to just change in terms of their mass and then we have to make sure that we keep all of our control variables correct to make sure that we're just observing what's happening to those cells as a result of being in different concentrations of the solution so in nearly every example of this practical your independent variable is the concentration of solution because that is what is being changed the dependent variable is the mass of tissue or the change in mass of tissue from before and after the experiment this makes sense because if cells gain water by osmosis they'll increase in mass and if they lose water by osmosis they will decrease in Mass there are many control variables in this experiment for example the volume of solution the time that the plant tissue spends in the solution should be the same for all the different concentrations the length and volume of the tissue pieces so how you cut them they should all be the same size but rather than saying size use the words length and volume because we're trying to make sure that they have the same surface area to volume ratio because that can affect the rate of Osmosis the same type of tissue should be used so from the same potato or from the same type of potato for an example so that there isn't differences between the cytoplasm of the cells there should be no skin on any pieces of tissue because skin is made up of a different type of cells and this can be water crew so this can affect osmosis the temperature of the solution should also be the same you can either do this experiment in a water bath to keep it the same temperature or at room temperature is fine remember control variables should be anything that could affect the results of the experiment and in this case it's anything that could affect the rate of Osmosis in each of these different solutions the the other key thing to remember is that when we are weighing and measuring the mass of the tissue after it has been in the solution we need to blot our pieces of tissues dry to remove any solution so that doesn't affect the mass I've got an example of a graph produced from dated from this experiment and always need to remember that when we are looking at graphs like this often they will ask you to show the concentration of the tissue how could you use this graph to work out what the concentration of the cytoplasm the cells in these pieces of part tissues is so if you plot percentage change in mass against the concentration gradient and then you look for where the line of best fit crosses the x axis which will be zero so at that point there is zero change in mass so we know that there's no water moving into or out of the cells therefore in this case the concentration that is closely closest to the cytoplasm of the cells in this example is 0.6 mole so this is how you would use these graphs it's always looking for where the line of es fit crosses the x-axis at zero where that means there is no change in mass because that must mean that the concentration of the solution and the concentration of the cytoplasmic cells is the same so there is no Osmos active transport is the movement of particles from low to high concentration against their concentration grading using energy this is not a passive process unlike osmosis and diffusion because it requires energy from respiration unlike osmosis and diffusion the rate of active transport is not going to be affected by the same factors it's mostly affected by the rate of respiration as the rate of respiration increases the rate of active transport increases this means that it can be affected by the number of mitochondria in a cell or the availability of oxygen if this isn't there or present then less active transport is going to be able to take place because there'll be less respiration happening it can also be affected by the number of caring proteins so the reason active transport requires energy is because we're using proteins in the cell membranes to actively change shape and move molecules from one side of the membrane to the other we need to know two examples of where active transport occurs in cells plants it's the root hair cells these transport mineral ions against their concentration gradient from the soil into the root heer the animal example can be found in the cells that are around the vly which line the small intestine these transport glucose molecules against their concentration gradient from the small intestine into the blood after equilibrium is reached both of these cells also carry out diffusion but having this ability to do active transport maximizes the absorption of these essential nutrients so plants cannot survive without mineral ions and in animals we need all the glucose we can get from our food in order to carry out respiration so once diffusion has happened and these molecules have tried to move into cells down their concentration gradient if there is still glucose left in the small intestine and if there's still mineral ions in the soil but there's a high concentration already inside the blood or inside these cells they will use active transport to make sure they get every single L mineral ion or molecu GRE perries to make sure that we absorb the maximum that we can the adaptation of these cells is that they will have lots of mitochondria to help provide the energy needed for lots of active transport any cell that you get told or is given as an example of a cell that carries out a lot of active transport will require a lot of mitochondria to provide enough energy through respiration to do that process [Music] [Music] [Music] [Music] we need to know how living organisms are organized so from the smallest part all the way up to the whole organism cells are the smallest living unit and the most basic building blocks of light a group of similar cells working together to carry out a function is known as a tissue a group of tissues working together to carry out a function is known as an organ then groups of organs come together to form organ systems multiple organ systems work together to form the whole organism so an example of a tissue is a palisade tissue layer in leaf which carries out photosynthesis an example of an organ is the heart which pumps blood around the body an example of an organized system of organs is the nervous system and then a whole organism would be something like a whole plant a whole insect or obviously a human and so we need to be able to understand that these go in size order as well so cells are the smaller then tissues then organs then organ systems then the whole organism here's the diagram of the labeled digestive system you should notely know this from keystage three and be able to L one of these exactly like this just like the salivary glands in the mouth secrete saliva that contains the enzyme amalay this digests carbohydrates so an example is starch which would be the substrate the enzyme is amalay and they react together and it breaks down starch into glucose which is smaller sugars the stomach contains hydrochloric acid to kill bacteria and secrete proteas enzymes to digest proteins so this is where we have proteins the proteas enzyme breaks these proteins down into the smaller molecules which is amino acids the small intestine is where the absorption of all the small molecules into the blood occurs it contains all three types of enzymes that are secreted by the pancreas including lipase to digest lipids so lipids are broken down by lipase enzymes into glycerol and fatty acids so on this page we need to be able to remember all of the enzymes what they break down what they break their substrate down into so the product or the small molecule we need to know where they are secreted from which I've written down here and where they work so in the salivary gland is where amalay is made and it works in the mouth proteas is made in the stomach and it works in the stomach and then the pancreas makes all three enzymes a form of amas proteases and lipase so it's made in the pancreas and but they work in the small intestine to complete digestion and that's then where all of those small molecules are absorbed when we're talking about enzymes and how they work we need to understand that they work through this idea of the lock and key mechanism where the substrate acts like a key and the active site of the enzyme acts like a lock it has a specific shape so that only one substrate can bind to the enzyme digestive enzymes are really important because they break down large insoluble molecules to small soluble molecules which can be absorbed through the cell membranes and into the blood to be transported and built into new molecules or for respiration in all the cells in the body amino acids The small molecules that are absorbed can be used to build proteins again for growth glucose can be used to build other carbohydrates like glycogen as an energy store or they can be used directly in respiration to release energy cells the fatty acids and glycerol can be used again to make lipids which can act as an energy store or they can act as insulation the rate of enzyme action or the rate of enzyme controlled reactions can affected by a few things one of them is temperature if you increase the temperature you'll increase the rate of reaction unless it gets too high and then the enzyme become denatured pH is also a factor that affects enzymes outside of the oct and pH for an enzyme it Cy nature and therefore slow down the rate and surface area of a substrate or the concentration of a substrate if you increase this it will increase the rate of reaction because there's more substrate and more surface area for the enzyme to bind to when we say denatured what we mean is the active site changes shape and therefore it can no longer bind to the substrate the last part of digestion we need to know is about bile bile is produced by the liver and it neutralizes stomach acid in the small intestine it also helps to digest fats through the process of emulsification so is made in the it is stored in an organ called the galbladder which then releases it into the small intestine which is where it works to help digest fats bile is not an enzyme increases the speed of digestion of lipids but it does not actually do the breaking down it is not an enzyme it just binds to large lipid droplets breaks them into smaller lipid droplets which increases the surface area so that the lipase enzyme can bind to Greater surface area and therefore break down the lipids into glycerol and fatty acids faster for all those molecules we've talked about during digestion we need to be able to show how we can identify these different molecules in food using various chemical tests the starch you would add iodine and if starch is present there will be a color change from yellow brown to blue black you must say blue black or you can say black in the exam but you cannot just say blue because this is the color of other test reagents for proteins you would add bioret reagent the color change if protein is present is from Blue to purple for glucose we would add benad reagent you must spell this with a capsu letter same as bioret because they are named after people and you must heat it up it will not work at room temperature you should say heat boil or specify it's over 80° if glucose is present they'll be a color change from light blue to Brick red the lipids you would add ethanol then add water and Shake to mix it together and a cloudy white Emulsion will fall a negative result for any of these tests would be no color change so stay in yellow brown for starch staying Light Blue for protein and glucose and there no Emulsion present for lipid there are many ways that you can measure the rate of an enzyme reaction and you can be given lots of different examples in the exam the independent variable could be pH or temp temperature or substrate concentration because changing all of these can affect the rate of an enzyme reaction depending on what the reaction is and what you're measuring it's going to change the dependent variable so you could measure a color change using an indicator so the time it takes for a color to change to indicate that a substrate has been used up you could measure the mass or volume of the product of an enzyme reaction you could measure a change in pH so for example when lipids break down they produce fatty acids so the pH will decrease as more fatty acids are produced over time so you can measure this with a pH meter there are also control variables for each experiment but similar ones will be things like volumes of solutions the concentrations of solutions and then pH or temperature whichever one you are not changing as your independent variable the example you may have looked at is starch and amalay in this example our independent variable is temperature and we could use a water bath to vary the temperature of the different reactions our control variables would be using the same concentration and volume of both the substrate and the enzyme and then we can measure the time that it takes for iodine to stop changing blue black to show that all the starch is digested so taking small samples of of the mixture solution every 30 seconds testing it with iodine until it no longer turns blue back to show that all of that starch has been digested by the amalay enzyme this is a graph of something predictable like a similar result that you might see where we've got the temperature on the x-axis and the rate of reaction on the y- axis we normally see this mountain shape where we can describe that as the temperature increases the rate of reaction increases due to the increased kinetic energy of the particles there's a Peak which is the optimum temperature and then after the peak the rate of reaction decreases as temperature increases because the enzyme is denatured you'll notice that most human body enzymes like the ones we've been looking at for digestion will have an Optimum temperature around the same as human body temperature which is about 37° C we need to know the three different types of blood vessels and how their structure relates to their function AR transport blood away from the heart at high pressure this is how I remember that a for arteries and a for away from the heart they have a narrow Lumen to maintain high blood pressure they have a thick elastic layer so they can stretch and recoil to maintain high pressure so the maintaining high pressure here is part of their function and this is how it relates the vular structure so if you're describing and explaining the structure and function of arteries need to talk about the so the narrow Lumin is a structure what does it do how does it help it carry out its function it helps to maintain high pressure lastly it has a thick muscle layer to withstand high pressure you need to use these words otherwise you won't get marks veins transport blood to the heart at low pressure they have a wider human to transport a greater volume of blood they have a thinner muscle and elastic wall layer because their blood is being transported at lower pressure so we do not need the same features we see in arteries veins have valves I remember this with the V for vein and the V for valves this is to prevent the backflow of blood due to gravity capillaries transport blood close to cells so that substances can be exchanged they have a very narrow Lumen to slow blood flow down to one blood cell at a time this increases the time for diffusion to occur they have thin walls that are only one cell thick to decrease the diffusion distance and ultimately they join small arteries and veins together so once exchange has happened the blood flows into veins and then can return back to the heart you need to be able to use all of this information to be able to compare the structure of the different blood vessels as well as their functions blood is a tissue which transports substances around the body and plays a role in the immune system the majority of blood is made up of blood plasma which is the liquid that blood cells are suspended in it's mostly water but it contains all the dissolved substances that are being transported around in the blood things like glucose and other things like antibodies for example and other dissolved substances from the digestive system like the amino acids and things that need to travel to and from your cells the rest of blood is made up of three different types of blood cells that are suspended in this liquid they're red blood cells white blood cells and platelets platelets are involved in clotting open w to try and prevent infection or to prevent excess bleeding red blood cells are specialized cells because they have no nucleus they contain lots of the hemoglobin protein which is the red colored protein that binds oxygen they have a biconcave shape which gives them a large surface area to increase diffusion of gases into and out of the cells and their job is to transport oxygen to and from cells there are two two types of white blood cells phagocytes these engulf pathogens and lymphocytes these produce antibodies or antitoxins both of these defend the body from pathogens and prevent you from getting sick so they play a part in the immune system we need to be able to label and describe the structure of the heart first of all with any heart diagram always write on the right and left the right way round so it is the opposite to how your hands are on the page then we won't get mix up with our rights and our lefts the two top Chambers are the atrium and the two bottom Chambers are ventrical think about it as a comes before V in the alphabet so a is at the top and V is at the bottom the blood vessel that brings deoxygenated blood from the body to the heart is the venara it is a vein once blood has entered the right atrium is going to flow down into the ventricle and the contraction of the right ventricle will push the blood up and out of the heart through the pulmonary artery it is an artery because it's taking blood away from the heart and it's taking blood to the lungs to be oxygenated when blood returns to the heart from the lungs it returns in the pulmonary vein so because it has been to the lungs it is now oxygenated blood this is the only vein in the the body that carries oxygenated blood the blood then moves through the left atrium which contracts and pushes it into the left ventricle which will contract and push it up and out of the aorta this is the biggest artery in the body and it takes blood at the highest pressure because it has to send it to the whole of the rest of the body the left ventricle has a thicker muscle wall this is so that it can contract with great Force so that blood is forced out through the a at higher pressure because it has to go a further distance to get around the whole body than when it leaves the pulmonary artery and just goes to the lungs the human circul system is known as a double system or a double pump system because the blood flows through the heart twice once to the lungs and once to the rest of the body so the right side sends blood the body to the lungs and the left side sends blood from the lungs to the rest of the body the heart rate is controlled by a group of cells known as the pacemaker cells that are found in the right atrium if these cells stop working they can cause arhythmia which is an irregular heartbeat and an artificial pacemaker can then be fitted to control and regulate the heartbeat the right hand side of the heart pumps blood to the lungs to be oxygenated and to remove carbon dioxide you can see a diagram of the lungs here we should know the trachea or the wind pipe branches out into two Brony and then the alvion at the end of the tiny branches which are known as bronchioles and we have two lungs one on either side here we've got a diagram of one alveolus from a bunch of alv and the capillary that's next door you can see both of the walls are only one celf thick as we mentioned as this is an adaptation we have deoxygenated blood coming from the heart on the left hand side when it reaches the alveolus then diffusion of carbon dioxide from the blood into the Alvi will happen and then oxygen will diffuse from the Alvi into the blood this is where it will bind to the red blood cells which will carry and transport it back to the heart once the oxygenated blood will arrive back at the heart then the left hand side of the heart will pump this to the rest of the body coronary heart disease the coronary arteries are blood vessels which transport blood to the heart muscle itself if these coronary arteries get blocked with a fatty buildup called plat then blood flow is reduced so less oxygen and glucose can reach the heart muscle without enough oxygen in glucose the heart muscle cannot respire so it stops Contracting this can cause a heart attack some risk factors for coronary heart disease that means they increase the risk or the chance of you getting coronary heart disease or poor diet and lack of exercise this is because they can lead to other conditions such as high blood pressure high cholesterol and obesity which are all medical risk factors for coronary heart disease we need to be able to describe some treatments for coronary heart disease statins are drugs that can be taken to lower cholesterol these are a preventative measure so they cannot reduce any buildup that is already there but they can reduce future buildup of plat or fat in the coronary arteries in the future stents are a metal meshlike cage which is used to widen arteries that have been narrowed by this fatty Builder this can help to increase blood flow with serious coronary heart disease it can cause heart failure if heart failure has been caused then the options for treat treatment are a heart transplant or a heart bypass or an artificial heart which can be used to keep someone alive until a transplant becomes available you need to be able to discuss the advantages and disadvantages of these different types of treatments for coronary heart disease health is a state of physical and mental well-being causes of ill health include disease which can be communicable disease or non-communicable disease communicable diseases are diseases that can be passed from one person to another and they are caused by a pathogen non-conical diseases cannot be passed from one person to another diet because this can lead to certain non-communicable diseases and stress which can be caused by social or lifestyle factors different types of diseases might interact with each other and you need to know how viruses can infect cells and cause cancer for example HPV can cause cervical cancer immune reactions to infections with a pathogen can trigger allergic reactions like skin rashes and Asthma so asthma is a form of allergy severe physical ill health caused by disease can lead to depression and other mental illnesses non-commutable diseases cannot spread between organisms they're not caused by pathogens they are usually longterm and get worse slowly examples include asthma diabetes and heart disease risk factors can increase the chance of getting these diseases non-communicable diseases can be caused by genes or genetic factors these are out of a person's control they could be caused by m a or they could be inherited from their parents the following are all risk factors related to Lifestyle and ofer choices alcohol has been linked to effect in unborn baby's brain development excessive alcohol consumption has also been linked to liver disease and brain damage a high fat diet can lead to obesity obesity is a risk factor for type two diabetes and a high diet can also lead to high cholesterol which is a risk factor for heart disease smoking whilst pregnant can reduce the birth weight of unborn babies smoking has been directly linked to causing lung cancer and lung diseases and it also increases the chance of heart disease ionizing radiation this is a link to your physics specification so a carcinogen that damages DNA in cells so it's an example of that exposure to ionizing radiation has been linked to cancer for example UV ray exposure has been linked to an increase in skin cancer so you've got this idea that ionizing radiation will damage DNA and then that can lead to it causing cancer which we're going to look at next but most diseases will be caused by a mixture of different factors coming together it's not always just one of these cancer is a non-communicable disease where uncontrollable cell division causes tumors to form there is some damage to the cell normally to the DNA this Alters the way the cell division process occurs this leads to uncontrolled or unlimited cell division which then forms a Chima some ch can be classed as benign these are slow growing and non-cancerous because they are contained in a membrane and do not spread to other parts of the body or other tissues malignant tumors though are cancerous they are fast growing and they can break off and spread to form secondary tumors in other parts of the body or other tissues while traveling through the bloodstream you need to be able to Define cancer as controllable cell division and know about the two different types of tumors risk factors for cancer smoking introduces carcinogenic chemicals into the body through the tar that's in the cigarettes and it can cause lung cancer but others as well exposure to UV radiation which we said is a form of ionizing radiation has been linked to skin cancer obesity is a risk factor because we know that fat cells can signal other cells to divide viral infection we've talked about the example with HPV that can cause cervical cancer some cancers can be caused by genetic factors so either mutations in DNA or inherited genes that can increase your chance of getting a certain cancer for example the braa gene which is known to increase your chance of getting breast cancer a leaf is a plant organ that is made up of different tissue layers one of the tissues in the zum this transports water and mineral ions the Palisade mfil is a tissue layer that contains cells that have lots of chloroplasts in order to absorb light for photosynthesis it's where the majority of photo syn this happens in a Le the upper epidermis is a transparent layer of tissue that lets light through to the palis layer for photosynthesis the spongy mphil tissue is an open tissue with lots of air spaces between the cells creating a large surface area for gases to diffuse and it's where the majority of gas exchange takes place the lower epidermis contains the staral pores that allow gases and water vapor to enter and exit the leap the flm is the tissue that transports sugars the guard cells are specialized cells in the layer of the lower epidermis they control the opening and closing of stomata they must balance the knes to open the pores for gas exchange with trying not to make sure that they're open too often or for too long to prevent too much water also being lost through transpiration through the pores The Roots stem and leaves form an organ system in plants which transport substances the main method of transporting is transpiration which is the flow of water from Roots to the leaves and is known as the transpiration stream the process of transpiration is where water vapor evaporates through the stomata the zylin is a tissue made of specialized cells that are adapted for the transport of water and mineral ions water flows up one way from the roots to the leaves through the transpiration stream through the zylin which is found in the roots the stem and the leaves they have thickened walls of ligin to help them cope with this transport function and their cells have no end walls between them which allows this continuous column of water flm is a tissue that contains specialized cells that are adapted for transporting the products of photosynthesis mostly sugars but also amino acids around the plant from the leaves to everywhere else in the plant that might need them this process is known as translocation the main adaptation of FL cells is that they are elongated and they have little holes or perforations in their end walls to allow substances to pass through freely transpiration is the evaporation of water vapor through the stata of leaves transpiration or the rate of transpiration can be measured using a Pomer so you can see the diagram set up below this is just an example different Pomers can look different but we need to understand that we have a plant sheet which will have leaves and Stat that the water can evaporate from and that is connected all the way with an unbroken column of water from the bottom of the stem through a capillary tube which has an air bubble in it that's the only air bubble though and we can move the air bubble to the start of the scale with the tap and the air bubble is next to a scale so we can measure the distance of the air bubble moves as water is sucked up through the plant shoot and we are relating the fact that if it's sucking up more water from the plant shoots at the bottom that is because more water is being lost at the leaves you need to be able to explain how different factors can affect the rate of transpiration air movement or wind if this is increased it will increase the rate of evaporation of water so therefore increase the transpiration rate light intensity if this is increased more stata will open so therefore this increases the transpiration rate temperature if this increases then the rate of apparation is increased humidity this is the only one that does the opposite and transpiration will decrease as humidity increases because it decreases the rate of evaporation [Music] [Music] [Music] [Music] can communicable diseases can spread from one organism to another because they are caused by pathogens that can be transferred pathogens are microorganisms that cause disease one example of a pathogen is a virus these are small a cellular which means they are not made of cells they live inside cells and replicate causing damage to the cell when they burst out they can reproduce rapidly inside humans another example of pathogen is bacteria these are procaryotic cells that can reproduce rapidly inside humans bacterial cells release toxins which cause damage to cells inside the body which is what gives you the symptoms and makes you feel sick another example of a pathogen is fungi these can grow on the surface of leaves or skin and they feed off living tissue and lastly protests these are single celled and often parasitic organisms that live inside and replicate inside host organisms which cause damage communicable diseases can be spread through the air through direct contact or through vectors an example of transmission by air is known as droplet infection this is where we inhale pathogens in particles from coughs and sneezes there are two forms of direct contact either by consuming contam minated food or water that contains the pathogen or by touching or having contact with infected tissue for example blood an example of contaminated food is salmonella which is a bacteria that causes food poisoning and an example of direct contact through infected tissue is HIV which can be transmitted through bodily fluids including blood an example of vector transmission is malaria so this is caused by a protest pathogen which is transmitted by a mosquito Vector when it bites humans there are three examples of viral diseases that we have to know the first one is Measles the symptoms of measles are kind of a red rash so spots on the skin and a high temperature or fever it spread through droplet infection because it also causes a cough and it can cause blindness and even death especially in children the only way to prevent the spread of viruses like measles is through vaccinating young children the next example is HIV this is a virus that infects and kills white blood cells it weakens the immune system and eventually leads to AIDS which is where a person has a weakened immune system and will get secondary infections such as pneumonia or colds or bacterial infections which can then kill them because their immune system is too weak to be able to fight them off this is transmitted through sexual contact or bodily fluid contact so one way of preventing the spread is by using condoms as a barrier method of contraception the tobacco mosaic virus is an example of a plant viral disease it infects plants and it destroys their chloroplast to the leaves this creates a mosaic pattern of discoloration on the leaves and reduces the plant growth due to lack of photosynthesis you can prevent the spread of the tobacco mosaic virus by burning the whole plant and disecting any tools or hands that have touched the plant and it can be spread by insect vectors such as aphid so killing those can also help prevent the spread there are two bacterial disease examples we need to know the first is gonorrhea which is a sexually transmitted infection so we can prevent the spread with condoms similar to HIV the symptoms caused are discharge from the genitals and pain when urinating and it can also cause a fever salmonella is the second example this causes food poisoning that we have already mentioned as it spread from eating contaminated food for example raw chicken the symptoms of sickness fever and diarrhea we can prevent the spread by washing our hands for and after touching raw meat and also cooking food to high enough temperatures to kill the bacteria in the UK chickens are also vaccinated against salmona to try and reduce the spread and make sure it's not present in eggs as well in both of these examples the symptoms are caused by toxins released from the bacteria treatment for any bacterial infection involves antibiotics these are drugs that kill bacteria in the body or stop them from replicating not all antibiotics will be able to kill all bacteria we now have an example that there are many resistant strains of goria in the UK specifically which cannot be treated with most antibiotics there is one fungal disease example that we need to know that infects plants and that is Rose black spot the symptoms are suggested of the name so black or purple spots on the leaves and the leaves can also turn yellow and fall off plants often suffer from lack of growth because of lack of photosynthesis due to these black spots and yellow areas meaning there's less chlorophyll it is spread through fungal spores that travel by wind wind or water mostly in Rain droplets they can also be spread on Gardener toes and hands as they work between plants one way of preventing the spread is to move an infected plant away from the others until it is treated and safe to move back close to them we can spray plants infected with rose black spot with fungicide in order to kill the pathogen we can also remove infected Le and burn them to kill the pathogen and its spores these two will both help to prevent the spread of Rose black spot to other plants there is only one example of protest disease that we have to know and that is malaria malaria is caused by a protist parasite that can live in both mosquitoes and humans so some of its life cycle is spent in both organisms and it can cause cycles of fever and it can be fatal ways to prevent the spread malaria include preventing yourself from being bitten this could mean using mosquito or insect repellent or mosquito Nets or we can prevent mosquitoes from breeding to reduce their numbers by covering standing water which is where they lay their eggs and their lar develop human defense systems humans have some non-specific defenses that try to prevent pathogens from entering the body the nose contains hairs and mucus to try and trap pathogens the trachea and Brony in the Airways contains cyia on the cells to move mucus which contains trapped pathogens to the nose and mouth to be removed from the body or to be swallowed the stomach contains hydrochloric acid to kill bacteria in food or swallowed mucus and the skin acts as a physical barrier to prevent the entry of pathogens everywhere where else specific defenses work inside the body in case pathogens do enter and they're normally carried out by white blood cells fagos sites detect and engulf pathogens and digest them with enzymes lymphocytes are triggered to divide by mitosis when they detect a foreign antigen they will form plasma cells which release antibodies that are specific to the antigen on that pathogen and they can also produce antitoxins that can bind and neutralize toxins released from bacteria vaccines contain a dead or weakened form of a pathogen so they will not infect the person but the antigens on the pathogen will bind and Trigger white blood cells to produce antibodies that comines to the specific antigen on the pathogen so you can see have my pathogen my antigen which is kind of the spiky protein on the outside and my purple antibodies which combined to that antigen the white blood cells will form memory B cells that will remember the antigen on the pathogen and will produce more antibodies faster next time they are reinfected in order to prevent illness this makes people immune to that pathogen so the first time you are infected with pathogen or an antigen from a vaccine we go through the primary immune response to make antibodies for the first time so not many antibodies are made and it happens slowly the second time you get infected with the same antigen so if you inhale it naturally for example through droplet infection we have What's called the secondary immune response so because you have memory cells they produce the antibodies faster and there's more of them and so we get that bigger peak in the graph that we can see here for the secondary immune response this prevents you from getting sick and gets rid of the pathogen from the body before it has a chance to make you ill and before you can pass it onto other people vaccinating large numbers of a population can prevent the spread of a disease because making people immune means they cannot be infected with the pathogen and so therefore cannot pass it on to other people this is known as herd immunity examples of painkillers include ibuprofen paracetamol morphine and Codine painkillers are taken to treat symptoms of diseases such as pain inflammation and lower temperatures caused by fever painkillers do not treat the cause of the disease because they do not affect pathogens examples of antibiotics include penicillin amoxicilin and tetracycline antibiotics are drugs that kill bacteria they treat the cause of the Disease by killing the pathogen antibiotics cannot and do not work on viruses because these replicate inside cells and bacteria live outside of cells so antibiotics cannot get into or work inside cells antibiotic resistance some bacteria in a population have the ability to survive treatment with an antibiotic these will survive and reproduce passing on the genes that allow them to survive to their offspring over time we get an increase in frequency of the resistant bacteria in a population until we have a whole population of bacteria that cannot be killed by that antibiotic this is an example of natural selection and therefore evolution of bacteria we need to be able to suggest ways to reduce antibiotic resistance we can reduce prescriptions of antibiotics for viral infections so prevent doctors from giving out antibiotics unnecessarily making sure that patients take the full course of antibiotics every time so they take all of the antibiotics they're given even if they start to feel better and reduce the use of antibiotics in farm animals originally drugs were extracted from plants and microorganisms there are three examples we have to know one is aspirin which is used as a panula and this was extracted from Willow Tree Bark digitalis this is a heart medication that's extracted from the Fox Glove plant and penicillin which is an antibiotic which comes from the penicillum mold which was discovered by Alexander Fleming new synthetic drugs made in the pharmaceutical industry can still have plant extracts as their base but they must be tested for three things toxicity efficacy and dosage toxicity is referring to whether or not it has serious side effects or is toxic to cells efficacy is whether or not the drug works to act in the way that we want it to and dosage is about how much drug needs to be taken for it to work whilst not having too many side effects you need to know the three stages of drug trials what happens in each and what they are testing for the first stage is carried out in the lab and is known as preclinical testing where we test the drugs on cells tissues and animals at this stage drugs are being tested for toxicity and efficacy in the second stage we move on to clinical trials which involve humans in clinical phase one we use healthy volunteers and low doses are used to check for side effects in clinical trial phase 2 we would use patients who are sick with whatever the drug is supposed to help with and then we are testing for efficacy and dosage drugs cannot proceed through these drug trial stages unless they pass the checkpoints so only if a drug is not toxic and found to work in the preclinical stages will it pass onto the clinical trials with humans and only if the drug passes the clinical phase one where it's shown to not have serious side effects in humans would it be given to patients because it is unfair to give or risk Patients health or making the worse by giving them a drug that could cause serious side effects or that does not work clinical trials should be at least blind clinical trials this is where we use a placebo or a fake drug as a comparison to show that the real drug is actually having the effect in blind clinical trials only the patients do not know if they are getting the real drug or the placebo in double blind clinical trials neither the patients or all the doctors know who is getting the placebo this is the best standard of clinical trial double blind clinical trials are important because they reduce the potential bias from the doctors it reduces the psychological effects for example the placebo effect where patients may just report feeling better because they think they are getting the real drug and it can show that the real drug is having an effect when compared to the placebo so so we know for sure it is the drug that is working and actually having a measurable effect on the illness monoclonal antibodies are produced from a single cloned cell they are all identical and will bind to only one specific antigen or protein first a mouse is injected with an antigen then Mouse lymphocytes in the spleen are stimulated to produce antibodies that will bind to this antigen human tumor cells which are rapidly dividing are combined with the lymphocytes to form hyoma cells the hria cells divide rapidly and produce the antibodies millions of the mon clonal antibodies can then be collected and purified monoclonal antibodies have many uses it can be used in diagnostic tests such as pregnancy testing where they will bind to the HCG hormone it can be used to test blood for the presence of hormones antigens on pathogens or other proteins they can be used to identify molecules in cells or tissues by binding to a fluorescent marker so you bind the fluorescent marker to the antibody and the antibody will be specific for a certain molecule you're looking for to see if it's present in a cell or a tissue and when it binds to it it will glow they can be used to treat cancer by delivering radioactive therapy drugs directly to cancer cells by binding only to cancer cell antigens this prevents the radioactive chemicals damaging the rest of the body these drugs work by preventing V ing cancer cells from dividing or killing them you do not need to know in detail how all of these examples work but any example question or method that involves monoclonal antibodies will involve them binding two antigens or proteins they will be specific so they will only be able to bind to that one antigen or protein that they are made for you can attach identifying molecules or drugs or chemicals to the other end of the antibody so that means that when it binds to what you're looking for you can have for example a glowing chemical or a radioactive drug or some other kind of chemical like a blue bead which is what's used in pregnancy testing attached to the antibody as well we need to be able to evaluate the use of monoclonal antibodies the pros are that they can be produced quickly they can bind to almost any substance they can help to quickly diagnose disease and can help to Target Cancer Treatments directly to cancer cells and reduce harm to the rest of the body the cons are that they are very expensive to produce they create more side effects than we first thought due to interactions in the body they're not able to be as widely used as we first hoped and they are time consuming to produce in the first instance there are also ethical objections to the use of monocon antibodies specifically the use of animals needed to produce them because it includes an operation to remove their spleen or cells from the spleen also there's issues with clinical trials where monoclonal antibodies have been tested on humans and have caused serious side effects plant diseases can be communicable and they can be caused by bacteria fungi viruses and also they could be infected with insects like a which feed on the FL these insects can also be vectors of other diseases as well plants can also be affected by deficiency diseases this is where a lack of a certain nutrients can affect growth there are two examples we need to know nitrates which are needed to make proteins for growth and magnesium which is needed to make chlorophyll without magnesium plants can suffer from chlorosis otherwise known as yellowing of the leaves whether the disease is caused by a pathogen or deficiency lack of light absorption can reduce photosynthesis which results in poor growth no sugars are produced so there is little energy and other molecules like proteins cannot be made so in both cases plants suffer from poor growth plant symptoms that can be identified can include stunted or malformed growth of Le leaves and stems spots on the leaves which we saw with rose black spot areas of Decay or rotting growth or discoloration to the leaves or stems this is what we also saw with the tobacco Mosaic Rus here's an example of a necrotic lesion in the bark of a tree where some of the tissue is rotting away there are some ways that we can identify plant diseases either by looking at pictures or using a gardening manual or website to compare pictures of your plant with plants on the Internet or in these manuals taking tissue samples to a laboratory to be tested or using home test kits that contain monoclonal antibodies which could identify certain pathogen antigens plants have certain types of defenses that can help to protect them physical defenses include cellulo cell walls a tough waxy cuticle on their leaves and bark which is layers of dead cells that around stems that can fall off chemical defenses include antibacterial chemicals which obviously can kill bacteria and poisons to deter herbales from eating them mechanical defenses include Thorns or hairs on their leaves to deter herb Wars leaves that can move when they are touched and mimickry to try and trick animals so mimicry is when an organism looks like another organism [Music] [Music] [Music] [Music] plants carry out fenses using light energy absorbed from chloroplasts in the plant cells carbon dioxide that they take in from the atmosphere as it diffuses through the stomata into leaves water that is absorbed by osmosis from the soil by root hair cells and that goes to the prosen to produce oxygen which is released into the atmosphere as it diffuses out of the leaves via the stamata and glucose which is then transported by the flow into all cells to be used by the plant photosynthesis is the chemical reaction that takes place in plant cells that uses light energy carbon dioxide and water to make sugars the symbol equation is carbon dioxide plus water light energy over the arrow Oxygen Plus glucose which symbol Ru is C6 h126 it's an endothermic reaction because it takes in light energy we need to know how plants use the glucose they produce from photosynthesis a lot of it is used up in respiration to release energy for processes in the cells some can either be converted to starch or used to produce lipids for storage some is used to produce cellulos in the cell walls some is combined with nitrates from the soil to produce amino acids these can then be used to make proteins through protein synthesis we need to know the factors that can affect the rate of photosynthesis as you increase light intensity it increases the rate of photosynthesis as you increase the carbon dioxide concentration it increases the of photosynthesis photosynthesis is an enzyme controlled reaction so increase in the temperature increases the rate of photosynthesis up until the optimum and then it decreases if it increases past that Optimum temperature the amount of chlorophyll in a leaf or in chloroplasts in plant cells if there's more chlorophyll then more light energy can be absorbed so the rate of phos synthesis can be increased we need to be able to explain what's going on on in rate of photosynthesis graphs with the different factors so for light intensity and carbon dioxide the graph looks the same there's an increase and then a flat line on the increase or the slope of the graph at a whatever is on the xaxis light intensity or carbon dioxide is the limiting factor because as it increases the rate increases when we get to the flat line at B another factor is limiting the rate for phot synthesis not what's on the x-axis so for example it could be temperature the rate of photosynthesis reaction with temperature on the x-axis looks very similar and can be explained in the same way as any enzyme rate of reaction graph initially there is a low increase in the rate of photosynthesis when temperatures are low because there is less kinetic energy of the particles then we get to the peak which is the optimum temperature and the fastest rate of photosynthesis and then the slope of the ground goes down because higher than the optimum temperature the rate decreases due to enzymes that control photosynthesis denaturing these factors could be changed in a lab when doing the photosynthesis practical or you could need to interpret how these factors might affect plants growing outside when measuring the rates of photosynthesis in the lab we can change various independent variables based around the factors that can affect the rate of pH synthesis we can change the light intensity by moving a light or a lamp closer or further away from our plant we should use a heat shield in order to make sure that only light intensity is being measured and not temperature different colors of light can affect the rate of photosynthesis as more red and more blue light are absorbed and green light is reflected by chloroplasts so we can use different color LED bulbs or colored filters in front of a white bowl we could use a water bath at different temperatures to create different temperature conditions for our plant or we could change the carbon dioxide concentration by using different masses of bicarbonate of soda or sodium hydrogen carbonate which we would dissolve in the water the plant is in this test tube will see come up this test tube and measure that in a certain amount of time to be able to calculate rate you could also use a gas syringe or a measuring cylinder to collect and measure the volume of oxygen produced in a set amount of time let's look an example method with light intensity being the independent variable the control variables will need to be anything other than light intensity that could affect the rate of photosynthesis so we need to keep the temperature the same the volume of water the pond we is in the same the carbon dioxide concentration so the mass of sodium hydrogen carbonate used the same and the color of light should be the same the type of pond weed used or the same Pond weed should also be kept the same I've placed a heat shield which is just a beaker of water in between the lamp and the pond weed so that the heat energy from the lamp is absorbed into that water and increases the temperature of that water but the light energy passes through to our plant this means that only light intensity is the factor that's changing and the temperature should not change with our pond weed you could also use an LED bulb which does not produce as much heat my independent variable then is my distance from the lamp as we move the bulb closer to our pond readed the light intensity will increase so we start far away we measure the amount of bubbles produced in a certain amount of time then we move the bulb closer we can use a ruler to measure the distance leave the pondweed to settle for a small amount of time at least 5 or 10 minutes so that the rate of focos syis has time to change if it's going to change then you measure the number of bubbles in a minute or how long time you're going to do again and then again you would repeat by moving the lamp closer again letting it settle and then measuring the number of bubbles in a set time again just be clear in the exam what you are measuring how you're going to measure it especially having to remember to measure it in a certain amount of time if we're going to calculate rate make sure you clear about what the independent variable is is what are you changing in the experiment and making sure that you understand that all the other control variables should be kept the same if they're going to affect the rate of photosynthesis we need to be able to demonstrate the inverse Square law as the distance from a lamp increases the light intensity decreases as the photons in the light have to spread out over a larger area so there is less light energy overall hitting the plot in the practical we are moving the distance of the lamp so we can show that light intensity is directly proportional to 1 / the distance squared or the inverse square of the distance so in the Practical we are not changing the light intensity directly we are moving the distance of the lamp but we can show how the link between the distance of the lamp and light intensity is a linear relationship so if we plot the line of one over the distance of the lamp squared against the rate of photosynthesis you can see that it's a straight line that goes through the origin which shows it is directly proportional the factors that affect the rate of photosynthesis can interact with each other and to optimize plant growth a balance must be found temperature and carbon dioxide concentration have very little effect on the rate or photosynthesis at low light intensities so only if it's a warm sunny day or there's a high light intensity does the changing of temperature in carbon dioxide actually have much of an effect on the rate you can see from these graph that increasing the temperature by 10° and increasing the carbon dioxide concentration has an effect by increasing the rate of reaction but only when light is not limiting from this graph where we actually have all three factors plotted together light intensity two temperatures and two different carbon dioxide concentrations carbon dioxide concentration actually has the greater effect on the rate than the temperature because you can see here that the 0.03% carbon dioxide lines are much lower than the 0.3% carbon dioxide concentration lines and the gap between the 15 and 25° is actually sh a lot smaller if Optimum conditions are maintained then photosynthesis will happen at a faster rate increasing the yield a greenhouse can be used to control these conditions and optimize them light intensity is increased with glass windows and extra lighting for cloudy days and in the winter red and blue LEDs could also be used as these wavelengths increase the rate of R synthesis the temperature is controlled with automatic itic Windows fans and heaters that maintain an Optimum temperature throughout the year carbon dioxide concentration in the air in the greenhouse can be pumped in from burners or engines or nearby factories so anything that is burning fossil fuels will be producing carbon dioxide that can then be bured into a greenhouse or from growing fungi which will release carbon dioxide when they respire it can also be controlled with automatic windows using carbon dioxide sensors although not direct factors that affect the rate of photosynthesis plants need enough water and mineral ions and need them to be kept at an Optimum so that they are not stressed any Growers using green houses like this must balance the cost of having all of these extra features so the carbon dioxide the heaters or anything electrical being used to control temperature and the ability to kind of automatically go from the windows and all of this is going to cost money so we need to make sure that they're going to get enough yield out of their plants to offset this cost and make a profit respiration is not breathing it's an exothermic chemical reaction that occurs inside every cell to release energy from sugars aerobic respiration happens in the mitochondria in every cell it uses oxygen to break down glucose and release energy the symbol equation is O2 plus C6 h126 and then it produces carbon dioxide and water we need to know the uses of the energy released from respiration in organisms is needed to carry out chemical reaction to build new molecules like proteins carbohydrates and lipids it's needed for active transport to move substances against their concentration gradient it's needed for movement specifically muscle contraction and also for keeping warm while maintaining certain body temperature a reminder that any cell that carries out a lot of these processes so active transport muscle contraction in muscle cells or building new molecules they will have lot of mitochondria as an adaptation to make sure they can carry out more respiration to release more energy for these processes anerobic respiration in animal cells takes place when there's little or no oxygen still breaks down glucose to release energy but a smaller amount of energy is released it happens in the cytoplasm of cells so I've put in a box all of the facts we need to know about aerobic so we can start to compare it to anerobic so it happens in a different Place anerobic does not require oxygen the products are different and the amount of energy released is different in anerobic respiration glucose does not break down completely but breaks down into lactic acid lactic acid is toxic if it builds up in cells so it's removed by the blood to the liver anerobic respiration usually occurs in muscle cells during high-intensity EX exercise when there isn't enough oxygen getting to them anerobic respiration in plant and yeast cells is slightly different although in both cells it still occurs in the cytoplasm don't forget that in plant cells they also have mitochondria so they can also carry out aerobic respiration as well it still breaks down glucose to release a small amount of energy but the products are different to anerobic respiration in animal cells and we call this process fermentation glucose breaks down to form carbon dioxide and ethanol we need to learn about yeast and its anerobic respiration because it's used in the food industry the products of carbon dioxide from the fermentation reaction is used to make bread rise and the product of the ethanol or the alcohol is used in the making of alcoholic drinks such as beer and one we need to be able to explain the body's response to exercise during exercise the body needs more energy from respiration this is to help muscles contract during exercise the breathing rate and the volume of breathing increase in order to increase the concentration of oxygen in the blood the heart rate also increases in order to pump more blood faster to muscle cells to deliver more oxygen and glucose when talking about this we need to use the word more a lot because your body always breathes and your heart always beats and you are always transporting oxygen and glucose around the body and your body does always need some energy but when we are doing exercise we need more energy because we're doing more muscle contraction so we need to increase our breathing rate to have more oxygen and we need to increase our heart rate to transport more blood faster to the cells so they can have more oxygen and glucose in order to carry out more respiration in muscle cells as well we have a store of glycogen which is broken down to release the glucose for respiration if you have belonged high-intensity exercise not enough oxygen can reach muscle cells eventually an anerobic respiration occurs in them and starts to produce lactic acid the glycogen is also used up in muscle cells and they become fatigued and stop Contracting properly the lactic acid produced by anerobic respiration in the muscle cells travels in the blood to the liver the buildup of lactic acid causes an oxygen debt the oxygen debt is the amount of oxygen needed to react with the lactic acid to remove it from cells in the liver the lactic acid is converted back to glucose needing more oxygen after intense exercise to clear the oxygen Deb is why we breathe heavily after exercise even when we've stopped metabolism is the sum of all the chemical reactions in the body these are all controlled by enzymes and they require energy from respiration respiration itself is also a metabolic reaction photosynthesis is a metabolic reaction and it produces glucose glucose molecules can then be build together to make gly oen starch or cellulose glucose can also then be combined with nitrate ions that plants get from the soil to build amino acids amino acids can be joined together to form proteins in protein synthesis excess proteins in the body can be converted to Ura for excretion in the liver glycerol and fatty acids can also be added together to build lipids all of these are examples of metabolic reactions because they synthesize new molecules or break molecules down I've highlighted in green photosynthesis the conversion of glucose to cellulose starch or the combining of the glucose and the Nitro Ires to make amino acids all of these processes only happen in plants ouch this is why in some videos I explain scratches [Music]