[Music] hi there everyone welcome back to the channel I'm the GCSE Science teacher in today's video we're going to be studying all the key content for paper one biology GCSE so if you do enjoy this video and you would like me to make one for chemistry and physics let me know in the comments section below give this video a big thumbs up and do share it with someone else they don't miss out especially as the exams are very very soon I hope you find this helpful thank you so much for your support and let's get started so cell structure and cell biology in general is one of the first topics so let's talk about it you need to know quite a few things so let's start off with the general structure and function of cells we have two categories of cells the first one being eukaryotic cells these have a true nucleus and DNA which is found often in chromosomes this includes plant cells and animal cells so plant cells have three distinct organal that you must recognize and know the first one being chloroplast which contain lots of chlorophyll for photosynthesis we also can say a permanent vacu which stores cell sap and the cell will which is made of cellulose and helps with structure and support the other common organel that are found in both plant and animal cells include the mitochondria which releases energy for respiration and this breaks down glucose cytoplasm which is a cellular space for reactions to occur cell membrane which controls what enters and exits the cell the ribosomes where protein synthesis occurs and the nucleus which contains the DNA found in chromosomes there are lots of specialized cells let's talk about the animal cells first so we have the nerve cell or the neurons which have an insulating fat sheath that speed up the nervous impulses they also have long branches to connect to other nervous system structures as well we have the muscle cells which contain lots of mitochondria for muscle contraction remember there's three types of muscle we've got smooth codiac and sceletal we have the sperm cell which contains an acrone which has digestive enzymes to help penetrate the egg cell membrane the nucleus is haid so half of the DNA that is there which obviously matches with the egg cell's DNA to fill form a fully functioning individual they also have lots of mitochondria for energy um to move the cell to the location where the egg is and also a tail speaking of gamt we also have the egg cell or the ovar which has lots of mitochondria which provides energy for growth of the cell especially after fertilization the cytoplasm contains lots of nutrients for the cell to grow and again the nucleus is haploid so contains half that genetic information it also has a cell membrane that changes so only one sperm can fertilize the egg at any one point another type of specialized animal cell includes ciliated epithelial cells which line the respiratory system and essentially waft mucus away from the Airways into the the esophagus to be swallowed and destroyed we have the red blood cells that are really important in contributing to our health and well-being as they transport oxygen around our body through having a protein called hemoglobin which oxygen binds to and there's lots of hemoglobin there because the red blood cell does not have a nucleus so there's lots of space for hemoglobin they have a biconcave shape to increase the surface area for gas exchange and a thin membrane for that gas exchange to occur at an increased rate as there is a short diffusion pathway remember there are other cells that are not specialized but also are not ukari they're actually considered procars and this is because they have free DNA and this includes things like bacteria remember bacteria can be pathogenic but also they can be beneficial to us and the key definitions or key Parts you need to be aware of are the fact that bacteria have a nucleo or free DNA within the cytoplasm and this is like a single Loop of DNA they also divided by binary fishion and when they do this they can also pass on extra Loops of DNA called plasmids which essentially code for antibiotic resistance genes and they also have fella which allow them to move specialized plant cells include the root hair cell which has a large surface area to absorb water and mineral ions from the soil remember water is absorbed through osmosis but mineral ions are often absorbed either through diffusion or active transport depending on the concentrations we have the zylin which is found in the stem and helps the movement of water throughout the plant it's made of lignin which essentially has thickened walls for structural support they have no top and bottom walls for allowing that continuous movement of water through a hollow tube that holot tube allows water to move in one direction from the roots and above the Flo is another type of plant cell and this contains companion cells that provide energy to transport dissolve sugars and amino acids throughout the plant in a two-way system the SI tubes specialize and essentially help the transportation but do not have a nucleus as well so these are some of the key facts you need to be aware of this is the next topic cell Transportation so what does it include it includes diffusion osmosis and active transport three different mechanisms in which different substances can move in and out of cells and is controlled by these processes diffusion is a passive process that is essentially defined as the net movement of particles from a high to low concentration down a concentration gradient and across a partially permeable membrane often substances that undergo diffusion include glucose and different gases like carbon dioxide and also oxygen osmosis there is a required practical un need be able to write a method for and interpret data but osmosis is defined as the net movement of water molecules from a high to low concentration of water molecules so from a dilute to concentrated solution this is also a passive process that occurs across a partially permeable membrane you can see some of the data from the required practical here and just as a key note this does not always happen in the case of using potatoes sometimes the exam board will give you a different plant tissue so don't get CAU up with that but essentially the data shows you if the plant tissue has gained in Mass the chain is positive however if the plant tissue has decreased in Mass the change will be negative where the plotted line crosses the x-axis on the horizontal line this tells you the solution of the concentration is equal to the concentration of dissolved substances in the cell the last type of mechanism is called active transport and this is an active process so it requires energy to move particles against their concentration gradient from a low to high concentration across a partially permeable membrane often you will be expected to know that this occurs in different cells such as plant cells like root hair cells to actively transport ions from the soil but also in the small intestine to uptake glucose the next topic is cell division so mitosis and meiosis are two types of cell division that occur in eukaryotic cells it's important to mention that meiosis is often more of a paper two topic however at this stage it's worth mentioning here as a comparative Point mitosis is a really important cell division process as it allows for new cells to be produced from old ones to replace the old damaged ones it also makes exact copies that are genetically identic and this helps with growth and repair so let's talk about the process of mitosis before the cell divides it grows and increases the number of organel such as mitochondria and ribosomes the DNA will replicate so there are two copies of each chromosome now within the cell the chromosomes will line up and each set of chromosomes are pulled apart so one is on either end of the cell the nucleus will divide and the cyop plasm and cell membrane will divide also this produces two genetically identical daughter cells let's talk about meiosis next so meiosis you need to be able to spell correctly and you also need to know the differences that are included so meiosis like I said is a cell division and it's used to create gametes these all are produced to be genetically different from one another to provide variation so when the gamt fuse the male and female gamits the sperm and egg they produce genetically individual individuals and that is very useful for the Improvement of evolution so the DNA is replicated so there are copies of each chromosome and there are two divisions in meiosis four gametes form unlike in mitosis where only two cells form remember gametes is a scientific word for sex cells each gamet contains a single set of chromosomes and therefore the gametes are considered haid unlike in mitosis where the cells are diploid they have the full con complement of chromosomes that are there all gametes like I said are genetically different from each other and the parent cell so DNA structure so DNA is a polymer it's made up of monomers or repeating subunits and it has the shape of a double helix and it is double Stranded the DNA molecule is made up of nucleotides which are made up of phosphates nitrogenous bases and deoxy ribos sugars deoxy ribos is a pentos sugar and the nitrogenous bases include A C T and G A is complimentary to T and C is complimentary to G they are held together by hydrogen bonds and this essentially is what we call base pairing you also need to know everyone who's doing gcsc biology the microscopy magnification object size and image size calculations this is in a triangle for you a way to remember is I am and you may be asked to convert from millimeters to micrometers and vice versa to do that you go and times the millimeters by a thousand to get into micrometers and divide to get the other way round you will also be expected to rearrange this equation so definitely make sure you have a note of these the microscope itself has lots of lenses first being the eyepiece lens which is a x 10 which you look down and the objective lenses which includeed time 4 time 40 and time 100 however there are other types of M microscopes called electron microscopes specifically sem and temm these are much more expensive but have a higher magnification and resolution compared to the light microscopes they are as I said more expensive but they do produce really clear strong images as well the light microscope is portable and less expensive it allows you to observe living specimens in true color but you can't see ribosomes so the higher magnification and resolution of an electron microscope is much more advantageous in this way however electron microscopes only allow you to observe dead specimens as electrons are fired through them and they only produce black and white images so color editing would be needed later on which can even add to the expense if you wanted to observe a sample under the microscope you would need to use a mounted needle to place a cover slip over the specimen after a very thin layer of the specimen has been applied to a glass slide be very careful to add a drop of stained such as iodine so you can view and observe the organal within and that M needle essentially is used to lower that cover slip to prevent air bubbles from forming as well are enzymes they're biological catalysts that are proteins and this means they increase the rate of reaction within the human body or in an organism enzymes are folded into complex 3D shapes and this essentially helps them to bind to specific substrates for the reaction to occur a substrate you can think of as a key and the enzyme like a lock there is only one key that will fit that lock and that lock space is called the active site if the active sight changes in shape the substrate will no longer bind and this is called the lock and key Theory there are some conditions that enzymes are very um sort of sensitive to and this includes temperatured pH and substrate concentration if there's optimal levels are altered in any way it can cause denaturing of an enzyme so the active site no longer is the correct shape for the substrate to bind you need to be aware of three different graphs when an enzyme's activity is altered due to the environment it's in the first is temperature as you can see we have a slow increased linear line a peak and then a decreased sharply this is the same for PHS as well the temperature pH need to be optimal levels because at one point there is an optimal level the enzyme activity is working as quickly as it can however if the enzyme's temperature or pH environment changes drastically it can cause a stop altogether in the activity of that enzyme because of denaturation however substrate concentration is slightly different as you can see on the graph there is a plateau and as the substrate concentration reaches that positive uh Peak that highest amount you can see that's the optimal number of substrates however anything further than that that is added that is just a wasted amount of substrates because there's a saturation Point there's only so many enzymes that will be able to react with a substrate in a given time frame so that's why you would need to increase the number of enzymes that are in this reaction if you wanted that saturation point to increase further some other things to be aware of as well include three different types of enzymes that you should be aware of their activity so for example starch is found in lots of plants and this is stored glucose starch is broken down by amalay into glucose we we also have protease which is an enzyme that breaks protein down into amino acids and we also have lipase which breaks down lipids into fatty acids and glycerol notice that each of the amalay proteas and lipase are all enzymes and end in the suffix a which is a good indicator in the exam if you're not sure lastly there is a required practical you should be aware of where amalay is used and we look at the activity and how pH can affect the activity using iodine to identify the starch that is present the next topic is photosynthesis and absolutely fundamental chemical reaction that allows for carbon dioxide and water to chemically combine to form glucose and oxygen you need to be aware of the word equation but also the balance symbol equation as well put Sixers in front of everything except for the glucose molecule which you should be able to identify glucose is stored in excess as starch imp plants and can be tested using iodine if you wanted to test for starch in leaves you could get a variegated leaf and use ethanol to remove any excess chlorophyll and stop any reactions by boiling the leaf as well iodine is used to test for the starch as it will turn blue or black in the Pres of starch so the variator leaf is useful because only parts of the leaf are green indicating that photosynthesis is happening here because there's chlorophyll present and can actually absorb the light energy needed for the reaction to occur as light energy is absorbed this is an endothermic reaction and essential key points that you should be aware of are limiting factors in this topic there are three limiting factor graphs that you should be able to identify including temperature carbon dioxide concentration and light intensity for example with light intensity and carbon dioxide concentration you can see the graphs are very similar they first start off with a linear line and then they Plateau What's Happening Here is there's an increase in light intensity or carbon dioxide concentration but as the optimal level is reached the rate of reaction Remains the Same and this is because something else is now limiting that reaction it could be in the case of light intensity graphs it could be carbon dioxide concentration or in the case of the carbon dioxide concentration it could be the light intensity so just alternate whichever one you're talking about lastly we have the temperature graph and as you can see there is a peak to this graph and then a trough in terms of the peak that's the optimal temperature that the end enzymes work best out for this reaction however as the temperature rises too over past the optimal level the enzymes denat and that is what is happening here so the reaction actually stops in terms of the glucose that is produced in photosynthesis you need to know the key um examples of where glucose is used in a plant so the first one is it's stored as starch and as I said you can test for starch using iodine cellulose is also used for um the cell walls and this is a new way of kind of chemically combining glucose to form that cellulose for cell walls and this provides the cell with structural support glucose can also be stored as lipids in seeds and also can be used directly for respiration and this releases lots of energy so the plant can grow also glucose can combine with nitrates in the soil to make amino acids and proteins for growth and repair the last part of this topic you need to be aware of respiration is another cellular process that happens in all living cells including plants remember photosynthesis only happens in Plants but respiration occurs in all living tissues it's an exothermic reaction which breaks down glucose to release energy or ATP and there are a few different types of respiration so let's talk about it aerobic respiration is with oxygen so glucose is broken down to produce carbon dioxide and water however there is a different version of respiration called anerobic respiration where there is less oxygen and this could lead to fermentation and yeast or respiration in muscles that are fatigued during physical activity that is vigorous so let's talk about fermentation first of all this is a process that is used to make beer and bread as ethanol and carbon dioxide are produced when glucose breaks down with a lack of oxygen ethanol is used to make the alcohol and the carbon dioxide is used to rise the bread however in the case of rigorous activity this is also where anerobic respiration can occur and this happens in the cytoplasm unlike in aerobic respiration where this occurs in mitochondria this is a much less efficient reaction and cannot be sustained for a long period of time as lactic acid will be produced and this can cause muscle fatigue the way lactic acid is removed by the body is by breathing oxygen in and breaking it down in the liver and this is essentially where we talk about response of exercise and how we respond to it so during exercise our breathing and heart rate will increase and with prolonged vigorous exercise glycogen stores will actually be broken down in the liver and muscle and essentially produce glucose and this can help us to keep that Supply demand that is needed by our working muscles in the case of higher combined students and triple students you'll need to know about oxygen debt and this is essentially the amount of oxygen that's required to remove the lactic acid and replace the body's reserves of oxygen you need to know the different types of white blood cells so let's talk about them the first one is called phagocytes and these are non-specific responses to the immune system so phagocytes will engulf any foreign substance any pathogen that could be problematic to us they will engulf not eat remember to use the word engulf and release enzymes to break down the pathogen and this is during a process called phagocytosis phagocytes communicate with another type of white blood cell called lymphocytes and these produce complimentary and specific antibodies that essentially help the fosite identify pathogen remember a pathogen is a microorganism that causes disease including fungi protests viruses and bacteria the lymphocytes also produce antitoxins which neutralize toxins produced by bacteria and therefore reduce their effects there are a few non-specific defense mechanisms that you need to be aware of one includes the skin which act as a physical barrier to stop pathogens entering also a chemical barrier includes the hydrochloric acid found in our stomach we also have fago sites which I mentioned earlier that engulf any type of pathogen and Destroy them and we have nose hairs and mucus which trap the pathogen and the nose hairs will trap the dust and particles that could irritate our respiratory system further there are a few different types of communicable diseases that you need to be aware of a communicable disease is a type of disease that can be spread from person to person or organism to organism so let's talk about these let's talk about fungal diseases so an example includes athletes foot which can present as itchy feet sore toes and a rash Rose black spot can be found in leaves and this essentially has spotted leaves which can stunt the growth the transmission Route for both is direct contact and also in terms of the Rose black spot in Plants this is infected gardening tools being shared prevention is to clean the infected gardening tools or isolate and destroy the inflected plants fungicides can be shared or used for athletes foot and to wash sweaty socks and change socks as well treatments for athletes for include antifungal medication but in terms of Rose black SP you would need to use a fungicide which kills any of the spores protest diseases include malaria and this can present as itchy spots from insect bites and a fever it can also lead to death the transmission Route includes bites from mosquitoes which is a vector or a micro an microorganism that is transported by an organism such as an insect prevention is antimalaria medication mosquito Nets mosquito repellent and to destroy the habitats by cleaning stagnant pools of water the treatment is antimalarial medication post infection a viral disease includes tobacco mosaic virus in plants which has yellow leaves stunted growth influenza is like the common cold and essentially causes muscle aches headaches and fever measles is a red rash causes fever and affects P primarily children transmission rout includes droplet infection for influenza and and also measles and direct contact infected gardening tools can be the transmission routee for TMV prevent prevention is to wash hands and to allow for vaccinations of measles in the case of TMV you'd want to kill and destroy any disease plants treatments for the symptoms include painkillers for for measles and influenza remember you cannot use antibiotics bacterial diseases can include goria which is a sexually transmitted disease and causes yellow green discharge from the genitals salmonella causes vomiting nausea and diarrhea the transmission Route can be sexual cont which is unpredicted so using a barrier method like condoms and also in case of salmonella is eating contaminated food or uncooked meat when preparing food prevention for cona includes condoms or different barrier methods and also to get regular STI and STD testing antibiotics can be used to treat the condition in the case of salmonella you want to wash your hands and cook meat thoroughly and origin of medicines come from plants and microorganisms examples include willow bark which is a form of aspirin or painkillers Fox gloves plants also produce a heart medication called digitalis drugs are tested in trial before patients can take them during clinical trials but also pre-clinical trials as well and this is tested to check the dosage toxicity and efficacy drug testing includes first looking at the drugs effect on computers and then cells and then animals such as mice then it goes to healthy Volunteers in the clinical trial stage and then to patients with the disease a placebo is used to see if the drugs effects are psychosomatic or if they actually have a positive effect on the person as well painkillers and antibiotics are two types of medication you need to know the information of so painkillers are medicines used to alleviate the painful symptoms of diseases such as aspirin and paracetamol which are often given painkillers do not cure disease but can be used on diseases that do not have a specific cure but do need treatment for pain such as influenza and measles remember toxins released by pathogens can cause us to feel ill so painkillers are often prescribed antibiotics however are only used for bacterial diseases such as gonorrhea and for salmonella mutations in the DNA of bacteria help them to evolve so the misuse of antibiotics is really important to know about so not finishing a course of medication giving antibiotics to diseases which are not caused by bacteria and overusing them in farming and agriculture can increase the like of antibiotic resistance amongst their different species and lead to um increased strains of bacteria that aren't able to be treated like MRSA remember antibiotics actually was discovered in 1928 by Alexander Fleming and he did make it clear that this was important to consider so antibiotics can't destroy viruses they can't be used to cure viral diseases or prevent diseases they are more of a cure however vaccines are used as a preventative measure to prevent against pathogens such as viruses and viral diseases and you do need to know what a vaccine is so it's an injectable substance that contains a dead or weakened form of the pathogen or virus and it triggers an immune response by getting the body to produce specific antibodies to the particular pathogen you need to be aware of the graph just to clarify an antibody is a protein that's produced by a white blood cell specifically the lymphocyte and an antigen is a protein found on the surface of the pathogen the antibody is complimentary in shape to the antigen on the pathogen the graph shows here the concentration of antibod is over time and in the first Primary Response less antibodies are made as it takes longer for the antibodies to be created but also for the different white blood cells and immune system to respond to the pathogen and identify it however in the second response there is a faster rate of antibody production due to memory cells which are able to differentiate and produce those antibodies that are needed so all more antibodies are made and stay in the blood longer and this happens at an increased rate blood is made up of four different components first of all the red blood cells which carry oxygen around the body by the protein hemoglobin white blood cells are part of the immune system to protect us against pathogens platelets help to form scabs and help the blood clot to prevent us bleeding and plasma is a liquid which contains dissolved substances such as carbon dioxide Ura and glucose the circulatory system in humans is considered a double circulatory system as it allows the blood to pass through the heart twice once to the lungs and once to the body the different blood vessels include capillaries veins and arteries that carry the blood suspension capillaries include very small vessels that connect arteries to veins and they have a very thin structure to allow for gas exchange to occur blood vessels such as veins have valves to prevent black flow and they carry blood under low pressure as they have less muscle and elastic tissue than arteries and have a slightly larger Lumen arteries however have a larger Lumen and thicker muscle and elastic tissue than veins do and they carry blood under very high pressure and they also carry the blood away from the heart the respiratory system is linked to the cardiovascular system because it works with the blood to allow for gas exchange the respiratory system includes the trachea and the Brony and the bronchol to then to the alvioli and alvioli is a very specialized area of the lungs which increases the surface area of the lungs and allows for gas exchange to occur gases that are breathed in such as oxygen are transported across the capillaries through diffusion and into the red blood cells and combined with the hemoglobin however carbon dioxide is carried in the plasma and this diffuses across into the alv and out as we exhale the small intestine is made of three different parts we have the duodenum the dagum and the ilium the duodenum will produce enzymes such as amas which breaks down starch into glucose protease or Trin which breaks down amino acids from protein and also lipad which break down lipids into fatty acids and glycerols the ilum also produces enzymes so amalay again but also another proteas called pepti days it's worth being aware of those adaptations of the small intestine allow it to absorb lots of glucose from the food that we consume and this is done through three key adaptations the small intestine has a large surface area thanks to the Villi and microvilli the Villi and microvilli are very thin in terms of their cell membrane and this allows for a short diffusion distance of glucose also the Villi and micro are connected to a wide vast network of capillaries that allow for glucose to be continuously absorbed by the blood and moved consistently around the body to allow for a diffusion uh gradient and consistent gradient so the uptake is increased there are some conditions called non-communicable diseases and these are diseases that cannot be spread from organism to organism an example is cancer which is defined as uncontrolled cell growth and division these can include different cells some of which are cancerous and some of which are not so the nine tumors are non-cancerous cells that are classified as abnormal and can later become malignant tumors or cancerous cells they are however contained in one area and have a membrane that encapsulates them they divide slowly and do not invade other parts of the body malignant cells which are cancerous actually do invade other parts of the body and they can spread to the other parts of the body by the blood or lymphatic system they can form secondary tumors and divide rapidly cancer risks include smoking UV exposure carcinogens and genetics and other ionizing forms of radiation such as gamma beta or Alpha radiation another type of non-communicable disease includes coronary heart disease so CHD and this is caused by an increased level of cholesterol in the diet for a prolonged period of time that actually leads to atherosclerosis or an increase in fatty deposits such as cholesterol in the artery that supplies blood to the heart and this is called the coronary artery this leads to a buildup of plaque and this stops blood from passing through the artery easily and therefore a blockage to can occur from the plaque and this essentially stops oxygen getting into the heart and can lead to a heart attack and death a way to treat this is by producing a diet which is lowering cholesterol and also increasing the activity of an individual Sten can be used to widen the artery to allow blockages to be removed we also can use St so plants can defend themselves from pathogens and you should know that there are three different types we've got physical defense mechanisms so thorns and sharp spikes to stop them being eaten by herbivores never say Predators we also have chemical defense mechanisms such as poisons that stop them being eaten we also have chemicals that help them protect from other pathogens like bacteria so these can actually be protective as opposed to destroying or killing any um different herbales that may eat them mechanical defense mechanisms also include certain structures that actually help prevent them being destroyed or weathered by the environment so bark protects the outside of the organism such as a tree from pathogen so they cannot enter and we also have waxy cuticles to leaves to protect them from weathering and other animals that want to consume them so we've already talked about the xylm and the flum and these are made up of a vascular Network called the vascular bundle that's often found in the stem and links the roots to the leaves it's important to mention that as well as this there are other structures that are found within the leaves so we have the E epidermis which is the top layer of the leaf and this contains the waxy cuticle that provides almost like a waterproof structure that stops the leaf from being damaged by the environment it also prevents water loss as well or transpiration there is a palisade layer that contains all the Palisade cells that have lots of chlorophyll to allow for the absorption of light and this is because it's near the top of the leaf so all that light can easily be absorbed through through the wax cuticle which is a transparent material the spongy mesil has lots of air spaces to allow gas exchange to occur when photosynthesis and respiration occurs and this essentially allows oxygen to go out of the plant and carbon dioxide to go into the plant in the case of photosynthesis the oxygen and carbon dioxide will diffuse through the spongy mesophile and the gases can diffuse out and into the plant through a structure called stomata which is a pore and opening and the opening of the plant's Leaf is controlled by guard cells that can swell to close it or become flaccid to open it and this depends on the temperature humidity and also the wind environment and this can also essentially control how much water is lost from the and that was a Whistle Stop tour of the entire paper one topics for GCSE biology I hope you found it useful if you did please let me know by sharing it and also giving it a big thumbs up you can also comment down below if there's anything you would like to learn more about in the meantime if you have listened to this video and you got to this point and you're thinking okay I need to revise a certain topic a bit more to learn more about it I have linked for you at the end of this video an entire playlist which contains all the cont content that I have shared with you on my channel but in one place so it's all paper one GCS biology so if you click on that it will take you to all the videos that I've talked about in the meantime I've been the gcsd science teacher and you have been curious thank you so much for your time and support take