hi everyone and welcome to miss estc biology and in this video I'm going to be going through everything you need to know for ciee topic 12 energy and respiration now if you do want even more help knowing the exact Theory key terms and examiner tip then don't forget to check out my a level notes that covers all of the theory and that is linked below for you so topic 12 let's get into it and it's covering energy and respiration so first of all all organisms require energy and that is for metabol processes such as active transport where you're moving substances across a membrane or other types of movement such as using ailia or fella or muscle contractions and also for building polymers so protein synthesis where amino acids are then converted and joined together to make proteins that requires energy as well as DNA replication joining together the DNA nucleotides and energy can't be created and it also can't be destroyed and instead said organisms use energy that is coming from bonds and the opposite of that is then making bonds to create molecules like polymers that requires energy but breaking them releases energy so photosynthesis is an example and this converts energy from the Sun into actually creating bonds whereas respiration this involves breaking bonds such as glucose which is the respiratory substrate used to ultimately create ATP and that ATP can then be hydrolized into ADP and pi and when that bond is broken between the inorganic phosphates that is what releases the small manageable amounts of energy which can be used in metabolic processes so let's take a closer look at the structure of ATP now it's known as a nucleotide derivative because it's got very similar components to a nucleotide it has this Pento sugar it has a nitrogenous base the key difference is instead of one inorganic phosphate group it has three inorganic phosphate groups and you need to know then that it is an immediate energy source for biological processes metabolic reactions in cells have to have a constant supply of this ATP so they have the energy for reactions and it's the bonds between these three inorganic phosphates which when they are broken the energy is released and that's used for chemical reactions within the cells so this structures then we briefly touched on it we said it contains a nitrogenous base in ATP that nitrogenous base is always adenine and nitrogenous means it contains nitrogen which we can see here inside of those Rings the pentos sugar is always ribos and then it has three inorganic phosphates so we can see here those bases or That Base adenine ribos and the three phosphate groups sometimes you might see it called adenosine triphosphate adenosine is the term for the adenine and ribos together so it's adenosine with three phosphates that's why it's a Denine triphosphate or ATP and the level of detail you need to know it in is actually here you don't need to know all of the atoms within it you just need to know that you have the nitrogenous base bonded to the pentos sugar which is ribos bonded to these three inorganic phosphates and the phosphate groups are described as being inorganic because they don't contain any carbon patters and for this reason in chemical reactions the symbol used to represent inorganic phosphate is p meaning inorganic phosphate so a bit more about ATP then and this time we've looked at the structure now we're going to look at the creation and hydrolysis of it so ATP is made during respiration from ADP which is a Denine D phosphate by the addition of an extra inorganic phosphates and that's a condensation reaction using the enzyme ATP synthes and that's what we can see here ADP plus pi that results in the production of ATP plus water and it's a condensation reaction so that's why we've got plus water water's been removed this is a reversible reaction ATP can be hydrolized back into ADP plus pi it's a hydrolysis reaction so water is added and with the help of the enzyme ATP hydrolase cataliz in this reaction it will then split or hydroly ATP into ADP plus pi and that's when energy is released when the bond between those inorganic phosphates is broken so this is done immediately you don't actually store ATP so that's why ATP is knowed as an immediate energy source you also get this energy very rapidly because you only have to hydrolize or break one bond to release that energy and as well as releasing energy to the surroundings ATP can actually transfer energy to other compounds CU if you adds that phosphate onto a different compound that compound will then gain the energy and that's what phosphorilation is it's when you add an inorganic phosphate group onto a molecule so it becomes more reactive or it gains energy so technically this is actually a phosphorilation reaction because ADP is gaining a phosphate group to become more reactive or to have more energy in the form of ATP and we'll also see this happening in the first stage of aerobic respiration because glucose get phosphorated as well so energy values of respiratory substrates near the start of this video I said that glucose is a respiratory substrate but you can actually use other carbohydrates and lipids and proteins if there aren't other carbohydrates available and all of these can provide energy to be used in respiration but they all have slightly different energy values per gram and that's due to the variations in the chemical structures and metabolic pathways and that's what I've got summarized here on this table so you might want to pause at this point and just cop this information so we've got carbohydrates lipids proteins glycogen or if it's in a plant it' be starch glycogen is only for animals and then alcohol so we've got the energy yield per gram so we can see you get the most energy from lipids then alcohol and then carbohydrates proteins glycogen starch are actually carbohydrates and this is referring more to sugars um you can see the metabolic pathways and then the conditions of use so that's a good one just to pause copy down or turn into flash cards if you want so the respiratory equation then or RQ of each respiratory substrate can be measured using a respirometer which is one of the Practical that you need to be familiar with and you divide the volume of carbon dioxide produced by the volume of oxygen used so that would be your formula the carbon dioxide produced divided by oxygen consumed and then you can use use that to compare different substrates as well so now we're going to move on to 12.2 which is respiration both arobic and anerobic respiration starting with aerobic respiration there are four key stages glycolysis the link reaction kreb cycle and oxidated phosphorilation you need to know where all four of those stages happen within the cell glycolysis happens in the cytoplasm but the other three stages all happen inside of the the mitochondria the link reaction and the CB cycle are within the mitochondrial Matrix which is shown in Blue on this diagram and it's the fluid Field Center oxidated phosphorilation the final stage happens on the Christi which is the name for this folded inner mitochondrial membrane shown in yellow so let's start with glycolysis and the first stage and this stage is where you are producing a small amount of ATP but you also use a small amount of ATP we said already it happens in the cytoplasm and this stage doesn't require any oxygen and therefore it occurs in both anerobic and aerobic respiration and there are three key steps that you need to know the first step is substrate level phosphorilation and this is when the glucose which is the respiratory substrate has two phosphate groups added to it from 2 ATP molecules and that makes it a far more reactive molecule and that's what happens in the next stage that phosphorilation once you've added those two phosphate groups to glucose it creates fructose 1 to six bis phosphate which is a six carbon compound still which is like glucose six carbon compound but because it's gained that energy from the joining or the bonding of those two phosphate groups it makes it unstable and therefore it splits immediately into two three carbon compounds known as trious phosphate or TP lastly then those TP molecules both of of them are oxidized and they're oxidized by removing a hydrogen and the reason removing a hydrogen is oxidation is a hydrogen atom is one proton and one electron so oxidation is the lot of electrons if you remove a hydrogen atom you are removing an electron so it's oxidized by the removal of a hydrogen atom and that will then form two pyruvate molecules now also in this oxidation we're going to create two reduced NAD NAD is a co-enzyme which is a molecule that can pick up and transfer hydrogen from one part of the reaction to another in respiration and we have NAD gaining the hydrogen that's been lost and therefore it's gained an electron and reduction is gain so you think of oil rig oxidation is loss reduction is gain so reduction is gain in an electron and if you pick up the hydrogen you are gaining an electron so you can call it nadh or reduced NAD and that stage stage three also releases four ATP molecules but that means we have a net gain of two ATP from glycolysis CU we had to use two at the start take that away from the four that are made we have a net gain of two so that's the stages written down let's have a look at it as a visual representation so it makes hopefully a bit more sense so we start off with glucose the six carbon compound we then have that substrate level phosphorilation stage where we said we're going to be using two ATP molecules to add on two phosphate groups so we phosphorated it to form fructose 1 to six this phosphate that is now very reative and unstable so it's split straight away into two molecules of trios phosphate that trios phosphate is then oxidized into to two molecules of pyruvate and it's oxidized by removing hydrogen which is picked up by NAD to form reduced NAD or nadh and in doing so two ATP molecules are created that happens on both of the trios phosphate molecules so overall the products we get from glycolysis are two three carbon compounds of Pates a net gain of 2 ATP so although we made four we had to use two and two reduced NAD or two nadh and the pyate and the reduced NAD are going to be used in the later stages of um aerobic respiration so here we have our glycolysis happened in the cytoplasm the next stages happen inside of the mitochondria and as we just said the pyruvate and the reduced NAD are going to be used in later stages so those now need to be transported into the mitochondria and they get get transported in by active transport into the mitochondrial Matrix the next stage then is the link reaction and this is when the pyruvate from glycolysis is oxidized to acetate we have another NAD which is going to pick up the hydrogen from this oxidation to create reduced NAD and that's what we can see here the pyruvate is oxidized into acetate and we know it's oxidation because we have made a reduced NAD or nadh which means a hydrogen must have been lost from pyate you actually also have decarbox which is the removal of a carbon in the form of carbon dioxide so that's where we go from a three carbon compound pyruvate to a two carbon compound acetate now acetate can enter the next stage which is the KB cycle without the help of co-enzyme a so acetate then combines with co-enzyme a to make acle COA or acle coenzyme a and that is the link reaction we don't have any ATP made in this stage but we do have acetal COA carbon dioxide and reduced NAD and I've written two times for all of these because although we only get one nadh one carbon dioxide and one aceto COA from the link reaction the link reaction happens twice for every glucose molecule because we had two pyate molecules made in glycolysis so the link reaction will happen twice for every glucose molecule so that's why we've said two times those products next then is the kreb cycle which is still happening in the same location which is the mitochondrial Matrix so here we can see the link reaction and that's going to lead us into the creb cycle and the first step of the creb cycle is oxyacetate which is a four carbon molecule is going to combine with the acetal COA and because we've got a four carbon reacting with a two carbon we get a six carbon molecule which is citrate and you do need to know the names of those compounds oxaloacetate and citrate at this point the co-enzyme a has served its purpose of helping the acetate react with the oxaloacetate and therefore it's released and it goes to be reused again in the link reaction we then have a series of Redux reactions there's actually lots of intermediates here but you don't need to know any of those intermediates you just need to know that there's a series of Redux reactions and that is because the carbon compounds are going to be oxidized and these co-enzymes are therefore going to be reduced they're picking up the hydrogen that's being released from the carbon compound so we end up making lots of reduced co-enzymes we have two carbon dioxides that are going to be lost and that's how we go from a six carbon back to a four carbon molecule and then we also have one molecule of ATP being produced at this stage so from one round of the KB cycle we get three reduced NAD one reduced fad which is another co-enzyme that picks up hydrogens one ATP and two carbon dioxides but much like like with the link reaction the CB cycle happens twice for every glucose molecule because we have two pyate made therefore two acetal COA therefore the cycle happens twice so for every glucose molecule we have six reduced NAD two reduced fad 2 ATP and four carbon dioxide molecules so this is just splitting up into those two stages the link reaction and the kreb cycle so summary so Far We've gone through glycolysis which happened in the um cytoplasm the pyruvate and the reduce NAD were actively transported into the mitochondrial Matrix which is where the link reaction and the KB cycle happened so so far if we total up what we have produced in terms of co-enzymes because those are what are vital for this final stage oxidated phosphorilation we have made in total 10 reduced NAD from one glucose molecule and two reduced fad from one glucose molecule and those reduced co-enzymes are really important for this final stage which is oxidative phosphorilation and this is where most ATP is created so involves an electron transfer chain involves the movement of protons the inner mitochondrial membrane or the Christi and we get ATP being produced by ATP synthes so let's go through what's happening then in the mitochondrial Matrix that's where we've just had the link reaction and the kreb cycle happening producing lots of those reduced co-enzymes those reduced coenzymes are now going to have the hydrogen removed which we can see here the hydrogen's been removed and that hydrogen splits into the protons and electrons and in this diagram the electrons are represented by these star-shaped Suns and the protons are shown here so the electrons are picked up by proteins embedded within the in a mitochondrial membrane and this is the electron transfer chain because the electrons then transfer along these protein as those electrons move from protein to protein they release energy and that energy is used to pump the protons from The Matrix through these proteins into the intermembrane space and therefore we end up with lots of those protons which are hydrogen ions all on one side of the membrane and it's in the inter membrane space which is the gap or the space between the inner membrane and the outer membrane so we get this electrochemical gradient which means we've got um a lot of a Charged molecule so that's what it's electrochemical gradient on one side of the membrane and that then results in the protons these hydrogen ions moving back across the membrane by facilitated diffusion down their concentration gradient and the only protein they can move through due to complimentary shapes fitting together is ATP synthes and as those protons move down their concentration gradient back into the mitochondrial Matrix through ATP synthes that then causes the catalyzation of ADP plus pi into ATP so as all of these protons move back down their electrochemical gradient that's how we get lots of ATP being produced now the final thing to be aware of is the role of oxygen here and oxygen is known as the final electron acceptor and that's because as these electrons move along the electron transfer chain or electron transport chain at the end of the chain if oxygen wasn't here to pick up those electrons then they would stay in that protein and therefore no more electrons can move along the chain and if you don't have electrons moving along the chain you don't have energy being released to pump the proton so you don't have an electrochemical gradient and therefore you don't get ATP being produced so it's really important that oxygen is this final electron acceptor meaning it picks up those electrons so the electron transfer chain can continue and we still get ATP being produced and that oxygen picks up the electrons it also picks up some of the protons and that is how water is produced in aerobic respiration so we then move on to anerobic respiration which is respiration in the absence of oxygen and it only occurs in the cytoplasm of the cell it involves only glycolysis from the stages we just saw and the pyruvate that's made in glycolysis in anerobic respiration it's reduced instead of oxidized and in plants and microbes it's reduced to form ethanol and carbon dioxide in animals it's reduced to form lactate or lactic acid and this is done by the pyruvate gaining the hydrogen from the reduced NAD that were made in glycolysis and the reason that needs to happen is that is going to oxidize the reduced NAD back into NAD and that means it can then be reused in glycolysis so you can still at least have glycolysis occurring to produce 2 ATP molecules so let's have a look at that represented visually we said glycolysis occurs so that's what we've already just gone through and then this time the pyruvate is reduced and we can tell it's reduction because that nadh becomes NAD which is the oxidized version and that hydrogen is picked up by and that would be two nadh here it's going to be picked up by one each by these py molecules and that is then going to reduce into lactate or lactic acid and that is actually toxic lactic acid is what causes muscle fatigue but it is worth making that toxic molecule so that the NAD is regenerated and glycolysis can still occur to make at least some ATP and anerobic respiration can't happen indefinitely because that lactic acid would Den nature enzymes involved in this stage and therefore it' then stop and that's where we get this oxygen debt we need to take in lots and lots of deep breaths to get enough oxygen to fuse it into the bloodstream and that oxygen can then break down the lactic acid in the liver back into non-harmful substances that can be used as respiratory substrates similar in plants and microbes but instead of making lactic acid or lactate we have ethanol and carbon dioxide being produced so in terms of the efficiency of these reactions one reduced NAD can result in a yield of three ATP molecules in that oxidated phosphorilation that we just saw whereas one reduced fad can result in a yield of 28 ATP molecules and if we think back to the fact that we said from one glucose molecule we create 10 reduced NAD and two reduced fad that results in 34 ATP molecules so we've got 3 * 10 and 2 * 2 so that's 34 but we also had a net gain of two in glycolysis and two produced in the creb cycle so that's why overall from one glucose molecule you get 38 ATP whereas from anerobic we only get a net gain of 2 ATP in glycolysis so there is a big difference there in how much ATP is produced in those two different reactions so you do need to know this example as well the rice plant adaptations because rice plants have evolved several adapt ations for growing in flooded or water log conditions so the arenta development which is a specialized tissue with air filled spaes in the roots and Stems this is to facilitate gas exchange so oxygen and carbon dioxide fusing in and out between the roots and the surrounding water it allows respiration when submerged by providing an oxygen Pathway to the root tissues and it reduces root weight aiding buoyancy in those water loged conditions so it will float you also have ethanol fermentation in the roots and that occurs under anerobic conditions in water log soils if there's limited oxygen and that provides an alternative metabolic pathway for ATP production that's is going to help the rise plants to survive even in very very low oxygen environments and then lastly we've got these resource allocations to the stems and the leaves that's prioritizing growth of aerial parts of the plant when it's submerged and that is going to maintain photosynthesis and overall growth despite the adverse root conditions and maximize exposure to sunlight and carbon dioxide for photosynthesis and carbohydrate production so collectively those adaptations enable rice plants to thrive in flooded or water logged environments facilitating rice cultivation in high rainfall regions or irrigated paty Fields so that is it for topic 12 I hope you found it helpful if you did look out for the later topics as well and check out my notes if you want even more support [Music]