Understanding Cell Respiration Processes

What's up everybody! So in this video we're gonna be talking about cell respiration. You guys have been asking for this video for so long. It only took me like four months to get it up. But the day came. We're finally here. You guys can have some faith in me again. Before we even start guys, go check out teachme.org if you want some awesome sexy looking notes and lots of IB style questions. Now back to the video. This video will be a long one. There's a lot of, a lot, a lot, a lot of things you guys gotta learn. But we put a lot of effort into this one. We got a lot of cool diagrams, a lot of nice ways to remember things. So I really hope this video will help you guys out. So sit back, relax and just absorb as much as you guys can. Put your brain cells together and let's get started. The first thing we're going to do is quickly look at the big picture before we can go into all these like nitty gritty details. OK, so what's what do I mean by big picture? So real quick, what's cell respiration again? And remember, it is basically the breakdown. of our food into a useful form called ATP because our cells money is ATP we need ATP to pay for all the things to happen in our cells okay glucose and fatty acids they're not useful okay they can't pay for all the things to happen but if we convert them by cell respiration into a useful form like ATP then that's what we need okay we need ATP to pay for everything to happen now a common misconception guys Is that cell respiration only applies to glucose? No, no, no, no Cell respiration is the process by which we turn our food that may happen to be glucose It could be fatty acids could be amino acids Anything like that cell respiration is the process by which we turn any of our food into with a series of reactions into ATP, okay, so it's not limited to glucose only but that being said for this video We're gonna focus on the process for glucose only Okay, we're gonna focus on the whole thing glucose goes through because glucose is the most important molecule that we care about With regards to making ATP, okay in cell respiration, so make sure to know and not get confused with that So what are we looking at here in a big broad sense? We're looking at the process here that glucose goes through in cell respiration We have our mitochondria here right outside of mitochondria is our cytoplasm So we're basically nice and zoomed into a piece of the cell here with some mitochondria and some cytoplasm And we can see there's a lot of steps that go on. So the four steps are glycolysis, link reaction, Krebs cycles, electron transport chain, and chemiosmosis. This whole aspect here, okay, requires oxygen. So that's going to be part of aerobic respiration, okay? Pyruvate, when there is no oxygen, okay? When there's oxygen, it will do all of these things called aerobic respiration. When there's no oxygen... anaerobic respiration is going to happen okay and we'll look at that later in this video on a separate slide okay so this is the big picture okay we're going to go into all of these steps in detail all the way from glycolysis to electron transport chain and chemiosmosis okay so just remember this big picture and we're going to come back to this now before we go into the actual individual steps we need to talk about oxidation and reduction i know you guys hate this always because it's so chemistry like but trust me It's not that bad. There's only a little bit, a very low level that we need to understand about reduction oxidation. A few things you got to memorize because we don't need to know the chemistry details. We're only biology, right? There's only biology. Don't need to know the teeny tiny things we cannot see. OK, so we're going to quickly go into this and then we're going to go into the details here of cell respiration. OK, so what exactly is reduction oxidation? Basically, these are two kinds of reactions. Let me show you here with a little the little molecules. So here we got two molecules, the blue one and the green one. Notice the blue one is basically stealing these electrons and hydrogens from this green one, then taking it for themselves. The green one lost it and now is without the hydrogen and the electrons. Okay, now the molecule that takes hydrogen and electrons from other molecules, we call that process reduction. Okay, so reduction is the process by which a molecule gains hydrogens and electrons. Oxidation is the opposite. Okay, so these guys, this green molecule lost hydrogens and electrons to become naked. So that's oxidation. Okay, so you can see that oxidation and reduction, they always happen together. You can't have one without the other. You can think of it like the scene from Tintin, where the thief steals wallets from other people. You can't have a thief without a victim. Okay, very important. The same thing here, you can't have oxidation without reduction. They always happen together. which is why they give the scientists give it a name called redox reduction and oxidation now Here's a little key table you guys need to know. It can come up for multiple choice questions or even long answer questions So pay attention to this. So as a quick summary Reduction is the gain of electrons or gain of high electrons or hydrogens Oxidation is the opposite loss of electrons loss of hydrogen Then another way of defining reduction is loss of oxygen and oxidation is gain of oxygen I wouldn't worry too much about this last one. I have it here if you guys want to remember it It's not too important for now. We may come back to it later in this video But the very key ones that you need need need to remember right now is this for oxidation and reduction Um, okay. Now here's a way to remember it. You guys have probably seen it. Your teachers probably mentioned oil rig to you guys Oxidation is loss of electrons and hydrogens reduction is gain of electrons and hydrogens So that's the big idea. See it's not too much Just remember these things because it's going to come up and up again throughout this video I'm going to mention these words a lot So keep this in your brains and you'll see we're going to reuse it throughout this video So it will get engraved in there. Trust me. So now We are gonna now we finished the big picture and redox. Okay, these are the two painful parts we had to finish now We're gonna go into the real stuff you guys want to learn about right? So first um, we gotta look at the equation of Um cell respiration this guys you probably have seen this right glucose. Sometimes you see it in equation form like this Sometimes you see it in word form Don't worry about it. We're gonna look at this now and we're gonna look at it again at the end of this video And it will make hopefully it will make much more sense at the end of this video So you can see it's glucose plus oxygen will yield or form carbon dioxide water And of course our atp right now ain't gonna make sense But just take a look at it absorb a little bit and we're gonna come back to it And you're gonna see that it makes a lot of sense. So now let's get into our glycolysis the first step here Okay, the first step here. So where are we first? Where are we? We're here, this is the mitochondria and outside we have what? We have our cytoplasm. Okay, so glycolysis happens in the cytoplasm. That's super important to understand. Now glycolysis literally means splitting, lysis means splitting, of glucose or splitting of sugar. So you can imagine what's going to happen in this step, right, in glycolysis. So let's start here, up here. Here we have our glucose, right? That's the thing we're going to turn into ATP. So that's our initial starting point. Now You may be like why is it in a chain like this? I thought glucose looked a lot like this. You're right glucose is actually in this shape right? It's a structure like this. It's got one, two, three, four, five, six carbons, some hydrogen, some oxygens. This is actually how glucose looks like but for the sake of explanation of this whole cell respiration process we're going to make it in a linear form okay? It's how they use it in textbooks. It's easier to understand and that's how they want you to remember it but do bear in mind that glucose actually has this shape. not a linear structure, okay? Just for explanation purposes. So the first thing that happens is glucose is going to react with ATP, and that's crazy. So we're using ATP in the very first step of cell respiration. I thought we're trying to form ATP. Isn't this defeating the purpose? You're right. It's crazy, right? But it's going to make sense. You'll see later in this video. So we do need to use ATP for the first step. Why? Remember, ATP is called adenosine triphosphate, so it's a molecule. with three phosphates. Now each ATP is going to add one phosphate group to this glucose. So you can see we have two ATPs which means we're going to add two phosphate groups to this glucose. So we're ultimately basically forming this. Okay we're forming a molecule that has two phosphates added. Okay and in the process of adding these phosphates these ATPs get converted into ADP because ADP is adenosine diphosphate. Di meaning two phosphates. So each ATP dropped off one phosphate to form ADP. So now, okay, that's kind of strange. So now we have this molecule here with two phosphates added. Okay, so what was this process called of adding these phosphates to glucose? It's called phosphorylation. Okay, phosphorylation. So remember this, phosphorylation, adding a phosphate. Okay, that's the very first step. So now we have this molecule called fructose 1,6-biphosphate. Okay. There's very few names you guys are gonna have to remember for the whole cell respiration process and this is one of them Okay, unfortunately, you may need to remember this name, but i'm going to help you try and explain why it makes sense Look, what does this 1 6 deal with? Look, this is the first carbon and this is the sixth carbon or you can think of it as this is the first carbon And this is the sixth carbon. So on the first and the sixth carbon we have a phosphate. Okay So that's kind of why there's a 1 and a 6 there. Okay, why is it called bisphosphate and not biphosphate? Why is the S there? Okay, when we use biphosphate, that means that the phosphates are on adjacent carbons. But we can see that these phosphates are not on adjacent carbons. This phosphate on the first carbon and the other phosphate is on a carbon very, very far away. In that scenario, we say bisphosphate instead of biphosphate. If the phosphate, if the two phosphates were on adjacent carbons, we'd call it biphosphate. So that's why this whole thing is called fructose 1,6-biphosphate. You don't need to know why it's called that, but just try and... hopefully that can help you remember this name a little bit better. Okay, so that's our first step. Now, these phosphates... By adding these phosphates, this molecule is very unstable. So phosphates make a molecule relatively unstable. Basically, it makes it want to react. So this molecule is not stable and now it's going to react. What's it going to do? Guess what? It's going to split. It's gonna undergo splitting lysis. So that's where this lysis comes from. So finally this molecule is gonna split in two Look now we have two molecules that are identical three carbon molecule with a phosphate attached. We call these triose phosphate Okay, because they got three carbon so triose because ose remember means sugar So this is a sugar triose and it's got a phosphate now. So that's lysis. Okay phosphorylation Lysis now each of these triphosphates will undergo now a bunch of steps So i'm only going to show it here for this one. But but bear in mind the same thing happens for this side Okay. Ah look here now now your oxidation reduction knowledge will have to come together Look at this molecule. You can think of it like a guy called nad. Okay nad this molecule is super super interesting It loves to take things from other people. It's like a thief Okay, so it's a lot like this scenario here. Let me go back to it's like this thief guy. It loves to take things Now, what is it like to take? It likes to take, let me show you, hydrogens and electrons. Look, this guy, NAD positive. It's going to try and take hydrogens and electrons from this triose phosphate. Okay. And in the process of doing that, it becomes NADH. See, now it's got a hydrogen and it's got some electrons. So we call it NADH. Okay. Hmm. So what do we call that again? I must, I must emphasize on this. So what's the process called when, say, so this molecule loses triose phosphate. loses hydrogens and electrons to this guy here. So when the molecule loses hydrogens and electrons, what happened? We call that oxidation. So this guy, when it loses its electrons and hydrogens, we call that oxidation. So guess what? This whole process we call oxidation and reduction. Because remember, reduction, I mean oxidation, never happens without reduction. How does that make sense? Remember, triose phosphate lost the hydrogens and electrons, so it was oxidized. But something else gained the hydrogens and electrons. This NAD+, right? It gained the hydrogen and electron, so it was reduced. So we can say that triose phosphate was oxidized and this NAD was reduced to form NADH. Okay, very very important. So step one, phosphorylation, lysis, now oxidation and reduction. Now you may be like, okay great, what the heck was the point of forming this NADH? Think of this NADH like a ticket, an arcade ticket. This is gonna help you a lot. It helped me a lot. Okay, you know in arcades when you play games and you win all these tickets They're kind of useless. There's a piece of paper But if you win enough of them, you can trade them in for a big gift Okay at the at the counter, right you can if maybe if you have a hundred of them You can get a big prize or something, right? So think of these NADH is like an arcade ticket We're gonna try and build up a lot of these NADH throughout this whole cell respiration process because at the end of the day We're gonna use these NADHs, these RK tickets and trade them in for a lot of ATP, okay? So that's what I want you to think about these NADHs as. They're like a little RK ticket. Very very cool. Okay, so other than that oxidation reduction, we also add a phosphate here, okay? So now we form a molecule here that is three carbons with two phosphates because we just added a phosphate, okay? This is different from this scenario here because this phosphate here came from ATP, okay? This phosphate is free-floating. It's called inorganic phosphate. When a phosphate is free floating, not attached to any other molecule, it's kind of just by itself like a loner, we call it an inorganic phosphate. Don't worry, I'll reveal all the words here later, okay? So this inorganic phosphate is now going to attach, so now we have these molecules, okay? Three carbons and two phosphates, okay? Awesome. Now, finally, the last step of glycolysis is this. So now we have ADP that are going to take these, that's going to take these phosphates off. So One ADP will come and take a phosphate to form ATP, then another ADP will come and take the other phosphate to form ATP, ultimately resulting in a molecule that has no phosphates and it's just three carbons, which we call pyruvate. Okay, so what do we call this little step here? ATP formation. Okay, because we formed some ATP. Okay, awesome. Remember the same thing happened on this side. Okay, so now now I want to tell you what this big brain trip was for. Look, if you want the one great way to remember the order of this is thinking of this people love outdoor activities. And this is how I used to teach it. But now, because nowadays things change, we're going to call it online activities. People love to be inside. So why the hell not just call it online? Okay, so it's you can remember if you maybe you're an outdoor person. You can call it people love outdoor activities, but you can also remember it as people love online activities. Okay phosphorylation p l lysis oxidation atp formation this is important because i've seen Some multiple choice question where they ask you to to arrange the order of these of these steps Okay, so you should know the order. Okay, so that was it for glycolysis. I want to look at the ultimate summary What did we really make in glycolysis? We made two atps. Do you agree with that? No You should be like no right because we made two atps here and two atps here. So shouldn't that be four? That's a good way to think about it. But remember although we formed four atps We spent two atps so four minus two is two so we only actually Net the net amount of atp was two. Okay, because we made four and lost two So we actually only made two and then we made two nadhs right one here and one on this side And then we made two pi rubates right one here one there. Okay, so that's very cool So here is the steps written out as promised everything I said this is all the important stuff you need to know So now let's go on to the next stage here next stage So coming back to our original diagram, remember i'm gonna now fill it in as we go along So we had glucose we underwent glycolysis by a bunch of steps, right? People love online activities to form pyruvate two of them right two pyruvates and in the process we made some stuff some atp But we made these tickets two nadhs these tickets that later We want to trade in at the last stage here for ATP. So these tickets, these NADHs are really important to remember about them. Okay, awesome. So now, good. We finished now glycolysis. Let's go to the link reaction. Okay, so here we are. Where the heck are we now? Okay, now we're looking. Okay, I want to make this clear. We're basically zooming in. Okay. You can see this picture. We're basically zooming into the matrix area with a little bit of membrane Okay, remember for the mitochondria this outer layer is called the outer mitochondrial membrane And then this inner membrane that bends and curves like this is called the inner mitochondrial membrane and then this space right outside Okay, the space in between the outer mitochondrial membrane and the inner mitochondrial membrane that's called the inter membrane space Okay inter membrane space. So right now we're kind of looking at the matrix and a bit of the the membrane okay, the inner mitochondrial membrane. You'll see why. Okay, so what's going on with the link reaction? So remember we just made pyruvate in the cytoplasm outside of the cell, right? Going back to it. We made pyruvate here in the cytoplasm, in the cytoplasm outside of the mitochondria. So now our pyruvate is going to be pumped into the mitochondria from the cytoplasm using some active transport, okay? So pumping it into the matrix. We got to pump it into the matrix now. Now, so now we have a pyruvate brought all the way from the cytoplasm of the cell into the matrix, okay? Now, what is the link reaction exactly do? So we have a three carbon molecule, the pyruvate, and remember, remember this, okay? I don't want to confuse you guys here. Remember we formed two pyruvates. So what I'm explaining now with the link reaction is gonna happen for both pyruvates, okay? So I'm gonna show it with one pyruvate, but remember It's happening with the other side as well, okay? It's not just happening with one pyruvate, so remember that. Okay, so what happens with the pyruvate? Okay, couple things. First, we got our little ticket man. NAD plus is gonna take more electrons and hydrogen to form NADH. What do we call that again? Oxidation and reduction. The pyruvate is oxidized because it loses electrons and hydrogen, and the NADH is reduced because it gains hydrogen and electrons. Okay, so that's gonna be our little ticket guy. We'll put the words here for you guys. So oxidation and reduction is gonna happen again. Now also, this 3-carbon pyruvate is gonna lose a carbon, okay, to form a molecule called acetyl. Acetyl. Okay, it loses this carbon in the form of carbon dioxide. Carbon dioxide. Okay, so I'm gonna put a carbon dioxide here. Because this carbon isn't lost just as a carbon. It comes off in the form of carbon dioxide. Okay, so remember that. And that... is already helpful here because look one of our products of cell respiration is carbon dioxide so you can see where this carbon dioxide comes from okay Okay, so that's cool. So we underwent oxidation and reduction. We lost a carbon. What do we call that process when we lose a carbon as carbon dioxide? We call it decarboxylation, okay? Because we have this carbon dioxide that comes off in the form, this carbon that comes off in the form of carbon dioxide. So that's called decarboxylation. Now, the last thing that happens is we have this little molecule called coenzyme A that's going to add on, okay? So you can see the final product we formed. Therefore... is acetyl CoA because we have this two carbon molecule called acetyl plus this coenzyme A. So we call it acetyl CoA. Okay? I want to emphasize right now while I'm thinking about it, remember when I talk about all these steps like glucose turning into this and this doing that, what is catalyzing these reactions? Do they happen magically by themselves? No, right? Remember each step has their own unique enzyme. Remember an enzyme is a little molecule, a little tool that catalyzes and makes things happen like a hammer or like a screwdriver. It's a little thing that makes a specific reaction happen and each step will have their own unique enzyme. I'm not showing it here but remember that. No reactions just spontaneously happen, they normally use an enzyme right? So it's the same thing here, there will be an enzyme here catalyzing this reaction. But you guys don't need to worry about the name of that enzyme or anything like that. Okay, give me a sec. So what did we form in the link reaction? Okay, two carbon oxides. You might be like why I thought we only formed one No, we formed two because remember there are two pyruvates. I'm showing you one pyruvate But when we break down one glucose we form two pyruvates each pyruvate will undergo a link reaction So we'll actually form two carbon oxides for one glucose molecule, right and same here two NADHs Okay, not just one because there's another pyruvate same here two acetyl coase. Okay, so you can see already I just want to show you this From the glycolysis, the products were 2, 2 and 2. Okay, it's the same thing here. Okay, 2, 2 and 2. Okay, so let's write now the words of what you need to know. Okay, here's the words for you guys. Make sure I don't screw anything up here. I don't know why. Give me a second, guys. I don't know what happened here. I don't think that should be there. Okay. That's it for you guys. So where are we now? So we have now, our glucose underwent glycolysis to form two pyruvates. Each pyruvate went into the matrix of the mitochondria where we underwent the link reaction to form acetyl-CoA. In the process, we made some of those tickets, right? Two NADHs that will, again, these guys will be traded in later for ATP. All right. So where are we at now? We did glycolysis. We did the link reaction. Now we're getting to the Krebs cycle. Okay, the Krebs cycle. So the Krebs cycle is a hell of a thing, guys. You guys will look at it and be like, oh, I don't want to do this anymore. But trust me, it's not that bad, guys. Come on. So remember now we did the link reaction, right? I'm going to re-show you it here just for clarity's sake. We got our pyruvate. Remember, it got pumped into the matrix of the mitochondria where it underwent what? The link reaction to form what? Acetyl-CoA. Okay, I didn't show the other things made because we're just recapping it here. Now, now this acetyl-CoA is going to enter what we call the Krebs cycle. Okay, the Krebs cycle. I cannot for the life of me think of a nice way to remember that the Krebs cycle is part of cell respiration. If you guys can write it in the comments, I'd love to know it because a lot of the times students get confused because they don't remember if the Krebs cycle is part of photosynthesis or part of cell respiration. But I can think of a nice way to remember it. If you guys can, please let me know. But another way. To call the Krebs cycle is the citric cycle or the citric acid cycle. Okay. Now you can think of this Krebs cycle as a little analogy. Okay. I'll kind of give you an analogy like a little Ferris wheel. So you got this, this people, um, four people. Okay. A four carbon molecule, which we call oxaloacetate. Four carbon. You guys need to know that name. Any, every time I put the name, you actually need to know it. Okay. So make sure you know this name. There's this four carbon molecule. Okay. There's four people on this, on this, on this, uh, Ferris wheel box. Okay. and they come down and now these two people or this acetyl-CoA is going to try and join these people so now we have six people on this ferrous wheel box okay so that's what happens this acetyl-CoA combines with oxaloacetate to form a six carbon molecule which we call citrate again please remember this name you need to know it okay you need to know both of these the other ones you don't need to know but oxaloacetate and citrate you need to know now as this acetyl-CoA combines with oxaloacetate this This coenzyme A comes off. As you can see, it's not here. It's not in the 6-carbon molecule. So it gets recycled. Okay, it gets recycled So that now this coenzyme is free again to combine with the next pyruvate so that another acetyl-CoA can be made Okay So this CoA molecule is really only useful to be able to combine with to combine this These two carbons with these four carbons after that it's it's not needed so it gets recycled So that's that's important to understand now this six carbon molecule something's gonna happen. Okay, two things again oxidation and reduction because guess what this NAD plus is going to take what? Electrons and hydrogens for itself to form NADH, this arcade ticket, right? So that's what we call that again. That means this, if these electrons and hydrogens were taken from the six carbon molecule, that was oxidation. And this NAD plus was turned into NADH, we call that reduction. Okay? So that's oxidation and reduction happened here again. And guess what? The six carbon molecule gets turned into a five carbon molecule. Okay? Because the six carbon one carbon comes off as a carbon dioxide. Okay, what do we call that again? Decarboxylation don't worry. I'm going to put the words very soon So you guys can think of this as a little like story So these four people join these two people now, there's six people the one person gets sick on the ferrous wheel, right? He's like, oh, I can't do this no more and he and he hates it that much he jumps off So now we have five people left. Okay. Now now this ferrous wheel box only has five people now this five carbon molecule again It's gonna go undergo oxidation, okay? It's gonna lose electrons and hydrogens to this NAD+. Okay, so the five carbon molecule was oxidized and this NAD plus was reduced. So we got more of these tickets. You can see these tickets, these arcade tickets are building up. Now, surprise surprise, another person gets sick and they jump off the, uh, they jump off, okay? So we have another decarboxylation, another carbon comes off as carbon dioxide, remember? So Another person jumps off now. We have four people left on this on this ferrous wheel. Okay now what? Very very similar pattern guys you guys will see so now we have again this oxidation and reduction to form NADH Okay, but now we have this other cool thing. There's another molecule Wait, let me take a sip of this coffee. My throat's going very dry. Okay Now we have another molecule that's very similar to NAD plus It's called FAD+. Now this molecule, just like NAD+, likes to take electrons and hydrogens from other molecules. Okay, so as it does so, it forms FADH2. Okay, and you can think of this guy as like a broken arcade ticket. So when this guy goes and returns or tries to trade in the NADH arcade ticket, he's gonna get a lot of ATP. Okay, because it's a good, it's a fresh ticket, but this FADH2 It's gonna the guy at the counter is gonna be like, but your ticket's a bit broken So I'm not gonna give you that nice of a price because your tickets a bit broken So that's what I want you to remember FADH2 is like a broken ticket. It's not as valuable as NADH Later on to get ATP. Okay, so it's still a ticket but it's not as valuable. It's like a broken ticket now very important What's unique about this this stage here is we're actually making ATP So you can see an ADP here is gonna come in and take a phosphate Which we didn't show here but taking a phosphate to make ATP. Okay, so in this step here, we actually have ATP formation Okay, very very good So now guess what we did after all these steps we regenerated this oxaloacetate Okay So now we're back to this four carbon molecule Now it can combine again with an acetyl CoA and the cycle can repeat and we can keep building up a lot of NADHs So I want to quickly stress something remember from the enzyme video This would be a cyclic metabolic reaction. Remember you have linear metabolic reactions and you have cyclic metabolic reactions This would be a cyclic one because it's a cycle you regenerate this molecule as you go around. Okay, let's put some words So what happened really here? We have ATP formation. Remember here we have how many d carboxylations? Two, okay. Let me put it here. Where where do we have it? We have one Decarboxylation here turning six carbon into five carbon and then we have another one here turning five carbon into four carbon But then we stay at four carbon. So we don't have another decarboxylation. We only have two so it's again It's two and then how many oxidations and reductions do we have? Let me move this a bit guys. Sorry We have four. Okay. Sorry high tech here. Okay four Because we got one here, one oxidation reduction, another one here, that's two, and then we have one. that's oxidation reduction but it's FAD and then we have one another one that's NAD so in total we have four oxidation and reduction reactions in one Krebs cycle. Okay so from Krebs cycle what's our final products? How many how many NADHs do we have? You can count here one two three but why did I put six because we have this Krebs cycle happens twice right because we have two pyruvates so we showed one pyruvate getting turned into acetyl CoA so we showed you one Krebs cycle but remember we have another pyruvate that's also going to do this. So Krebs cycle for one glucose molecule, the Krebs cycle will technically make six NADHs, not three. Okay, same. So we double everything. So we have four carbon oxides, not two, because it happens twice, and we have two ATPs, not one. Okay, so that's important. So hopefully that idea makes sense. Let me show you now the word form of that. So you can remember the analogy, it's going to help you, the four carbons. Four people join the two people you have six people one gets sick jump off Another one gets six jump off and now we're back to four and it stays four Okay, but what I can tell you for sure is at every single step at every single step we have oxidation and reduction oxidation and reduction this here we have oxidation reduction here We have oxidation reduction here. We have two oxidation and reduction But only in the last step do we have atp formation not in the first two so you can look at that Hopefully it helps you out But here's the word summary of all the steps you guys really gotta know. Okay, so let me show you here now our diagram again. So what did we do so far? We did our glycolysis, got a bunch of products including our tickets, link reaction got the tickets, and remember Krebs cycle we got six NADHs and two NADH2s which is the broken ticket. So we got a lot of these tickets and they're all now heading to this last step here of the electron transport chain and chemiosmosis where we're going to form all the ATP. Because you guys can see so far how much ATP did we really make basically nothing, right? Like we made one here in the maybe two in the krebs cycle for two krebs cycles we made Um, not we made nothing in the link reaction and we made only two in glycolysis So we basically made no ATP. So all the ATP must be made in this last step, right? So here I just want to show you a quick summary. This is actually to test you guys so here I have glycolysis the link reaction and the krebs cycle I want you guys to Put the number of each of these things formed to see if you remember well test yourself Okay, these things these little details are very easily quizzed upon in multiple choice. Okay, they love to do it So make sure you know it i'll show it to you guys So here you are It's very easy to remember for the first two because it's two two and two for this one It's two two and two just for the last one. It's more like two four six Okay, there's like a bunch of mix there so you guys can try and remember that. Okay? So guys, where are we now? We finished glycolysis, we finished the link reaction, we finished the Krebs cycle, and we're now going into the etc. No, we're going into the electron transport chain and chemiosmosis, okay? That's the last little bit here so we can finally see where all that ATP is coming from, guys. So where does this last step happen? Where is the electron transport chain and where does chemiosmosis happen? Well, look at our mitochondria. It happens in the mitochondria, but specifically, it happens... I want to move this for you guys. It happens there, right here, at this area here, the inner mitochondrial membrane, the outer mitochondrial membrane, and this inner mitochondrial membrane space. So this one doesn't really happen primarily in the matrix, it happens there. So you can see here from this diagram, I tried to label it for you guys, this membrane here is our inner membrane, so that's our inner membrane here, then we got this big space in between the inner membrane and the outer membrane, so it's the outer membrane, we call that the intermembrane space. and then outside of that we have the cytoplasm of our cell and then inside here we have the matrix the inner side of our mitochondria so we know the link reaction and the krebs cycle was happening here in the matrix so now we're going to come here to this little membrane area okay so what's going on here do you remember that we built up all of this like let me come back to it all of this nadh and fadhs all these rk tickets they're going to become really really really important here Okay in the electron transport chain, let me show you so here we have it we have our nad dhs Okay, we're first going to talk about those remember they are carrying all of these hydrogens and electrons, right? So they now they come to this inner membrane and what they do is they come to these little guys here What do we call these guys here? These guys are electron carriers this one this one this one this one this one this last one is not and we're gonna get to What that one is? But basically these first three, I mean these these first batch here these guys Is our electron transport chain electron transport chain and what they do is exactly what the name says They transport electrons. We're gonna see how so these individual guys they're called electron carriers Okay, so all of these electron carriers form our electron transport chain and in this last guy here is called our ATP ace And it's gonna be responsible for chemiosmosis. Okay, we'll see how what that is later So anyways, remember we had all of our little tickets, right? Our NADHs, they were built up and all that. So they're all accumulating now here in the matrix. So what they do is they now go to this inner membrane and they decide, you know what, I'm tired of carrying all these electrons and hydrogens. I'm going to drop them off. And he basically drops off these electrons to these electron transport chain. And also it drops off the hydrogens. OK, so it drops off the hydrogens. So here we have some hydrogens. and it drops off its electrons. Now the electrons, okay look look look at this, the electrons when they're dropped off this electron transport chain, all of these electron carriers are gonna basically play game of hot potato. So this one gets the two electrons and it's gonna pass it to the next one. It's gonna be like I don't want it, I'm gonna pass it to the next one. That one don't want it, it's gonna pass it to the next one. That one don't want it, pass the next one. So this is an electron transport chain because they're transferring the electrons that were dropped off by this NADH. Okay. Now these electrons, they're high energy, okay? They're high energy. Electrons are high energy. So what they do is, as soon as this NADH drops off these electrons, okay, this is going to activate this-these electron carriers to pump hydrogen across. Because remember, remember this, the NADH not only dropped off electrons, but also hydrogen, okay? But it drops them off here. The hydrogen is in the matrix. So there's no way the hydrogen can just go through unless it's pumped through by this electron carrier. So what stimulates that- pumping it's these electrons they're high energy so as they pass through these electron transport chains they stimulate these pumps to pump hydrogen into this inter membrane space this teeny tiny little space okay teeny tiny little space and this is actually interesting you can see how this inner membrane folds so much the reason why it folds so much is to increase the surface area so that so that this process can happen everywhere so we can pump as much hydrogens into this inter membrane space as possible because if there wasn't that much folding there wouldn't be that much area for this whole process to happen so all this folding is creating a very large surface area for this to happen a lot so we can pump in a lot of hydrogens so anyways yeah these electrons pump come in they cause these electron transport chains to pump in the hydrogen okay and not only this one it's gonna get eventually get passed down the electron transport chain and cause this one to also pump in hydrogen and this one to also pump in hydrogen right Okay, so basically pumping in a lot of hydrogen. Okay, a lot of hydrogen a lot of protons, right? We call these protons So when a hydrogen has no electrons because remember this NADH here it was carrying electrons and hydrogens So when the when this hydrogen has no electrons because the electrons went here we call it a proton So you'll see the word proton. So proton is a hydrogen with no electron. Okay, it's called a proton So now these protons are being pumped into this inter membrane space Now look, so that keeps happening. Now where the heck is the FADH? The FADH is interesting because it doesn't actually come So early. It doesn't start, it doesn't go to the first electron carrier. It goes later. Okay, so it comes more here So you can see here instead of instead of sending its electrons to the first electron carrier It sends it to the second one which means the electrons from this FADH2 Is not gonna stimulate this first one. It's only gonna stimulate the second one. So that means that this FADH It's only gonna activate these two guys to pump hydrogens So the FADH is gonna cause less hydrogen pumping than the NADH did because remember the NADH is sending electrons That will cause this one to pump hydrogens this one to pump hydrogens and this one but the FADH is only sending electrons here So it's only gonna activate this one and this one so less hydrogens will be pumped into the intermembrane space for the FADH2. That's why we consider it like a broken ticket. And you'll see why we call it broken ticket. Okay, give me a second. So same thing here. Okay, same thing here. Now finally, when these electrons reach the end, okay, they reach this last electron carrier, they need to eventually be accepted because otherwise where do they go? Okay. They need to be accepted by someone. So guess what accepts this electron? Oxygen. Look, we have an oxygen here. Okay, this oxygen is going to accept these electrons at this last electron carrier in addition to all of these In addition to two protons because remember these NADHs they kind of let go of these protons So in this matrix, we have a few protons eventually A lot of them are pumped into this inter membrane space, but there are still some remaining Now this oxygen will accept these electrons in addition to two hydrogens to form guess what water because water is H2O two hydrogens and oxygen Okay, so you can think of oxygen as the final electron acceptor because it's going to accept these two electrons along with Two protons to form water. Guess what coming back to our picture here. We got our water. That's where water is formed So we see now where all the carbon dioxide is formed and we see where the water is formed. Okay, give me a sec Okay Of course hydrogen is still pumped. Okay, so what we're doing, what we did now, all of these arcade tickets, basically what they did is they caused a lot of protons to be pumped into this intermembrane space. So it's building up and building up and building up and becoming super super concentrated. So we have a huge proton gradient. We have a lot more protons in the intermembrane space than we do in the matrix. So there's a there's a gradient. So these protons want to diffuse down, want to diffuse back to even out that concentration gradient. Okay, but they can't go through any of these guys. They need to go through a specific kind of transporter that we call ATP synthase. Okay, this is a molecule that is going to, this is where the ATP is going to be made. You can see by the name, it's a ATP synthase. It's going to synthesize. It's an enzyme because it's ACE. It's an enzyme that's going to synthesize ATP with the help of all these protons. So these protons are going to start being so concentrated that they want to diffuse back. So that's what they do. They diffuse through this ATP synthase. And remember, it's a passive process. It's going to happen naturally because there's so much here and so little here. They naturally float down here. And as they do so, this ATP synthase is going to capture that energy and use it. Okay. It's going to harness that energy from the hydrogens, from these protons diffusing through it to basically. turn ADP into ATP. Turn ADP into ATP. Okay, so adding a phosphate to ADP. So you can see as these hydrons flow through you form so much ATP. Okay, because they as one throws through you form ATP another one you form ATP. So this is where all the ATP is made in bulk. Okay, so that's the key here. Um this whole process, okay, this whole process is called oxidative phosphorylation because These guys, these NADHs, when they drop off their hydrogens and electrons, what's happening when a molecule loses hydrogens and electrons? We call that oxidation. Oxidation is loss of electrons and hydrogens. And then phosphorylation, because here we are phosphorylating ADP. We're adding a phosphate to it with this ATP synthase as the protons are diffusing down through it to turn it into ATP. So we call this whole thing oxidative. phosphorylation. So here is the word for you guys, all this stuff that you need to know. Okay, just know these two are separate I don't want you to confuse electron transport chain leukemia osmosis. The electron transport chain, the main purpose of it is to increase the proton concentration inside the inter membrane space so that these protons want to diffuse back through this ATP synthase to cause ATP to be formed That process here is called chemiosmosis. OK, this whole process, this last step here. So it's separate from the electron transport chains. Chemiosmosis is where the actual ATP is being made. Electron transport chain is where we're preparing all these protons. OK, for chemiosmosis. OK, I hope that makes sense. So now let's take a look at this picture again. We're at the end now. Remember, we had all of these arcade tickets, these NADHs, these FADHs. We have all of them form so that we can. Send them to the electron transport chain to make ATP. Okay. Now remember this I'm going to show you this Sorry, remember this FADH has less value because it pumps less hydrogen's across Remember NADH came to the first electron carrier meaning it caused hydrogen to be pumped here here and here So it caused a lot of hydrogen to be pumped meaning it contributes to more hydrogen's from diffusing through the ATP synthase by chemiosmosis to make ATP. Okay, it contributes to more ATP than FADH because FADH cause less hydrogens to be pumped into this intermembrane space and therefore less ATP will be made because of FADH. That's why we consider it more to be like a broken ticket. Okay, so hopefully that makes sense here. That's why this is where the real ATP is being made. So here we have again a big summary We already looked at glycolysis, link reaction, Krebs cycle. Now the electron transport chain. We can see we make around 32 ATP but we also make water. Don't forget that. This is where water is made. Now, how exactly did we calculate 32? Remember that You should kind of remember this. It's not that important but one NADH molecule has been found Through science studying, through experiments, one NADH contributes to 2.5 ATPs by average. Sometimes it's 3 ATPs, sometimes it's 2 ATPs. So by average, it contributes to 2.5 ATPs, just by average, okay? And then FADH contributes to 1.5. So sometimes 2, sometimes 1, by average 1.5. So if you look at the math, how many NADHs, let's look at here, how many NADHs do we have? Let's just calculate the total amount of ATP. We have 4 ATP, 2 from glycolysis, 2 from Krebs cycle. And then we have 25 ATP because of NADH. Look, NADH, how many do we have? We have 10 of them. Now, each NADH makes 2.5 ATP by average. So 10 times 2.5 is 25. So 25 ATP is because of NADH. And then 3 ATP is because of FADH. Because how many FADH do we have? 2. So 2 times 1.5 is 3. So plus 3. So if we add that all up, we have 32. Okay, let me count properly. 25. So actually from electron transport chain, we only have how many? 25 plus 3. So that's gonna be 28. But, sorry, but if we add these two and these two, we have 32. So overall, you can say for one glucose molecule, we form 32 ATP by average. So like I said, sometimes this number is 2, sometimes it's 3. So this is just a ballpark number. It's not precise. Sometimes it's more, sometimes it's less. So it's just an average number. Don't get too stuck upon this. Okay. So I hope that makes sense. So now coming back to this, this diagram, it should make sense. Our reactants were what? Glucose. Okay. And oxygen. Where did the oxygen react? Right here. Remember? Oxygen was waiting right here to react with the electrons and the hydrogens to form water. So this is where the oxygen is needed. This is why we need oxygen for aerobic respiration. Without oxygen, we couldn't accept these electrons, and therefore we couldn't complete this whole process, okay? We need the oxygen for aerobic respiration. So that's where the oxygen plays a role. We have seen many places where carbon dioxide is made, and we know water is made when oxygen reacts with the electrons and the protons to form water. And we know... There's a few places where ATP is made. The most important place is this whole thing, right? Oxidator phosphorylation, okay? And the chemiosmosis. So hopefully now this little equation makes a lot more sense for you. So you may ask now a good question. Why is NADH and FADH not in this equation? Because, that's a very good question, because they are intermediates. What does that mean? Look, as soon as they are formed, Look, we made NADHs, but as soon as they're formed, they are again used here, directly. So in reality, they are an intermediate product. They are, as soon as they're made, they're used. So therefore, they're not really considered a final product, because as soon as they're made, they're used up. Therefore, we don't actually include them in this equation, because they're just, as soon as they're made, they're used up. Whereas these guys are not, okay? So I hope that makes sense. Okay guys, you guys are surviving it. We're really really close now. It's really the last little bit then we're done with this whole topic So we finished everything here glycolysis, link reaction, Krebs cycle Electron transport chain and chemo osmosis as I promised in the beginning of the video We need to talk a little bit a little bit about anaerobic respiration because remember when we look at this here This whole thing that we've been talking about now Here all of these things here was aerobic, it needed oxygen. So what happens when there's no oxygen? Then this pyruvate will undergo anaerobic respiration. Okay, so we got to talk a little bit about that now. So here we have it. So here we have our glucose, we know it can be split by glycolysis into pyruvate. This whole thing also does not require oxygen. Therefore, we can consider glycolysis as part of anaerobic respiration because no oxygen is required. for the splitting of glucose into pyruvate. Now if there is still no oxygen, pyruvate can either under, I mean if there's oxygen, pyruvate can enter the link reaction and do all the steps that we talked about in this video. If there's no oxygen, it will do anaerobic respiration, continue to do anaerobic respiration. So it will stay in the cytoplasm, it will not go into the mitochondria. So there are two things that can happen depending if you're an animal, if you're a yeast. Hopefully you're an animal, okay? So we got our pyruvate, the three carbon molecule, in animals it will undergo what we call lactic acid fermentation Okay, we're gonna go quickly over this. That basically means we're turning pyruvate, a three carbon molecule, into lactate, another three carbon molecule, by basically causing this to happen. Notice this is the exact opposite. Normally, right, these NAD, NAD+, wants to take electrons and hydrogens and get turned into NADH, but here it's the opposite. NADH is going to drop off electrons and hydrogens and get turned into NAD. Okay, so this is very cool. And the key thing you need to take away from here is that you can see during anaerobic respiration in animals we can recycle this NAD plus Okay by turning NADH into NAD plus because this NAD plus is very important in glycolysis and the other steps to To take electrons and hydrogens, right? We saw to form that ticket. So this is one way in which we can recycle um um nadh and turn it back into nad plus okay very cool so here's some words i'm not going to talk much about this because we talked about this in the sl video i just the extra thing we needed to add here was this guys it can be recycled okay now if you're a yeast something else happens you get turned into a two carbon molecule okay so remember here in animals it stayed three carbons this one is two carbons so we know there must be a step where we lose carbon and there is we lose carbon and again We don't lose it alone. We lose it in the form of carbon dioxide. Okay, that's very important now the same thing as in Animals there is recycling so we turn nadh into nad plus so nadh is Oxidized it loses hydrogen and electrons. Okay, so pyruvate here is reduced because it gains hydrogen and electrons So again not going to talk much about that the key thing that's cool here Is you can see we're making a lot of carbon dioxide so bakers like to use um this is this is useful in baking because this can cause bread and stuff to rise okay that's why they like to add yeast into certain baking ingredients okay that's pretty cool and also you can make alcohol like this ethanol ethanol is um all alcohol that you can drink vodka wine whatever it contains ethanol all of them okay so ethanol is alcohol okay that's it very important now the last little bit can we talk now this right we talked about this whole thing now we got to talk about respiratory substrates. So this will be really really kind of quick, okay? So we know, we just talked about glucose, but remember remember glucose is not the only thing that can be turned into ATP. We got other molecules and they will join this cycle in different stages. You don't need to know any detail, you just need to know that other respiratory, other substrates like lipids and amino acids can also be turned into ATP. Let me show you. So for example, there are some Other kinds of sugars besides glucose that can also undergo glycolysis and therefore kind of contribute to making ATP There are other things like amino acids and lipids look here lipids that can basically get broken down into acetyl-CoA Okay, which will therefore join the Krebs cycle, but they get turned into acetyl-CoA through some other mechanism not this mechanism Okay, but see they can also be used to make energy. That's very important. So I'll put the words here amino acids Lipids sugars, okay, and then here there are some amino acids that even directly just join into the Krebs cycle Okay, so that's pretty cool So what I really want you to take away from this is that other things other? Macromolecules like amino acids like lipids can also contribute to ATP formation by inserting themselves into different stages Into him of cell respiration. Okay, and one multiple choice questionable question that they could ask you is which one, if I had to ask you one gram of sugar and one gram of a lipid, which one can make more ATP from cell respiration? The answer is lipid. Okay. Not glucose. So lipids store more energy in the same mass as glucose does. Okay. And that's just because lipids, right? They're made up of many carbons and basically the fatty acids can be broken down into many many little acetyl groups which can join Uh here in the krebs cycle. Okay, so lipids can also be a source of energy Don't go too crazy on this. It's just to kind of complete the cycle. Don't get stuck on glucose other respiratory substrates do exist Okay, so I really hope that was useful. Let's do a couple quick questions before we end the video What which stage of cell respiration heals the most atp we know the last one right oxidative phosphorylation When one glucose molecule undergoes glycolysis, which of the following is formed? Okay, the answer is C. Not 1 because there's a net production of 2 ATP. Okay, we make 4 and we use 2. So the net production is 2, not 4. So the answer here is 2 and 3. So it's gonna be C. Last one here. Which molecule is the final electron acceptor in aerobic respiration? We know it's gonna be oxygen guys. Okay. So there was a lot, guys. We covered all of this stuff, but I hope it was useful. I hope it made some sense and that the diagrams helped you out. And we will see you in the next one.

What's up everybody! So in this video we're gonna be talking about cell respiration. You guys have been asking for this video for so long.

It only took me like four months to get it up. But the day came. We're finally here. You guys can have some faith in me again. Before we even start guys, go check out teachme.org if you want some awesome sexy looking notes and lots of IB style questions.

Now back to the video. This video will be a long one. There's a lot of, a lot, a lot, a lot of things you guys gotta learn. But we put a lot of effort into this one. We got a lot of cool diagrams, a lot of nice ways to remember things.

So I really hope this video will help you guys out. So sit back, relax and just absorb as much as you guys can. Put your brain cells together and let's get started. The first thing we're going to do is quickly look at the big picture before we can go into all these like nitty gritty details. OK, so what's what do I mean by big picture?

So real quick, what's cell respiration again? And remember, it is basically the breakdown. of our food into a useful form called ATP because our cells money is ATP we need ATP to pay for all the things to happen in our cells okay glucose and fatty acids they're not useful okay they can't pay for all the things to happen but if we convert them by cell respiration into a useful form like ATP then that's what we need okay we need ATP to pay for everything to happen now a common misconception guys Is that cell respiration only applies to glucose?

No, no, no, no Cell respiration is the process by which we turn our food that may happen to be glucose It could be fatty acids could be amino acids Anything like that cell respiration is the process by which we turn any of our food into with a series of reactions into ATP, okay, so it's not limited to glucose only but that being said for this video We're gonna focus on the process for glucose only Okay, we're gonna focus on the whole thing glucose goes through because glucose is the most important molecule that we care about With regards to making ATP, okay in cell respiration, so make sure to know and not get confused with that So what are we looking at here in a big broad sense? We're looking at the process here that glucose goes through in cell respiration We have our mitochondria here right outside of mitochondria is our cytoplasm So we're basically nice and zoomed into a piece of the cell here with some mitochondria and some cytoplasm And we can see there's a lot of steps that go on. So the four steps are glycolysis, link reaction, Krebs cycles, electron transport chain, and chemiosmosis. This whole aspect here, okay, requires oxygen.

So that's going to be part of aerobic respiration, okay? Pyruvate, when there is no oxygen, okay? When there's oxygen, it will do all of these things called aerobic respiration. When there's no oxygen... anaerobic respiration is going to happen okay and we'll look at that later in this video on a separate slide okay so this is the big picture okay we're going to go into all of these steps in detail all the way from glycolysis to electron transport chain and chemiosmosis okay so just remember this big picture and we're going to come back to this now before we go into the actual individual steps we need to talk about oxidation and reduction i know you guys hate this always because it's so chemistry like but trust me It's not that bad.

There's only a little bit, a very low level that we need to understand about reduction oxidation. A few things you got to memorize because we don't need to know the chemistry details. We're only biology, right? There's only biology.

Don't need to know the teeny tiny things we cannot see. OK, so we're going to quickly go into this and then we're going to go into the details here of cell respiration. OK, so what exactly is reduction oxidation? Basically, these are two kinds of reactions. Let me show you here with a little the little molecules.

So here we got two molecules, the blue one and the green one. Notice the blue one is basically stealing these electrons and hydrogens from this green one, then taking it for themselves. The green one lost it and now is without the hydrogen and the electrons.

Okay, now the molecule that takes hydrogen and electrons from other molecules, we call that process reduction. Okay, so reduction is the process by which a molecule gains hydrogens and electrons. Oxidation is the opposite. Okay, so these guys, this green molecule lost hydrogens and electrons to become naked.

So that's oxidation. Okay, so you can see that oxidation and reduction, they always happen together. You can't have one without the other. You can think of it like the scene from Tintin, where the thief steals wallets from other people.

You can't have a thief without a victim. Okay, very important. The same thing here, you can't have oxidation without reduction. They always happen together.

which is why they give the scientists give it a name called redox reduction and oxidation now Here's a little key table you guys need to know. It can come up for multiple choice questions or even long answer questions So pay attention to this. So as a quick summary Reduction is the gain of electrons or gain of high electrons or hydrogens Oxidation is the opposite loss of electrons loss of hydrogen Then another way of defining reduction is loss of oxygen and oxidation is gain of oxygen I wouldn't worry too much about this last one.

I have it here if you guys want to remember it It's not too important for now. We may come back to it later in this video But the very key ones that you need need need to remember right now is this for oxidation and reduction Um, okay. Now here's a way to remember it. You guys have probably seen it.

Your teachers probably mentioned oil rig to you guys Oxidation is loss of electrons and hydrogens reduction is gain of electrons and hydrogens So that's the big idea. See it's not too much Just remember these things because it's going to come up and up again throughout this video I'm going to mention these words a lot So keep this in your brains and you'll see we're going to reuse it throughout this video So it will get engraved in there. Trust me. So now We are gonna now we finished the big picture and redox.

Okay, these are the two painful parts we had to finish now We're gonna go into the real stuff you guys want to learn about right? So first um, we gotta look at the equation of Um cell respiration this guys you probably have seen this right glucose. Sometimes you see it in equation form like this Sometimes you see it in word form Don't worry about it.

We're gonna look at this now and we're gonna look at it again at the end of this video And it will make hopefully it will make much more sense at the end of this video So you can see it's glucose plus oxygen will yield or form carbon dioxide water And of course our atp right now ain't gonna make sense But just take a look at it absorb a little bit and we're gonna come back to it And you're gonna see that it makes a lot of sense. So now let's get into our glycolysis the first step here Okay, the first step here. So where are we first? Where are we?

We're here, this is the mitochondria and outside we have what? We have our cytoplasm. Okay, so glycolysis happens in the cytoplasm.

That's super important to understand. Now glycolysis literally means splitting, lysis means splitting, of glucose or splitting of sugar. So you can imagine what's going to happen in this step, right, in glycolysis.

So let's start here, up here. Here we have our glucose, right? That's the thing we're going to turn into ATP.

So that's our initial starting point. Now You may be like why is it in a chain like this? I thought glucose looked a lot like this. You're right glucose is actually in this shape right?

It's a structure like this. It's got one, two, three, four, five, six carbons, some hydrogen, some oxygens. This is actually how glucose looks like but for the sake of explanation of this whole cell respiration process we're going to make it in a linear form okay?

It's how they use it in textbooks. It's easier to understand and that's how they want you to remember it but do bear in mind that glucose actually has this shape. not a linear structure, okay? Just for explanation purposes. So the first thing that happens is glucose is going to react with ATP, and that's crazy.

So we're using ATP in the very first step of cell respiration. I thought we're trying to form ATP. Isn't this defeating the purpose?

You're right. It's crazy, right? But it's going to make sense.

You'll see later in this video. So we do need to use ATP for the first step. Why?

Remember, ATP is called adenosine triphosphate, so it's a molecule. with three phosphates. Now each ATP is going to add one phosphate group to this glucose.

So you can see we have two ATPs which means we're going to add two phosphate groups to this glucose. So we're ultimately basically forming this. Okay we're forming a molecule that has two phosphates added. Okay and in the process of adding these phosphates these ATPs get converted into ADP because ADP is adenosine diphosphate.

Di meaning two phosphates. So each ATP dropped off one phosphate to form ADP. So now, okay, that's kind of strange.

So now we have this molecule here with two phosphates added. Okay, so what was this process called of adding these phosphates to glucose? It's called phosphorylation.

Okay, phosphorylation. So remember this, phosphorylation, adding a phosphate. Okay, that's the very first step. So now we have this molecule called fructose 1,6-biphosphate.

Okay. There's very few names you guys are gonna have to remember for the whole cell respiration process and this is one of them Okay, unfortunately, you may need to remember this name, but i'm going to help you try and explain why it makes sense Look, what does this 1 6 deal with? Look, this is the first carbon and this is the sixth carbon or you can think of it as this is the first carbon And this is the sixth carbon. So on the first and the sixth carbon we have a phosphate. Okay So that's kind of why there's a 1 and a 6 there.

Okay, why is it called bisphosphate and not biphosphate? Why is the S there? Okay, when we use biphosphate, that means that the phosphates are on adjacent carbons. But we can see that these phosphates are not on adjacent carbons.

This phosphate on the first carbon and the other phosphate is on a carbon very, very far away. In that scenario, we say bisphosphate instead of biphosphate. If the phosphate, if the two phosphates were on adjacent carbons, we'd call it biphosphate. So that's why this whole thing is called fructose 1,6-biphosphate. You don't need to know why it's called that, but just try and...

hopefully that can help you remember this name a little bit better. Okay, so that's our first step. Now, these phosphates...

By adding these phosphates, this molecule is very unstable. So phosphates make a molecule relatively unstable. Basically, it makes it want to react.

So this molecule is not stable and now it's going to react. What's it going to do? Guess what?

It's going to split. It's gonna undergo splitting lysis. So that's where this lysis comes from.

So finally this molecule is gonna split in two Look now we have two molecules that are identical three carbon molecule with a phosphate attached. We call these triose phosphate Okay, because they got three carbon so triose because ose remember means sugar So this is a sugar triose and it's got a phosphate now. So that's lysis.

Okay phosphorylation Lysis now each of these triphosphates will undergo now a bunch of steps So i'm only going to show it here for this one. But but bear in mind the same thing happens for this side Okay. Ah look here now now your oxidation reduction knowledge will have to come together Look at this molecule. You can think of it like a guy called nad. Okay nad this molecule is super super interesting It loves to take things from other people.

It's like a thief Okay, so it's a lot like this scenario here. Let me go back to it's like this thief guy. It loves to take things Now, what is it like to take? It likes to take, let me show you, hydrogens and electrons. Look, this guy, NAD positive.

It's going to try and take hydrogens and electrons from this triose phosphate. Okay. And in the process of doing that, it becomes NADH.

See, now it's got a hydrogen and it's got some electrons. So we call it NADH. Okay.

Hmm. So what do we call that again? I must, I must emphasize on this.

So what's the process called when, say, so this molecule loses triose phosphate. loses hydrogens and electrons to this guy here. So when the molecule loses hydrogens and electrons, what happened?

We call that oxidation. So this guy, when it loses its electrons and hydrogens, we call that oxidation. So guess what? This whole process we call oxidation and reduction.

Because remember, reduction, I mean oxidation, never happens without reduction. How does that make sense? Remember, triose phosphate lost the hydrogens and electrons, so it was oxidized.

But something else gained the hydrogens and electrons. This NAD+, right? It gained the hydrogen and electron, so it was reduced. So we can say that triose phosphate was oxidized and this NAD was reduced to form NADH. Okay, very very important.

So step one, phosphorylation, lysis, now oxidation and reduction. Now you may be like, okay great, what the heck was the point of forming this NADH? Think of this NADH like a ticket, an arcade ticket.

This is gonna help you a lot. It helped me a lot. Okay, you know in arcades when you play games and you win all these tickets They're kind of useless.

There's a piece of paper But if you win enough of them, you can trade them in for a big gift Okay at the at the counter, right you can if maybe if you have a hundred of them You can get a big prize or something, right? So think of these NADH is like an arcade ticket We're gonna try and build up a lot of these NADH throughout this whole cell respiration process because at the end of the day We're gonna use these NADHs, these RK tickets and trade them in for a lot of ATP, okay? So that's what I want you to think about these NADHs as.

They're like a little RK ticket. Very very cool. Okay, so other than that oxidation reduction, we also add a phosphate here, okay?

So now we form a molecule here that is three carbons with two phosphates because we just added a phosphate, okay? This is different from this scenario here because this phosphate here came from ATP, okay? This phosphate is free-floating.

It's called inorganic phosphate. When a phosphate is free floating, not attached to any other molecule, it's kind of just by itself like a loner, we call it an inorganic phosphate. Don't worry, I'll reveal all the words here later, okay? So this inorganic phosphate is now going to attach, so now we have these molecules, okay? Three carbons and two phosphates, okay?

Awesome. Now, finally, the last step of glycolysis is this. So now we have ADP that are going to take these, that's going to take these phosphates off. So One ADP will come and take a phosphate to form ATP, then another ADP will come and take the other phosphate to form ATP, ultimately resulting in a molecule that has no phosphates and it's just three carbons, which we call pyruvate. Okay, so what do we call this little step here?

ATP formation. Okay, because we formed some ATP. Okay, awesome. Remember the same thing happened on this side. Okay, so now now I want to tell you what this big brain trip was for.

Look, if you want the one great way to remember the order of this is thinking of this people love outdoor activities. And this is how I used to teach it. But now, because nowadays things change, we're going to call it online activities. People love to be inside.

So why the hell not just call it online? Okay, so it's you can remember if you maybe you're an outdoor person. You can call it people love outdoor activities, but you can also remember it as people love online activities.

Okay phosphorylation p l lysis oxidation atp formation this is important because i've seen Some multiple choice question where they ask you to to arrange the order of these of these steps Okay, so you should know the order. Okay, so that was it for glycolysis. I want to look at the ultimate summary What did we really make in glycolysis? We made two atps.

Do you agree with that? No You should be like no right because we made two atps here and two atps here. So shouldn't that be four? That's a good way to think about it. But remember although we formed four atps We spent two atps so four minus two is two so we only actually Net the net amount of atp was two.

Okay, because we made four and lost two So we actually only made two and then we made two nadhs right one here and one on this side And then we made two pi rubates right one here one there. Okay, so that's very cool So here is the steps written out as promised everything I said this is all the important stuff you need to know So now let's go on to the next stage here next stage So coming back to our original diagram, remember i'm gonna now fill it in as we go along So we had glucose we underwent glycolysis by a bunch of steps, right? People love online activities to form pyruvate two of them right two pyruvates and in the process we made some stuff some atp But we made these tickets two nadhs these tickets that later We want to trade in at the last stage here for ATP.

So these tickets, these NADHs are really important to remember about them. Okay, awesome. So now, good. We finished now glycolysis. Let's go to the link reaction.

Okay, so here we are. Where the heck are we now? Okay, now we're looking. Okay, I want to make this clear.

We're basically zooming in. Okay. You can see this picture.

We're basically zooming into the matrix area with a little bit of membrane Okay, remember for the mitochondria this outer layer is called the outer mitochondrial membrane And then this inner membrane that bends and curves like this is called the inner mitochondrial membrane and then this space right outside Okay, the space in between the outer mitochondrial membrane and the inner mitochondrial membrane that's called the inter membrane space Okay inter membrane space. So right now we're kind of looking at the matrix and a bit of the the membrane okay, the inner mitochondrial membrane. You'll see why.

Okay, so what's going on with the link reaction? So remember we just made pyruvate in the cytoplasm outside of the cell, right? Going back to it.

We made pyruvate here in the cytoplasm, in the cytoplasm outside of the mitochondria. So now our pyruvate is going to be pumped into the mitochondria from the cytoplasm using some active transport, okay? So pumping it into the matrix. We got to pump it into the matrix now.

Now, so now we have a pyruvate brought all the way from the cytoplasm of the cell into the matrix, okay? Now, what is the link reaction exactly do? So we have a three carbon molecule, the pyruvate, and remember, remember this, okay?

I don't want to confuse you guys here. Remember we formed two pyruvates. So what I'm explaining now with the link reaction is gonna happen for both pyruvates, okay?

So I'm gonna show it with one pyruvate, but remember It's happening with the other side as well, okay? It's not just happening with one pyruvate, so remember that. Okay, so what happens with the pyruvate?

Okay, couple things. First, we got our little ticket man. NAD plus is gonna take more electrons and hydrogen to form NADH.

What do we call that again? Oxidation and reduction. The pyruvate is oxidized because it loses electrons and hydrogen, and the NADH is reduced because it gains hydrogen and electrons. Okay, so that's gonna be our little ticket guy.

We'll put the words here for you guys. So oxidation and reduction is gonna happen again. Now also, this 3-carbon pyruvate is gonna lose a carbon, okay, to form a molecule called acetyl. Acetyl. Okay, it loses this carbon in the form of carbon dioxide.

Carbon dioxide. Okay, so I'm gonna put a carbon dioxide here. Because this carbon isn't lost just as a carbon. It comes off in the form of carbon dioxide. Okay, so remember that.

And that... is already helpful here because look one of our products of cell respiration is carbon dioxide so you can see where this carbon dioxide comes from okay Okay, so that's cool. So we underwent oxidation and reduction. We lost a carbon.

What do we call that process when we lose a carbon as carbon dioxide? We call it decarboxylation, okay? Because we have this carbon dioxide that comes off in the form, this carbon that comes off in the form of carbon dioxide. So that's called decarboxylation. Now, the last thing that happens is we have this little molecule called coenzyme A that's going to add on, okay?

So you can see the final product we formed. Therefore... is acetyl CoA because we have this two carbon molecule called acetyl plus this coenzyme A. So we call it acetyl CoA. Okay?

I want to emphasize right now while I'm thinking about it, remember when I talk about all these steps like glucose turning into this and this doing that, what is catalyzing these reactions? Do they happen magically by themselves? No, right?

Remember each step has their own unique enzyme. Remember an enzyme is a little molecule, a little tool that catalyzes and makes things happen like a hammer or like a screwdriver. It's a little thing that makes a specific reaction happen and each step will have their own unique enzyme.

I'm not showing it here but remember that. No reactions just spontaneously happen, they normally use an enzyme right? So it's the same thing here, there will be an enzyme here catalyzing this reaction. But you guys don't need to worry about the name of that enzyme or anything like that.

Okay, give me a sec. So what did we form in the link reaction? Okay, two carbon oxides.

You might be like why I thought we only formed one No, we formed two because remember there are two pyruvates. I'm showing you one pyruvate But when we break down one glucose we form two pyruvates each pyruvate will undergo a link reaction So we'll actually form two carbon oxides for one glucose molecule, right and same here two NADHs Okay, not just one because there's another pyruvate same here two acetyl coase. Okay, so you can see already I just want to show you this From the glycolysis, the products were 2, 2 and 2. Okay, it's the same thing here. Okay, 2, 2 and 2. Okay, so let's write now the words of what you need to know.

Okay, here's the words for you guys. Make sure I don't screw anything up here. I don't know why. Give me a second, guys. I don't know what happened here.

I don't think that should be there. Okay. That's it for you guys. So where are we now? So we have now, our glucose underwent glycolysis to form two pyruvates.

Each pyruvate went into the matrix of the mitochondria where we underwent the link reaction to form acetyl-CoA. In the process, we made some of those tickets, right? Two NADHs that will, again, these guys will be traded in later for ATP. All right.

So where are we at now? We did glycolysis. We did the link reaction.

Now we're getting to the Krebs cycle. Okay, the Krebs cycle. So the Krebs cycle is a hell of a thing, guys. You guys will look at it and be like, oh, I don't want to do this anymore. But trust me, it's not that bad, guys.

Come on. So remember now we did the link reaction, right? I'm going to re-show you it here just for clarity's sake. We got our pyruvate. Remember, it got pumped into the matrix of the mitochondria where it underwent what?

The link reaction to form what? Acetyl-CoA. Okay, I didn't show the other things made because we're just recapping it here. Now, now this acetyl-CoA is going to enter what we call the Krebs cycle. Okay, the Krebs cycle.

I cannot for the life of me think of a nice way to remember that the Krebs cycle is part of cell respiration. If you guys can write it in the comments, I'd love to know it because a lot of the times students get confused because they don't remember if the Krebs cycle is part of photosynthesis or part of cell respiration. But I can think of a nice way to remember it.

If you guys can, please let me know. But another way. To call the Krebs cycle is the citric cycle or the citric acid cycle. Okay. Now you can think of this Krebs cycle as a little analogy.

Okay. I'll kind of give you an analogy like a little Ferris wheel. So you got this, this people, um, four people.

Okay. A four carbon molecule, which we call oxaloacetate. Four carbon. You guys need to know that name. Any, every time I put the name, you actually need to know it.

Okay. So make sure you know this name. There's this four carbon molecule. Okay. There's four people on this, on this, on this, uh, Ferris wheel box.

Okay. and they come down and now these two people or this acetyl-CoA is going to try and join these people so now we have six people on this ferrous wheel box okay so that's what happens this acetyl-CoA combines with oxaloacetate to form a six carbon molecule which we call citrate again please remember this name you need to know it okay you need to know both of these the other ones you don't need to know but oxaloacetate and citrate you need to know now as this acetyl-CoA combines with oxaloacetate this This coenzyme A comes off. As you can see, it's not here. It's not in the 6-carbon molecule. So it gets recycled.

Okay, it gets recycled So that now this coenzyme is free again to combine with the next pyruvate so that another acetyl-CoA can be made Okay So this CoA molecule is really only useful to be able to combine with to combine this These two carbons with these four carbons after that it's it's not needed so it gets recycled So that's that's important to understand now this six carbon molecule something's gonna happen. Okay, two things again oxidation and reduction because guess what this NAD plus is going to take what? Electrons and hydrogens for itself to form NADH, this arcade ticket, right?

So that's what we call that again. That means this, if these electrons and hydrogens were taken from the six carbon molecule, that was oxidation. And this NAD plus was turned into NADH, we call that reduction.

Okay? So that's oxidation and reduction happened here again. And guess what? The six carbon molecule gets turned into a five carbon molecule. Okay?

Because the six carbon one carbon comes off as a carbon dioxide. Okay, what do we call that again? Decarboxylation don't worry.

I'm going to put the words very soon So you guys can think of this as a little like story So these four people join these two people now, there's six people the one person gets sick on the ferrous wheel, right? He's like, oh, I can't do this no more and he and he hates it that much he jumps off So now we have five people left. Okay. Now now this ferrous wheel box only has five people now this five carbon molecule again It's gonna go undergo oxidation, okay?

It's gonna lose electrons and hydrogens to this NAD+. Okay, so the five carbon molecule was oxidized and this NAD plus was reduced. So we got more of these tickets. You can see these tickets, these arcade tickets are building up. Now, surprise surprise, another person gets sick and they jump off the, uh, they jump off, okay?

So we have another decarboxylation, another carbon comes off as carbon dioxide, remember? So Another person jumps off now. We have four people left on this on this ferrous wheel.

Okay now what? Very very similar pattern guys you guys will see so now we have again this oxidation and reduction to form NADH Okay, but now we have this other cool thing. There's another molecule Wait, let me take a sip of this coffee. My throat's going very dry. Okay Now we have another molecule that's very similar to NAD plus It's called FAD+.

Now this molecule, just like NAD+, likes to take electrons and hydrogens from other molecules. Okay, so as it does so, it forms FADH2. Okay, and you can think of this guy as like a broken arcade ticket. So when this guy goes and returns or tries to trade in the NADH arcade ticket, he's gonna get a lot of ATP. Okay, because it's a good, it's a fresh ticket, but this FADH2 It's gonna the guy at the counter is gonna be like, but your ticket's a bit broken So I'm not gonna give you that nice of a price because your tickets a bit broken So that's what I want you to remember FADH2 is like a broken ticket.

It's not as valuable as NADH Later on to get ATP. Okay, so it's still a ticket but it's not as valuable. It's like a broken ticket now very important What's unique about this this stage here is we're actually making ATP So you can see an ADP here is gonna come in and take a phosphate Which we didn't show here but taking a phosphate to make ATP.

Okay, so in this step here, we actually have ATP formation Okay, very very good So now guess what we did after all these steps we regenerated this oxaloacetate Okay So now we're back to this four carbon molecule Now it can combine again with an acetyl CoA and the cycle can repeat and we can keep building up a lot of NADHs So I want to quickly stress something remember from the enzyme video This would be a cyclic metabolic reaction. Remember you have linear metabolic reactions and you have cyclic metabolic reactions This would be a cyclic one because it's a cycle you regenerate this molecule as you go around. Okay, let's put some words So what happened really here? We have ATP formation. Remember here we have how many d carboxylations?

Two, okay. Let me put it here. Where where do we have it? We have one Decarboxylation here turning six carbon into five carbon and then we have another one here turning five carbon into four carbon But then we stay at four carbon.

So we don't have another decarboxylation. We only have two so it's again It's two and then how many oxidations and reductions do we have? Let me move this a bit guys.

Sorry We have four. Okay. Sorry high tech here.

Okay four Because we got one here, one oxidation reduction, another one here, that's two, and then we have one. that's oxidation reduction but it's FAD and then we have one another one that's NAD so in total we have four oxidation and reduction reactions in one Krebs cycle. Okay so from Krebs cycle what's our final products? How many how many NADHs do we have? You can count here one two three but why did I put six because we have this Krebs cycle happens twice right because we have two pyruvates so we showed one pyruvate getting turned into acetyl CoA so we showed you one Krebs cycle but remember we have another pyruvate that's also going to do this.

So Krebs cycle for one glucose molecule, the Krebs cycle will technically make six NADHs, not three. Okay, same. So we double everything.

So we have four carbon oxides, not two, because it happens twice, and we have two ATPs, not one. Okay, so that's important. So hopefully that idea makes sense. Let me show you now the word form of that.

So you can remember the analogy, it's going to help you, the four carbons. Four people join the two people you have six people one gets sick jump off Another one gets six jump off and now we're back to four and it stays four Okay, but what I can tell you for sure is at every single step at every single step we have oxidation and reduction oxidation and reduction this here we have oxidation reduction here We have oxidation reduction here. We have two oxidation and reduction But only in the last step do we have atp formation not in the first two so you can look at that Hopefully it helps you out But here's the word summary of all the steps you guys really gotta know. Okay, so let me show you here now our diagram again. So what did we do so far?

We did our glycolysis, got a bunch of products including our tickets, link reaction got the tickets, and remember Krebs cycle we got six NADHs and two NADH2s which is the broken ticket. So we got a lot of these tickets and they're all now heading to this last step here of the electron transport chain and chemiosmosis where we're going to form all the ATP. Because you guys can see so far how much ATP did we really make basically nothing, right?

Like we made one here in the maybe two in the krebs cycle for two krebs cycles we made Um, not we made nothing in the link reaction and we made only two in glycolysis So we basically made no ATP. So all the ATP must be made in this last step, right? So here I just want to show you a quick summary. This is actually to test you guys so here I have glycolysis the link reaction and the krebs cycle I want you guys to Put the number of each of these things formed to see if you remember well test yourself Okay, these things these little details are very easily quizzed upon in multiple choice.

Okay, they love to do it So make sure you know it i'll show it to you guys So here you are It's very easy to remember for the first two because it's two two and two for this one It's two two and two just for the last one. It's more like two four six Okay, there's like a bunch of mix there so you guys can try and remember that. Okay? So guys, where are we now? We finished glycolysis, we finished the link reaction, we finished the Krebs cycle, and we're now going into the etc.

No, we're going into the electron transport chain and chemiosmosis, okay? That's the last little bit here so we can finally see where all that ATP is coming from, guys. So where does this last step happen?

Where is the electron transport chain and where does chemiosmosis happen? Well, look at our mitochondria. It happens in the mitochondria, but specifically, it happens...

I want to move this for you guys. It happens there, right here, at this area here, the inner mitochondrial membrane, the outer mitochondrial membrane, and this inner mitochondrial membrane space. So this one doesn't really happen primarily in the matrix, it happens there.

So you can see here from this diagram, I tried to label it for you guys, this membrane here is our inner membrane, so that's our inner membrane here, then we got this big space in between the inner membrane and the outer membrane, so it's the outer membrane, we call that the intermembrane space. and then outside of that we have the cytoplasm of our cell and then inside here we have the matrix the inner side of our mitochondria so we know the link reaction and the krebs cycle was happening here in the matrix so now we're going to come here to this little membrane area okay so what's going on here do you remember that we built up all of this like let me come back to it all of this nadh and fadhs all these rk tickets they're going to become really really really important here Okay in the electron transport chain, let me show you so here we have it we have our nad dhs Okay, we're first going to talk about those remember they are carrying all of these hydrogens and electrons, right? So they now they come to this inner membrane and what they do is they come to these little guys here What do we call these guys here? These guys are electron carriers this one this one this one this one this one this last one is not and we're gonna get to What that one is?

But basically these first three, I mean these these first batch here these guys Is our electron transport chain electron transport chain and what they do is exactly what the name says They transport electrons. We're gonna see how so these individual guys they're called electron carriers Okay, so all of these electron carriers form our electron transport chain and in this last guy here is called our ATP ace And it's gonna be responsible for chemiosmosis. Okay, we'll see how what that is later So anyways, remember we had all of our little tickets, right? Our NADHs, they were built up and all that. So they're all accumulating now here in the matrix.

So what they do is they now go to this inner membrane and they decide, you know what, I'm tired of carrying all these electrons and hydrogens. I'm going to drop them off. And he basically drops off these electrons to these electron transport chain.

And also it drops off the hydrogens. OK, so it drops off the hydrogens. So here we have some hydrogens. and it drops off its electrons.

Now the electrons, okay look look look at this, the electrons when they're dropped off this electron transport chain, all of these electron carriers are gonna basically play game of hot potato. So this one gets the two electrons and it's gonna pass it to the next one. It's gonna be like I don't want it, I'm gonna pass it to the next one. That one don't want it, it's gonna pass it to the next one.

That one don't want it, pass the next one. So this is an electron transport chain because they're transferring the electrons that were dropped off by this NADH. Okay. Now these electrons, they're high energy, okay? They're high energy.

Electrons are high energy. So what they do is, as soon as this NADH drops off these electrons, okay, this is going to activate this-these electron carriers to pump hydrogen across. Because remember, remember this, the NADH not only dropped off electrons, but also hydrogen, okay? But it drops them off here. The hydrogen is in the matrix.

So there's no way the hydrogen can just go through unless it's pumped through by this electron carrier. So what stimulates that- pumping it's these electrons they're high energy so as they pass through these electron transport chains they stimulate these pumps to pump hydrogen into this inter membrane space this teeny tiny little space okay teeny tiny little space and this is actually interesting you can see how this inner membrane folds so much the reason why it folds so much is to increase the surface area so that so that this process can happen everywhere so we can pump as much hydrogens into this inter membrane space as possible because if there wasn't that much folding there wouldn't be that much area for this whole process to happen so all this folding is creating a very large surface area for this to happen a lot so we can pump in a lot of hydrogens so anyways yeah these electrons pump come in they cause these electron transport chains to pump in the hydrogen okay and not only this one it's gonna get eventually get passed down the electron transport chain and cause this one to also pump in hydrogen and this one to also pump in hydrogen right Okay, so basically pumping in a lot of hydrogen. Okay, a lot of hydrogen a lot of protons, right?

We call these protons So when a hydrogen has no electrons because remember this NADH here it was carrying electrons and hydrogens So when the when this hydrogen has no electrons because the electrons went here we call it a proton So you'll see the word proton. So proton is a hydrogen with no electron. Okay, it's called a proton So now these protons are being pumped into this inter membrane space Now look, so that keeps happening. Now where the heck is the FADH? The FADH is interesting because it doesn't actually come So early.

It doesn't start, it doesn't go to the first electron carrier. It goes later. Okay, so it comes more here So you can see here instead of instead of sending its electrons to the first electron carrier It sends it to the second one which means the electrons from this FADH2 Is not gonna stimulate this first one. It's only gonna stimulate the second one. So that means that this FADH It's only gonna activate these two guys to pump hydrogens So the FADH is gonna cause less hydrogen pumping than the NADH did because remember the NADH is sending electrons That will cause this one to pump hydrogens this one to pump hydrogens and this one but the FADH is only sending electrons here So it's only gonna activate this one and this one so less hydrogens will be pumped into the intermembrane space for the FADH2.

That's why we consider it like a broken ticket. And you'll see why we call it broken ticket. Okay, give me a second. So same thing here. Okay, same thing here.

Now finally, when these electrons reach the end, okay, they reach this last electron carrier, they need to eventually be accepted because otherwise where do they go? Okay. They need to be accepted by someone.

So guess what accepts this electron? Oxygen. Look, we have an oxygen here.

Okay, this oxygen is going to accept these electrons at this last electron carrier in addition to all of these In addition to two protons because remember these NADHs they kind of let go of these protons So in this matrix, we have a few protons eventually A lot of them are pumped into this inter membrane space, but there are still some remaining Now this oxygen will accept these electrons in addition to two hydrogens to form guess what water because water is H2O two hydrogens and oxygen Okay, so you can think of oxygen as the final electron acceptor because it's going to accept these two electrons along with Two protons to form water. Guess what coming back to our picture here. We got our water. That's where water is formed So we see now where all the carbon dioxide is formed and we see where the water is formed.

Okay, give me a sec Okay Of course hydrogen is still pumped. Okay, so what we're doing, what we did now, all of these arcade tickets, basically what they did is they caused a lot of protons to be pumped into this intermembrane space. So it's building up and building up and building up and becoming super super concentrated.

So we have a huge proton gradient. We have a lot more protons in the intermembrane space than we do in the matrix. So there's a there's a gradient.

So these protons want to diffuse down, want to diffuse back to even out that concentration gradient. Okay, but they can't go through any of these guys. They need to go through a specific kind of transporter that we call ATP synthase.

Okay, this is a molecule that is going to, this is where the ATP is going to be made. You can see by the name, it's a ATP synthase. It's going to synthesize.

It's an enzyme because it's ACE. It's an enzyme that's going to synthesize ATP with the help of all these protons. So these protons are going to start being so concentrated that they want to diffuse back. So that's what they do.

They diffuse through this ATP synthase. And remember, it's a passive process. It's going to happen naturally because there's so much here and so little here.

They naturally float down here. And as they do so, this ATP synthase is going to capture that energy and use it. Okay.

It's going to harness that energy from the hydrogens, from these protons diffusing through it to basically. turn ADP into ATP. Turn ADP into ATP. Okay, so adding a phosphate to ADP. So you can see as these hydrons flow through you form so much ATP.

Okay, because they as one throws through you form ATP another one you form ATP. So this is where all the ATP is made in bulk. Okay, so that's the key here.

Um this whole process, okay, this whole process is called oxidative phosphorylation because These guys, these NADHs, when they drop off their hydrogens and electrons, what's happening when a molecule loses hydrogens and electrons? We call that oxidation. Oxidation is loss of electrons and hydrogens.

And then phosphorylation, because here we are phosphorylating ADP. We're adding a phosphate to it with this ATP synthase as the protons are diffusing down through it to turn it into ATP. So we call this whole thing oxidative.

phosphorylation. So here is the word for you guys, all this stuff that you need to know. Okay, just know these two are separate I don't want you to confuse electron transport chain leukemia osmosis. The electron transport chain, the main purpose of it is to increase the proton concentration inside the inter membrane space so that these protons want to diffuse back through this ATP synthase to cause ATP to be formed That process here is called chemiosmosis.

OK, this whole process, this last step here. So it's separate from the electron transport chains. Chemiosmosis is where the actual ATP is being made. Electron transport chain is where we're preparing all these protons. OK, for chemiosmosis.

OK, I hope that makes sense. So now let's take a look at this picture again. We're at the end now. Remember, we had all of these arcade tickets, these NADHs, these FADHs. We have all of them form so that we can.

Send them to the electron transport chain to make ATP. Okay. Now remember this I'm going to show you this Sorry, remember this FADH has less value because it pumps less hydrogen's across Remember NADH came to the first electron carrier meaning it caused hydrogen to be pumped here here and here So it caused a lot of hydrogen to be pumped meaning it contributes to more hydrogen's from diffusing through the ATP synthase by chemiosmosis to make ATP.

Okay, it contributes to more ATP than FADH because FADH cause less hydrogens to be pumped into this intermembrane space and therefore less ATP will be made because of FADH. That's why we consider it more to be like a broken ticket. Okay, so hopefully that makes sense here.

That's why this is where the real ATP is being made. So here we have again a big summary We already looked at glycolysis, link reaction, Krebs cycle. Now the electron transport chain.

We can see we make around 32 ATP but we also make water. Don't forget that. This is where water is made. Now, how exactly did we calculate 32?

Remember that You should kind of remember this. It's not that important but one NADH molecule has been found Through science studying, through experiments, one NADH contributes to 2.5 ATPs by average. Sometimes it's 3 ATPs, sometimes it's 2 ATPs.

So by average, it contributes to 2.5 ATPs, just by average, okay? And then FADH contributes to 1.5. So sometimes 2, sometimes 1, by average 1.5.

So if you look at the math, how many NADHs, let's look at here, how many NADHs do we have? Let's just calculate the total amount of ATP. We have 4 ATP, 2 from glycolysis, 2 from Krebs cycle. And then we have 25 ATP because of NADH.

Look, NADH, how many do we have? We have 10 of them. Now, each NADH makes 2.5 ATP by average.

So 10 times 2.5 is 25. So 25 ATP is because of NADH. And then 3 ATP is because of FADH. Because how many FADH do we have?

2. So 2 times 1.5 is 3. So plus 3. So if we add that all up, we have 32. Okay, let me count properly. 25. So actually from electron transport chain, we only have how many? 25 plus 3. So that's gonna be 28. But, sorry, but if we add these two and these two, we have 32. So overall, you can say for one glucose molecule, we form 32 ATP by average.

So like I said, sometimes this number is 2, sometimes it's 3. So this is just a ballpark number. It's not precise. Sometimes it's more, sometimes it's less.

So it's just an average number. Don't get too stuck upon this. Okay. So I hope that makes sense.

So now coming back to this, this diagram, it should make sense. Our reactants were what? Glucose.

Okay. And oxygen. Where did the oxygen react?

Right here. Remember? Oxygen was waiting right here to react with the electrons and the hydrogens to form water. So this is where the oxygen is needed. This is why we need oxygen for aerobic respiration.

Without oxygen, we couldn't accept these electrons, and therefore we couldn't complete this whole process, okay? We need the oxygen for aerobic respiration. So that's where the oxygen plays a role.

We have seen many places where carbon dioxide is made, and we know water is made when oxygen reacts with the electrons and the protons to form water. And we know... There's a few places where ATP is made. The most important place is this whole thing, right?

Oxidator phosphorylation, okay? And the chemiosmosis. So hopefully now this little equation makes a lot more sense for you. So you may ask now a good question. Why is NADH and FADH not in this equation?

Because, that's a very good question, because they are intermediates. What does that mean? Look, as soon as they are formed, Look, we made NADHs, but as soon as they're formed, they are again used here, directly.

So in reality, they are an intermediate product. They are, as soon as they're made, they're used. So therefore, they're not really considered a final product, because as soon as they're made, they're used up. Therefore, we don't actually include them in this equation, because they're just, as soon as they're made, they're used up. Whereas these guys are not, okay?

So I hope that makes sense. Okay guys, you guys are surviving it. We're really really close now.

It's really the last little bit then we're done with this whole topic So we finished everything here glycolysis, link reaction, Krebs cycle Electron transport chain and chemo osmosis as I promised in the beginning of the video We need to talk a little bit a little bit about anaerobic respiration because remember when we look at this here This whole thing that we've been talking about now Here all of these things here was aerobic, it needed oxygen. So what happens when there's no oxygen? Then this pyruvate will undergo anaerobic respiration.

Okay, so we got to talk a little bit about that now. So here we have it. So here we have our glucose, we know it can be split by glycolysis into pyruvate.

This whole thing also does not require oxygen. Therefore, we can consider glycolysis as part of anaerobic respiration because no oxygen is required. for the splitting of glucose into pyruvate. Now if there is still no oxygen, pyruvate can either under, I mean if there's oxygen, pyruvate can enter the link reaction and do all the steps that we talked about in this video.

If there's no oxygen, it will do anaerobic respiration, continue to do anaerobic respiration. So it will stay in the cytoplasm, it will not go into the mitochondria. So there are two things that can happen depending if you're an animal, if you're a yeast.

Hopefully you're an animal, okay? So we got our pyruvate, the three carbon molecule, in animals it will undergo what we call lactic acid fermentation Okay, we're gonna go quickly over this. That basically means we're turning pyruvate, a three carbon molecule, into lactate, another three carbon molecule, by basically causing this to happen. Notice this is the exact opposite. Normally, right, these NAD, NAD+, wants to take electrons and hydrogens and get turned into NADH, but here it's the opposite.

NADH is going to drop off electrons and hydrogens and get turned into NAD. Okay, so this is very cool. And the key thing you need to take away from here is that you can see during anaerobic respiration in animals we can recycle this NAD plus Okay by turning NADH into NAD plus because this NAD plus is very important in glycolysis and the other steps to To take electrons and hydrogens, right?

We saw to form that ticket. So this is one way in which we can recycle um um nadh and turn it back into nad plus okay very cool so here's some words i'm not going to talk much about this because we talked about this in the sl video i just the extra thing we needed to add here was this guys it can be recycled okay now if you're a yeast something else happens you get turned into a two carbon molecule okay so remember here in animals it stayed three carbons this one is two carbons so we know there must be a step where we lose carbon and there is we lose carbon and again We don't lose it alone. We lose it in the form of carbon dioxide.

Okay, that's very important now the same thing as in Animals there is recycling so we turn nadh into nad plus so nadh is Oxidized it loses hydrogen and electrons. Okay, so pyruvate here is reduced because it gains hydrogen and electrons So again not going to talk much about that the key thing that's cool here Is you can see we're making a lot of carbon dioxide so bakers like to use um this is this is useful in baking because this can cause bread and stuff to rise okay that's why they like to add yeast into certain baking ingredients okay that's pretty cool and also you can make alcohol like this ethanol ethanol is um all alcohol that you can drink vodka wine whatever it contains ethanol all of them okay so ethanol is alcohol okay that's it very important now the last little bit can we talk now this right we talked about this whole thing now we got to talk about respiratory substrates. So this will be really really kind of quick, okay?

So we know, we just talked about glucose, but remember remember glucose is not the only thing that can be turned into ATP. We got other molecules and they will join this cycle in different stages. You don't need to know any detail, you just need to know that other respiratory, other substrates like lipids and amino acids can also be turned into ATP. Let me show you. So for example, there are some Other kinds of sugars besides glucose that can also undergo glycolysis and therefore kind of contribute to making ATP There are other things like amino acids and lipids look here lipids that can basically get broken down into acetyl-CoA Okay, which will therefore join the Krebs cycle, but they get turned into acetyl-CoA through some other mechanism not this mechanism Okay, but see they can also be used to make energy.

That's very important. So I'll put the words here amino acids Lipids sugars, okay, and then here there are some amino acids that even directly just join into the Krebs cycle Okay, so that's pretty cool So what I really want you to take away from this is that other things other? Macromolecules like amino acids like lipids can also contribute to ATP formation by inserting themselves into different stages Into him of cell respiration. Okay, and one multiple choice questionable question that they could ask you is which one, if I had to ask you one gram of sugar and one gram of a lipid, which one can make more ATP from cell respiration? The answer is lipid.

Okay. Not glucose. So lipids store more energy in the same mass as glucose does. Okay. And that's just because lipids, right?

They're made up of many carbons and basically the fatty acids can be broken down into many many little acetyl groups which can join Uh here in the krebs cycle. Okay, so lipids can also be a source of energy Don't go too crazy on this. It's just to kind of complete the cycle.

Don't get stuck on glucose other respiratory substrates do exist Okay, so I really hope that was useful. Let's do a couple quick questions before we end the video What which stage of cell respiration heals the most atp we know the last one right oxidative phosphorylation When one glucose molecule undergoes glycolysis, which of the following is formed? Okay, the answer is C.

Not 1 because there's a net production of 2 ATP. Okay, we make 4 and we use 2. So the net production is 2, not 4. So the answer here is 2 and 3. So it's gonna be C. Last one here. Which molecule is the final electron acceptor in aerobic respiration? We know it's gonna be oxygen guys.

Okay. So there was a lot, guys. We covered all of this stuff, but I hope it was useful.

I hope it made some sense and that the diagrams helped you out. And we will see you in the next one.

Transcript for:Understanding Cell Respiration Processes

Transcript for:
Understanding Cell Respiration Processes