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0:05
>> Cellular respiration. If you are anything like me, you have had people teach you or try to teach you Cellular Respiration about a million times and you just don't want to learn it and retain it. What I'm going to do before I start teaching you a little bit in detail. By the way, we're not going to go into as much detail in physiology as you would in biochemistry for cellular respiration. We're going to look at the big picture and apply it to human physiology.
0:36
What I'm going to do before I get into the weeds of cellular respiration, I want to convince you that it is worth your time to learn. It's never going to leave us this whole semester. You need to have a working understanding of cellular respiration. This picture that you're looking at right here is really an overview. It's a super simplified overview, although it looks very complex of cellular respiration of the three macromolecules. You can do cellular respiration of amino acids and get ATP.
1:07
You can do cellular respiration of carbohydrates and get ATP. You can do cellular respiration of lipids and get ATP. But what I'm going to focus on first and then I'll contrast the other things with it is cellular respiration of the molecule that the brain and everything else can burn relatively well which is glucose, which is a large organic molecule. You probably remember that it's C_6H_12O_6. What you are going to do is you're going to break it down to smaller things like
1:39
carbon dioxide and water and you are going to generate ATP as a byproduct. That's the whole point. You're taking large organic molecules, you're breaking them down to smaller things and you're generating ATP as a product. Question? Before I tell you the equation that you are going to learn for cellular respiration, is this that I just described to you. Taking glucose and breaking it down to carbon dioxide and water and generating ATP as a byproduct. Is that a catabolic or anabolic process?
2:12
What do you think? Catabolic or anabolic process? It is catabolic. We're going to use this ATP for whatever the hell we want to move to wiggle, to make proteins, to do whatever the hell we want. Before we get into it, I want to show you the big-picture understanding. You're going to write it right here of the summary of cellular respiration. It's going to be even a little more simple than this. Some of this is going to be important to you.
2:43
This is definitely more simple than what cellular respiration really looks like. Really glycolysis, that purple box looks like that. The linking reaction Krebs cycle looks like this.
3:04
Then electron transport looks like that or oxidative phosphorylation. We're going to learn it in a lot more simple terms because I really want you to be able to see the forest and not just the individual trees. Before we get into the details, let me introduce you to the summary equation of cellular respiration and try to convince you that you care about it. Big picture understanding of cellular respiration. What cellular respiration is really doing, is it's taking a big organic molecule?
3:39
And I'm going to use glucose because it's the brain's favorite and everybody likes glucose. Most of you guys actually already know the equation for glucose, which is C_6H_12O_6. In the presence of oxygen. This arrow represents boatloads of arrows. It actually represents glycolysis, cellular respiration, and oxidative phosphorylation. That arrow is actually a bunch of arrows. But if I'm looking just at what comes in, the reactants and the end products.
4:12
What I will end up getting is carbon dioxide, water, and ATP. You don't have to keep track of the NAD, the NADPHs all that crap for me. You need to keep track of this big one right here, which is super important, which is the ATP. You don't have to balance the equation for me, you will have to keep track of some numbers of ATP and where it's generated. But you don't have to balance the equation for me. Let me convince you that this equation is worth you
4:47
memorizing because I want to try to convince you that this equation is the entire reason that you eat and the entire reason that you breathe. You eat because you need to generate or you need to ingest large organic molecules. You are not a plant. You cannot make your own glucose. Plants can make their own glucose and then burn their own glucose to make their own ATP, which is arguably cooler than animals. You eat because you need this,
5:22
you breathe because you need this in and you need to get rid of this. Carbon dioxide, when it builds up, it will start to change your pH and change the shape of your protein. This is not much of a problem. This is called metabolic water, and in most circumstances, it just blends with the water that you have, which is around 60% of you anyway. This equation is called aerobic because it uses oxygen. Aerobic cellular because that's where it occurs and respiration.
6:03
Now I will tell you that it was an embarrassingly long time before I figured out that this was actually called respiration. Because at the cellular level, it's oxygen in and carbon dioxide out. Some of you guys probably figured out the first time you were taught it in seventh grade, but I was not that person. Cellular respiration is what this is called. What we're going to do as we go through and learn these little parts of cellular respiration, the glycolysis, Krebs, and Oxphos.
6:35
We're going to keep track of where this is used, where this is used, where this is used where this is generated, where this is generated and where this is generated and it's not going to be that bad because we're not going to balance it. Really the only thing that we need to keep track of as far as numbers is the ATP. Big picture understanding. Basically what we're saying is that equation is glucose and they don't show you oxygen in until right here, but it actually goes in this area as well.
7:09
Glucose plus oxygen equals carbon dioxide, water, and ATP. Then we'll just keep track of where these things come out, where oxygen is required. It's not going to be as bad as you think it is. The first stage of cellular respiration is glycolysis, which I said, actually looks like this. We can just learn it as this magical purple box. Glycolysis, the name implies what it does. It takes the sugar, a glyco, and lysis it, which is breaks it down.
7:42
This is where carbohydrates are going to start their breakdown. Plus one little fatty weird thing called glycerol. As soon as you get a carb small enough, like a monosaccharide or disaccharide. It can go through glycolysis. Glycolysis is really old. It's actually older than mitochondria, it's actually older than animal cells. It occurs in bacteria.
8:09
It doesn't actually need oxygen because it actually predates oxygen in high levels on this planet and it doesn't need mitochondria. It actually predates mitochondria as well. It occurs in the cytoplasm or the cytosol. Even though you memorized that the mitochondria is the powerhouse of the cell. You actually make a little bit of ATP before you even get it in the mitochondria and that's in glycolysis. What happens to this intermediate product called pyruvate? Well, if oxygen is present,
8:39
you can continue going down.Notice you're going to start giving off things that have oxygen on this side. Oxygen is required right here and right here and right here, even though they only show it right there. If oxygen is present, you keep going. Why do you care if you keep going? Because this is a pitly amount of ATP. This is a pitly amount of ATP, but this is a bunch of ATP. If oxygen is present, you're going to keep going into Krebs, and Oxphos. If oxygen is not present, however,
9:13
you generate relatively little ATP. One round through glycolysis from one molecule of glucose generates two ATPs net, it actually generates four and uses two, there's two left over. It requires two ATP, it produces four ATP. It's a net gain of two ATPs. Not very impressive at all. Now let's go back to our figure for just a second and start keeping track of where things are going to be used and where things are going to be generated. Under each reactant and product,
9:46
what I want to do is keep track of where they were used. Did I use glucose right here in glycolysis? Yes. That's where we used it. Glycolysis. Did I use oxygen in glycolysis? No, I didn't use oxygen. Did I generate carbon dioxide? No, I couldn't because I didn't have any oxygen yet. Did it generate water? No, same reason. Did I generate ATP? Yes, I actually generated ATP, I generated two in glycolysis. I'm keeping track. I've still got to take care of all of the rest of the things before I get
10:26
finished accounting for everything in my equation. Now let's look at the next part. The next part is the linking reaction and Krebs. I'm going to lump those two together. The linking reaction actually does this. Then Krebs does this. It actually does it twice. Eight enzyme-catalyzed reactions twice. Again, Krebs actually looks like this, but that's fine. We can just look at it like this. If you are a carb and you go through glycolysis and had oxygen, you would go through Krebs.
11:01
This is where carbohydrates continue their breakdown. Notice that when we get into this a little bit later, if you're a fatty acid, sometimes you can go straight before Krebs. If you're a protein or an amino acid you might go into Krebs. We'll worry about that later. Right now we're following straight down. This is where carbs continue their breakdown. It occurs in the mitochondria. Everything that occurs in the mitochondria requires oxygen. Once again, although they didn't tell you before,
11:34
I wish they had I wish they had said let me use the purple that they use there. >> I wish that they had said basically O_2 is required here as well, so after glycolysis, oxygen is pretty much required.
11:58
Occurs in the mitochondria, it requires oxygen, the other way of saying that is that is aerobic. How much ATP is formed from Krebs? I'm going to just hedge and say about two, because there's a couple of different pathways that you can go down depending on what you started with and what you've got, and it can produce 0-2 ATPs. Either way, it's not a very impressive amount of ATP. Importantly, look at what we are seeing, starting to see produced as a byproduct carbon dioxide.
12:32
Carbon dioxide is produced in linking and Krebs and a little ATP is produced as well, which means we need to go back to our drawing.
12:44
I accidentally lost it so it's okay because I know the equation, I can rewrite it.
12:59
I do know the equation I'm just being a dingbat,
13:04
C_6H_12O_6 plus O_2 yields CO_2 plus H2O plus ATP. We're just going to read what I did before. Same question I asked before, did I use any glucose and glycolysis? The answer is yes, I used it in glycolysis. But I didn't use any oxygen in glycolysis to degenerate any carbon dioxide or water and glycolysis, no. But in glycolysis, I did for the first time generate ATP and I generated two in glycolysis. Now do not erase the board next time Melanie.
13:48
Next question, so we just went through linking in Krebs. Same question, did I use any more actual glucose? No, I didn't use anymore, I'm still working on the one that I tried, so I didn't add any more glucose. Did I, however, use oxygen? Yes. For the first time, I'm just going to say Krebs to mean linking and Krebs. I did use oxygen so for the first time I used oxygen. Did I generate any carbon dioxide? Yes. Linking and Krebs is where carbon dioxide is generated.
14:30
Did I generate any water? I didn't, If you don't remember we look back at the diagram in just a second. Did I generate any ATP? And probably, yes. I generated between 0-2 and that was in Krebs. I won't erase this the next time. Last thing is OXPHOS, oxidative phosphorylation, also called electron transport, really looks like this. But we're not going to do it that way we're going to look at it like this, which is just this yellow box. That's fine not hard at all it is hard,
15:09
but we're not going to do the hard part. If I'm a carb and I still have oxygen, I can continue break down here.
15:19
It uses the combined products of glycolysis and Krebs. It is aerobic, it requires oxygen, and look what it generates as a by-product. I don't know if you'd notice that water was not generated by linking and Krebs, it's generated down here, produces water as a by-product. Here's the really important thing, it produces 34 ATPs per molecule of glucose. Now, before we just farting around and producing two or 0-2, but now what we have is 34 ATPs. This whole process with a single molecule of
15:58
glucose one time through produces around 36-38. Different textbooks will go one way or the other, but far more than two or four, from a single molecule of glucose, if oxygen is present. If oxygen wasn't present, how much ATP would I have generated from one molecule of glucose one time through? I would have generated two. Oxygen is really important in getting the most ATP out of your food molecules. In the absence of oxygen, you cannot break them down and get much ATP out of them.
16:30
The whole process produces 36-38 ATPs from a single molecule of glucose if oxygen is present. You should be able to write the unbalanced summary equation that we've been working on in the board, I'm about to go back to for aerobic cellular respiration. Then you're going to need to account for all of the reactants are used in all of the products are generated, but just the summary, not all of the intermediate products. Let's go back and fill out the very last part of this.
16:58
Filling out the very last part of this, I'm going to ask the same blasted questions that I asked before, which is, am I going to use any more glucose? No, I'm not. I'm still working on the glucose from before. Am I going to use any more oxygen? Definitely. OXPHOS, hence the name oxidative phosphorylation uses oxygen. Am I going to generate any more carbon dioxide? You may not have noticed from the figure, but you don't generate any more carbon dioxide. But do you generate water?
17:34
Yes, you actually generate water. You generate water in oxidative phosphorylation. That's where it comes from. Very importantly, do you generate any more ATP? Yeah, you generate [inaudible] ATP. You generate 34, usually ATPs from OXPHOS, which will get us a total. From one time through aerobic cellular respiration with one molecule of glucose, what is the total amount of ATPs that you can generate using this math that we've used? It is 36-38 ATPs.
18:19
That's impressive compared to the two that we could have generated without.
18:27
Cellular respiration and having the ATP to run your cellular processes could not be more important for physiology. Then, of course, to bring this back home, I want you to understand that I'm doing a lot of figuring out what to do with this carbon dioxide. For instance, what happens in a cell if you don't have adequate amount of oxygen? What happens in a cell if, for instance, you can't get glucose like in a diabetic situation? This big picture understanding is going
19:00
to be really important for the rest of the semester. You definitely need to be able to write the unbalanced summary equation, what I just wrote on the board for aerobic cellular respiration. Then you have to know where the big players are involved. Which parts? Glycolysis, Krebs, or OXPHOS. That is how we are going to approach cellular respiration and physiology. I'm going to reinforce it all semester long, so I promise this isn't something that I'm going to teach you and then throw away.
19:37
In physiology, if you don't know the answer, guess homeostasis or cellular respiration because you're probably right. If you've never committed this from memory before, what I'm going to need you to do is try to do that now. One of the ways that I'm going to do it is on your first exam. One of your essay questions is going to be to give me in four sentences or fewer an application of cellular respiration to human physiology. Application is not you would die without it, it is,
20:09
for instance, taking one of these players and figuring out how it occurs. Like what do you use ATP for? Give me a specific physiological example. What do you have to do with the carbon dioxide? Give me a specific physiological example. What if you couldn't get glucose into the cell? All you are going to do is you are going to noodle around on that until you get to your first exam. Stop there for today.
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