 Okay, as I said, this is a walk through of the whole process and it's gonna be interactive and a little bit quiz-like. So I'm gonna ask some questions. I'm gonna ask you to label some stuff and go ahead and push pause when you need to to go through this process. This is an opportunity to study the whole thing from start to finish and check your understanding of how it is working. Okay, we are going to establish some places. First thing, what is the equation for cellular respiration? Go ahead and write that down somewhere and we're gonna attach it to this slide like and we're gonna keep it there. So hopefully you're like, dude, I know what that equation is and zoom in if you need to but the equation is glucose plus oxygen combines to form water and carbon dioxide and ATP. Something that's usually left out of the equation is that ATP doesn't come from the glucose molecule. You need ADP and P in order to get that ATP but the energy to build ATP from ADP plus P comes from that glucose molecule. Okay, another question. Where does cellular respiration take place? Well, this is a tricky one because we should have multiple answers Some of the processes take place in the cytoplasm of the cell a lot of them take place in the mitochondria. So what you see here is a piece of the mitochondria that we are going to, you can see I've color coded I've effectively color coded this part. We have places in here that match color wise but we're gonna be talking about mitochondria. Okay, let's label some structures. I've done a thing. Notice up at the top of the mitochondrion I took a square just like I did in the lecture earlier and this whole box, everything on your screen is showing you the, it's a snapshot of that one little square of the mitochondria. So let's label the parts. I want you to label the outer mitochondrial membrane the inner mitochondrial membrane, the intermembrane space the mitochondrial matrix and the cytoplasm. All five of those things should be labeled on the big blown up picture and the little mitochondria up in the corner. If you need some assistance, I've numbered them on the big mitochondria. If you still need some assistance, I've now correlated them with what's in the picture itself. Do you see all those? And I've given them the actual numbers. So you can see the outer mitochondrial membrane is that top line. The blue space is the intermembrane space. The mitochondrial matrix is green, number four, and the cytoplasm itself is white at the very top. I could flip this. We could take a different slice of mitochondrion and have different locations of all of our stuff. And that would be fine. So make sure you identify where you are when putting things in and labeling. I'm gonna go ahead and just label these for good so that you don't forget where we are and the context. But again, if I took a different slice of mitochondria and the relationships would all change. All right, some things that we need to keep track of. All the way through this, we're gonna do our energy accounting. And we're gonna fill in this table right here. We're gonna do a total energy accounting as we go. So we're not gonna break it down like we did in the previous lecture. But you fill this in, what are the things that we're gonna keep track of? Carbon dioxide is one. Oops, we're gonna do water and we're gonna do ATP and those high energy electron carriers. The reason why I left the high energy electron carriers to last is because I wanna just have a visual for how they work. Here's an electron carrier that's empty and of course you know I made it look like a little car. It can carry two high energy electrons. And this is how I'm making this visible to you. Anytime the high energy electron carrier gets rid of its electrons, the energy is going to be released. It's going to pass the electrons somewhere and energy will be released. And this is how I'm illustrating this. So you can see the energy that's released is squiggly lines. We can capture that and use that energy to do work. If those electrons get put back on the electron car, then we're just gonna refill that car. And in fact, the electron carrier is gonna go back and participate in the process again. It really is being recycled. The electron carriers are being recycled. Okay, let's see. Here's a question for you. What's the first stage of cellular respiration? What do you think? First stage is glycolysis and where, oh, I wonder if that's another question that I have. What is the input for glycolysis? What is the thing, what is going into glycolysis that we care about? Glucose and you can see how I've illustrated glucose in this diagram. What is the output for glycolysis? At the end of glycolysis, we end up with what? Two pyruvate molecules, very good. And you can see how I've illustrated the pyruvate molecules. What are some of the outcomes? Like what else comes off of this process that we wanna keep track of? ATP, how many ATPs do we end up with? I don't think I included them yet. And what's the other thing that we end up with that is relevant? We end up with two electron carriers. When we put, because we got two pyruvates out of this, let's go ahead and throw in those numbers into our energy accounting. Are you cool so far? We're processing right along. We go through the process of glycolysis and what you see now is everything that we got out of it. Two pyruvate molecules, two electron carriers and two ATPs. Could have added two electron carriers and two ATPs but it just felt busy. So we're keeping track of them down here in this electron energy accounting chart. Okay, let's see what happens to those molecules. ATP, where's it headed? It's headed off to be used. Where are the electron cars headed to the electron transport chain and where is the pyruvate headed to the mitochondrial matrix? Let's see when we arrive. Step two, we have to modify the pyruvate. So predict what's gonna happen with pyruvate. We're gonna take pyruvate, we're gonna produce acetyl-CoA. Remember, pyruvate has three carbons and acetyl-CoA has two. So what are, oh, hey look, what happened to the other carbon? We know what happens to the other carbon. It becomes carbon dioxide and this happens twice. So we end up with two carbon dioxides. Did you see we just added that into our energy accounting table? What else do we get out of this beautification process? Two high energy electron carriers. So now we have two more of those puppies which means we have a total of four high energy electron carriers. Where are the high energy electron carriers going? They're headed out, home kids. They're just going to the electron transport chain. Where is the carbon dioxide going? I answered my question, but I didn't see a way for you to know that I answered my question. Look, the carbon dioxide is being breathed out. And meanwhile, the acetyl-CoA is entering what? The citric acid cycle. Peace out to the electron carrier. Peace out to the two carbon dioxides. Now, citric acid cycle. Acetyl-CoA, remember we have two of those guys. Acetyl-CoA enters the citric acid cycle, goes through the whole giddy up and all we're doing is summarizing what's gonna come out. Carbon dioxides, how many of them come out? Cause we're done. We're gonna add the four remaining carbons are gonna get bumped out in the citric acid cycle. Keep track of that in our energy accounting and we have a total of six. What else do we get out of this process? I'm glad that I said ATP cause we get two of those guys and let's throw them into our energy accounting and make sure we keep track of that whole thing. So we get two ATPs out of this process. What else comes out? What's the big money maker? The electron carriers, the high energy electron carriers, they get loaded up. So remember I showed you the empty one? The empty one arrives at the citric acid cycle and says I'm here. I don't have any high energy electrons and all those molecules that are going through the chemical reaction cycling through that getting rid of all the carbons that came from the glucose, energy is captured in high energy electrons and given to that electron carrier. We load up eight of those guys. So we end up with eight more high energy electron carriers giving us a total of 12. Now we're going to send those electron carriers to the inter mitochondrial membrane and we're gonna go to the electron transport chain. Take a look at your carbon dioxide, there it is and your ATP, ATP again is heading off to be used. It's like, dude, we got money right now. Somebody's gotta spend it. Lots of places to spend it. It's gonna get used right up and carbon dioxide just gets breathed right on out. High energy electron carriers are headed to the electron transport chain. Notice how I made the visual look pretty much exactly like how I drew it in the previous version. When I drew it by hand, it just helps me to visualize these proteins that's sort of like passing something downhill and energy being released from that process. The high energy electron carriers, oh, we gotta add in our protons or our hydrogen ions and I'm starting us with not a gradient because we need those high energy electrons in order to establish the gradient. So the high energy electrons, ah, there they are. I went ahead and it looks like I said, let's pretend like it already happened and now we've got this high concentration of protons in that inner membrane space. So you aren't gonna be able to pump more protons into that space unless you provide an energy source, high energy electron carriers to the rescue. These guys are gonna pass off their electrons. Check out what happens. As they pass off those high energy electrons, energy is released, that energy is used. Look, here's a question for you. What will that energy be used for? That energy is used. Look, here's the proton that is being pumped by the protein into against its concentration gradient and into the inner membrane space. I have, that looks like another, okay, what do you think is gonna happen to the pair, the two pairs of electrons you see here? I don't know, what did I say? The electrons get passed to the next protein and a new high energy electron carrier shows up. As long as you can pass the electrons to the next protein and you can have another high energy electron carrier, we had 12 of those things, you can continue to pump. Now, if you look carefully, you'll see empty electron cars are headed back to the whole process to get refilled. They're gonna go back to the citric acid cycle and get more high energy electrons. More full high energy electron carriers are gonna show up and be ready to pass off more electrons. Meanwhile, the energy is being used to pump protons against the concentration gradient. So look, we're just gonna continue this process. Notice how this is happening. We continue it. We keep it going. It's still happening. Okay, what has occurred now? Well, do we have anywhere to pass our electrons? Not yet. The question prompts us for what we wanna think about next, which is, okay, we just created a high concentration of hydrogen ions in this intermembrane space. What can we do with that? We gotta do something with that. And this is where we let the hydrogen ions out. So notice I've highlighted one of our hydrogen ions. I'm also bringing in who? One of the hydrogen ions is gonna get out. And as long as we have ADP plus P coming into the ATP synthase, voila! We're gonna turn the ADP plus P into ATP using the energy that came through down that hydrogen ion concentration gradient. It's true. That's happening in you right now. Off goes the ATP. Notice we grabbed another hydrogen ion. This guy's gonna come down. Another ADP plus P is making its appearance. Another ATP is generated. It bounces another, we can continue for forever. We could continue that forever. As long as we have a hydrogen ion concentration gradient, ATP synthase is gonna keep going. In order to have that, we have to keep pumping protons because they're gonna leak out through that ATP synthase and our concentration gradient's gonna go away and then we're not gonna have anything left. So what do we have to do? This could be quite possibly the most important part of the whole story. You have to have somewhere. You have to be able to keep pumping hydrogen ions, which means you have to get rid of these two electrons. You have to have somewhere to put them. Where do we put them again? Well, we gotta have a final electron acceptor. Dun-dun-dun-ah, who has arrived to the scene. Oxygen, oxygen is your final electron acceptor. Check out how I'm adding in a couple of protons. There's gajillions of those clowns. I'm adding the electrons. There's, we want, that's the whole point. We've got these electrons. We gotta put them somewhere. And now we're gonna end up with water. We actually, the math is not going to math on this unless we add up a bunch of hydrogen ions and a bunch of electrons and that's fine. Bottom line is that oxygen serves as that final electron acceptor and does turn into water. Water, we'll take that all day and water just disappears and it just becomes more of cell soup and is awesome. How many water molecules do you think we'll get from one glucose molecule? Six, balance your chemical equation and we know that we're gonna have to have six water molecules and it's true. Ultimately that glucose molecule produces six water molecules. Okay, shall we review the whole thing? Watch the whole thing in action, the whole electron transport chain in action. I'm showing you the whole chain, the whole process so that you can see all the pieces that are coming through at the same time. Electron carriers are coming to give new electrons. Water is arriving to, I mean oxygen is arriving to accept those electrons. That allows more electrons to be passed which allows those proteins to pump more protons which allows the proton gradient to exist so ATP synthase can produce more ATP. I do not know how long this goes but how cool is it that we just keep going and going and going and going. More water, more water, oh, enough. We've had enough of this. So if that is helpful, I'm very glad. If it's not helpful, I hope you skipped it. I guess if you're still here it was helpful to you and it's a great way to practice and test yourself to make sure that you can visualize how all the processes work together. Okay, two things left to talk about.