 Where do we get the energy to do this? Where do we get the energy to take ADP and rip a phosphate off of a water molecule and push them together to produce ATP? Where does the energy come from? Dogs, we're talking about cellular respiration. It must come from glucose. In fact, does this work for you? The whole point of this whole thing is we're going to take a glucose molecule, C6H12O6, and we're going to send it through this process of cellular respiration, and our whole goal is to get energy out. How? We have to break apart the molecules in the glucose. We have to break apart those atoms, break those bonds, and form new bonds and use the energy in that process to put a phosphate onto an ATP molecule. Allow me, I mean an ADP molecule to make an ATP molecule. Let me show you how it's done. There are three main stages in this process that we're going to look at, and the first one is called glycolysis. And glycolysis takes place in the cytoplasm. Does it take place in the mitochondria? No, it takes place in the cytoplasm. Glycolysis is basically taking a molecule of glucose and breaking it down into a molecule called pyruvate. And we actually get two of them out of this process. In addition to getting pyruvate, breaking it apart and getting pyruvate. And there's, oh, it's crazy. The number of intermediate steps that we're not even going to look at. In fact, I've got it, I've got to show it to you so that you can appreciate the fact that, yeah, right? This is happening, here's my mitochondria. It's happening in the cytoplasm so it's outside of the mitochondria. But look, we start out with glucose, serious. So kinase turns it into glucose-6-phosphate, which then phosphoglucosisomerase turns it into fructose-6-phosphate. I mean, how many steps are there here in this whole process? And then we end up with, oh, check it out, pyruvate. I am going to take this whole process and summarize it for you so that you do not have to memorize each one of those stages. The molecule, the enzyme that catalyzes the reaction and any possible byproducts. We're just going to summarize the whole thing. But please don't forget that that's actually what is happening. It's a crazy set of chemical reactions. Out of this process, we're going to get two important, we're going to keep track of two important substances. First of all, obviously, we're going to keep track of ATP and there are two ATP molecules that are formed in this process. But what did I make green? Do you remember? We actually have two electron carriers, high-energy electron carriers. We can call it an electron car. Two high-energy electron carriers are produced and you will see why we even are keeping track of those and two molecules of ATP. Pyruvate is not the end game. In fact, pyruvate by itself can't move on to the next stage. So we have to go through a process of fixing pyruvate. So we're going to turn pyruvate into a molecule called acetyl-CoA. We're going to see, dude, seriously, acetyl-CoA. And there's a couple of things that we want to keep track of here. First of all, coming off of this process of turning the molecule into acetyl-CoA, we get two carbon dioxides that come out of this process. That's relevant. This is your whole cellular respiration equation. One of the products of the whole equation was carbon dioxide. Well, here's where two of our carbon dioxide molecules come from. In addition to that, we actually get two more what? Two more electron carriers. Did we get any more ATPs? No, but we did get two more electron carriers. So at the end of glycolysis, we end up with acetyl-CoA, which is ready to go into the next process. And we have two molecules of ATP and a total of four electron carriers. Plus, we've actually gotten some of the carbon dioxide that is released in the whole process. Yeah, yeah, yeah. Is that good? Let's move on and let's take a look at the citric acid cycle because acetyl-CoA is the buddy boy or girl, however you want to think about it. Acetyl-CoA is going to enter the citric acid cycle.