[BLANK_AUDIO]. So cellular respiration. Steph, you talked about glycolysis, I think, yeah? So glycolysis is the first stage of cellular respiration, right? So we go through this process of glycolysis. And then the second stage of cellular respiration is, what? Who knows? Andre? >> Is it the Krebs cycle? >> Exactly! The Krebs cycle, yes. And the Krebs cycle continues this metabolism of our fuel molecules, right? And after the Krebs cycle, what's the next stage of cellular respiration? Yeah. >> Oxidative phosphorylation. >> Oxidative phosphorylation, exactly. That is a very long word and fortunately we do not have to get into the process in great detail, right? The term is enough to turn us off, right? But we only will deal with the big concepts here. Okay, so we start with glycolysis. And we have this picture open in front of us, that is going to show us a little bit about what's happening with the decomposition of cellular fuels during the stages of cellular respiration. And if we look, what we see is that Glucose, and other simple sugars. Get kind of channelled into the glycolysis pathway, right? And there those simple sugars get broken down, glucose specifically gets broken down in glycolysis to something called pyruvic acid, right? And if we look at what happens then, pyruvicacid gets further, you know, converted and ultimately will be channeled into the Krebs cycle, right? So you see the Krebs cycle pictured here for you. And at the end of the Krebs' cycle we are left with molecules that can get channeled into the oxidative phosphorylation pathway. And all along these pathways, what is happening is that ATP is being generated, okay? Glycolysis takes place in the cytoplasma of the cell. The Krebs cycle and oxidative phosphorylation involved in mitochondria right. And I think that this set of three stages forms the backbone for the cellular metabolism. So to have those in mind all the time as you're thinking about what's going on with fuels in the body, this is the backbone. Now, let's look at what happens to amino acids. Notice that, you know we could use excess amino acids to make ATP too. And basically we would do that by channelling the amino acid products into one stage or another of cellular respiration, right. So where do proteins get channeled into, the metabolic pathways. You see 'em getting channeled in, Mia? >> It goes into glycolysis? >> Yes. >> And then it will combine with pyruvic acid. W-, well, it, i-, it can get channeled into the glycolysis pathway, right? And it can also, you know, be converted to that kind of, intermediate molecule, acetyl CoA. >> Mm-hm. >> It can be channeled into the metabolic pathway, there. Or, you can see infrequently, the Krebs cycle, yeah. So, normally our body would use amino acids anabolically to build new protein. But if there is an excess of amino acids or if if we maybe are just starving. Your body can actually break down its own proteins, into amino acids, and then those amino acids can also be used as a fuel, right? But normally we would just use amino acids to build new proteins in the body. Now what about fats, or the lipids? Our main dietary lipid is triglycerides, right? And so those are the lipids that we talked about being broken down into monoglycerol and fatty acids during digestion. Then we absorb them, and the body uses them as, triglycerides. But notice, if we're going to break them down and use them as a fuel. What do we do? We break triglycerides into glycerol and fatty acids, right? And then how do we metabolize them in cellular respiration? How do they enter the pathway? Steph? >> The monoglycerol can be put into the glycolysis cycle? >> Glycerol can go into glycolysis, exactly. Mm-hm. >> And the fatty acid will go into acetyl-CoA? >> Mm-hm, and then get channeled into the Krebs Cycle, exactly. So we can also use excess fats as, or any fats as a fuel. Cool. [BLANK_AUDIO]