Hey, everyone. So when it comes to the pyruvate oxidation, recall that one glucose is converted into 2 pyruvate molecules through the glycolysis pathway. Remember this pathway here is linear in nature, and we're going to say the fate of the pyruvate depends on the availability of oxygen in the cells. So if we take a look here at the steps or stages of food catabolism, and we're paying attention to the monosaccharides in this case. We'll talk about amino acids and fatty acids in later sections. But for now, we have our monosaccharides that go into the cytosol, and this is where glycolysis takes place. Now remember, glycolysis here will create NADH as an energetic molecule, as well as ATP. In addition to this, we're going to make our pyruvate molecule within stage 2. That pyruvate could take one of 2 directions. If there is no oxygen available, then it would go towards fermentation where we have anaerobic respiration. We'll talk about that later on. Now, if oxygen is present, then it continues forward into the acetyl CoA formation. This then takes us into the mitochondrial matrix where we're dealing with stages 3, which deals with the Krebs cycle or citric acid cycle. And then from there into stage 4, where we're dealing with the ETC and oxidative phosphorylation for the generation of ATP molecules. So, just remember, this section here is called our common metabolic pathway, and it's in this portion where oxygen is available and so we're dealing with aerobic respiration. So just remember, pyruvate can do one of 2 things based on the availability of oxygen.
Pyruvate Oxidation - Online Tutor, Practice Problems & Exam Prep
Pyruvate Oxidation Concept 1
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Pyruvate Oxidation Concept 2
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Now, remember the fate of pyruvate is based on the availability of oxygen. When oxygen is available, we undergo aerobic respiration. In the presence of oxygen, pyruvate is transported from the cytosol to the mitochondrial matrix. Here, pyruvate is oxidized by pyruvate dehydrogenase to Acetyl CoA. Remember, when it comes to our oxidation reactions, the class of enzymes that we utilize are the dehydrogenases. That's why it's called pyruvate dehydrogenase. It's the substrate name followed by dehydrogenase. In this process, one NAD+ is reduced to one NADH. We're going to say here that one carbon is lost as carbon dioxide.
If we take a look at our reaction, we have our pyruvate molecule here. We've highlighted the carboxyl group of this pyruvate molecule. We have coenzyme A with its thiol group, and we have NAD+. Here, we would lose carbon dioxide and have the generation of NADH. This would be helped by enzyme pyruvate dehydrogenase. In this process, we oxidize to become our Acetyl CoA molecule. So just remember, this happens under aerobic respiration, which can only occur when there's oxygen available.