Citric Acid Cycle Practice 2 - Video Tutorials & Practice Problems
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Citric Acid Cycle Practice 2
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If you haven't completed the questions, pause the video now and give them a try. The conversion of 1 mole of Acetyl CoA to 2 moles of CO2 results in the production of 1 mole of FADH Now, in each turn of the citric acid cycle, you'll use 1 acetyl CoA and you'll produce 2 CO2 as the problem said but you're also going to make 1 FADH2, 3 NADH, and one GTP which can be converted to ATP but won't necessarily be. So that is why the rest of the answer choices are wrong. This should be 3. This should be GTP. It should be 1. And citrate is or whoops rather it's only 1 mole of citrate that's going to be produced. But it's, of course going to be used up too. That's why I was crossing out. It's not really like a product, you know. You will generate citrate in the process but it's not like a product. It's just part of the cycle. Anyways, question 7, the reaction in the citric acid cycle most similar to pyruvate dehydrogenase converts alpha ketoglutarate to succinyl CoA and that is carried out by alphaketoglutarate or AKG. I'm going to abbreviate it. Dehydrogenase. Now, this reaction is also carried out by dehydrogenase. This is isocitrate Now, the, the difference is or not the difference. The isocitrate, this doesn't use the same cofactors and substrates as pyruvate dehydrogenase. Whereas there are some similarities. I mean it does generate NADH but the buck stops there. With alpha ketoglutarate dehydrogenase, you're using TPP, lipoate, and oops. F a d. Let me jump out of the image here. You are also using NAD+ and CoA. So there's a lot of similarities between pyruvate dehydrogenase and alpha ketoglutarate dehydrogenase. The reaction in the citric acid cycle that produces GTP is the one that converts produces GTP is the one that converts succinyl CoA into succinate because remember, it's breaking that thioester bond that provides the energy for the substrate level phosphorylation to convert GDP and inorganic phosphate into GTP. Of course, as we've already said, that GTP can be used to make ATP, but it won't necessarily be used for that purpose. Now, which citric acid cycle intermediate is considered prochiral? Well, what's prochiral? Prochiral means that the molecule is not actually chiral but it's going to behave like it's chiral. The answer is citrate. You might remember that citrate is a symmetric molecule but aconitase will actually interact with citrate as if citrate were chiral. Now, just looking at these choices, I also want to point out that succinate is, also a symmetric molecule but it is not prokyl, right? It can be randomized in its orientation in, succinate dehydrogenase. Now, the conversion of 1 mole of pyruvate to 3 moles of carbon dioxide by pyruvate dehydrogenase and the citric acid cycle will produce 4 moles of NADH. Right? One from pyruvate oxidation. Pyox. 3 from the citric acid cycle. It'll produce 1 mole of FADH also from the citric acid cycle and it will produce 1 mole of ATP again from the citric acid cycles. The answer is d. Now, the glyoxylate cycle is not something that we talked about but it is something you need to know about for the exam. And this is something that is carried out by, not by humans but by plants, fungi, bacteria and what this does is it uses Acetyl CoA for energy and the synthesis of biosynthetic precursors. So, if you recall, we cannot convert Acetyl CoA back into sugar, right? Well, plants can. That's basically the story here, you know. They and and they can use the acetyl CoA for other things too but but they can, they can through the glyoxylate cycle, page.