Look at the eight steps of the citric acid cycle (Figure 21.8) and answer the following questions:
b. Which steps involve decarboxylation (loss of CO₂)?

Question

Look at the eight steps of the citric acid cycle (Figure 21.8) and answer the following questions:

b. Which steps involve decarboxylation (loss of CO₂)?

Accepted Answer

Hi, everybody. Let's look at our next question here. Which step or steps in a citric acid cycle lead to the production of carbon dioxide A steps 346 and eight B steps five and seven C step one or D steps three and four. So I'm going to post up a little overview of the citric acid cycle. But let's kind of think through some of the things that we might think about when looking at a question like this on a test. I do think it's important to be, you know, have sort of a basic diagram. Maybe you sketch for yourself when you have a question like this to keep things straight. But there's things we can do to kind of zoom in on the possibilities. So production of co two would happen when the molecule that's reacting in the cycle loses a carbon atom. So we know that we have a seal coa entering the cycle with two carbons. It combines with four carbon oxy acetate to make six carbon citrate in step one. So we can rule out step one because this is a combination of two different molecules to make a six carbon molecule. Now, this step involves combining to increase, not lose carbon atoms, you're not going to be seeing a carbon dioxide released there. Second of all, since we know being a cycle, we're going to regenerate our poor carbon oxy acid at the end, that means we only will lose two carbon dioxide molecules or produce two carbon dioxide molecules because we only lose two carbon atoms. Acetyl coa enters the cycle with two carbons. So two carbon dioxide molecules are going to be released. So we'd only expect either one or two steps because I don't know if a step produced two carbon dioxides. But that would be quite unlikely even if we didn't remember for sure. So we'd expect our answer to have two steps. So we can eliminate choice a steps 346 and eight, we're not going to produce four carbon dioxide molecules. So we right, too many steps. So we can expect our answer to be choice B steps five and seven or choice D steps three and four. And again, if we want to just think logically, um if we have sort of an overall general map of this process in your head, there's eight steps in total. So if we think of that circle there, steps three and four will be on the right at the beginning of the process, steps five and seven on the left. And hopefully we remember that those carbon dioxide molecules are released towards the beginning of the cycle. So just by using logic, we can get our answer of choice D steps three and four and no steps five and seven. But now that's talking how I might approach this on a test that couldn't remember my cycle really clearly. But hopefully you do, I'm going to post up a diagram of the cycle and we'll just touch on this a little more thoroughly since this is a practice problem. So I have a little diagram here. The, the sorry, the citric acid cycle, uh it doesn't have the steps numbered, but we can look at that. So we start here with acetyl coa at the top. And I will highlight where we see these two carbon dioxides being produced over on the right side as we said. And if we number our steps, we see that these are steps three and four as we figure they logically must be. So in these steps in step three, I didn't write on here because the step two is an isomerization reaction from citrate to isocitrate. Then step three is that conversion of isocitrate to alpha ketoglutarate. It's an oxidation reaction. So we produce a molecule of N A DH along with a molecule of carbon dioxide. Since we're going from the six carbon crate to the five carbon alpha ketoglutarate. And then on our next step, step four, alpha ketoglutarate is being converted to succinyl coa. It's another oxidation reaction. One molecule of N A DH is produced as well as that molecule of carbon dioxide. And we go from five carbons to four carbons. So there are the two carbons that are lost. We're now at a four carbon molecule and it will remain four carbons all the way back until regenerating that four car carbon oxy acetate. So in the citric acid cycle, the steps that lead to the production of carbon dioxide are choice D steps three and four. See you in the next video.

Look at the eight steps of the citric acid cycle (Figure 21.8) and answer the following questions:
b. Which steps involve decarboxylation (loss of CO₂)?

Verified video answer for a similar problem:

Key Concepts

Citric Acid Cycle

Decarboxylation

Enzymatic Reactions

Look at the eight steps of the citric acid cycle (Figure 21.8) and answer the following questions:b. Which steps involve decarboxylation (loss of CO2)?

Verified video answer for a similar problem:

Key Concepts

Citric Acid Cycle

Decarboxylation

Enzymatic Reactions

Look at the eight steps of the citric acid cycle (Figure 21.8) and answer the following questions:
b. Which steps involve decarboxylation (loss of CO₂)?