The glycerol derived from lipolysis of triacylglycerols is converted into glyceraldehyde 3-phosphate, which then enters into step 6 of the glycolysis pathway. What further transformations are necessary to convert glyceraldehyde 3-phosphate into pyruvate?

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Hello everyone. And welcome back. Our next question says is the following statement, correct. The glycerol obtained from the breakdown of tri ay glycerol through lipolysis is converted into glyceraldehyde three phosphate, which then enters the glycolysis pathway at step six, it is converted into pyruvate after two additional steps. A the following statement is correct. B the following statement is incorrect. So we have a couple elements of our statement and we need to make sure they're all correct. So they are, the glycerol is converted into Glycerol to Hyde three phosphate. The glyceraldehyde three phosphate enters the glycolysis pathway at step six. And then G the glyceraldehyde three phosphate is converted into pyro after two additional steps. Well, there's a bit of a shortcut to the answer here because looking at number three, that's the easiest one to evaluate when we think about glycolysis. One of the overall facts that we should know is that glycolysis is a 10 step process that converts glucose into pyruvate. So if our glyceraldehyde three phosphate enter the glycolysis path mate step six and then says it is converted into pyruvate after two additional steps. Well, that couldn't be possible because it takes 10 steps to get all the way to pyruvate. If it is entered at step six, there must be four additional steps to get all the way to pate. So right away, we know that this statement must be incorrect. If I had this statement, if I had this question on a test notice that it doesn't ask me to correct the statement, it just says, is it correct or incorrect? So I would circle choice B it's incorrect and move on. Now, this is a practice problem. So we'll be a little more thorough here and talk about why this is incorrect. And then what we need to do is just double check is part one correct is a Glycerol converted into Glycerol hyd three phosphate. And that is correct. So indeed, when we break down tri ao glycerol, so we'll say tag or triglycerides, they get broken down into their components, the fatty acid chains, which then go on to the process of beta oxidation and then the Glycerol backbone. And that Glycerol is indeed converted into glyceraldehyde three phosphate. And this process happens in three steps. First, Glycerol is phosphorated, um using a TP to form Glycerol three phosphate that is an oxidized to form DH A P or dihydroxy acetone phosphate. And at this point, you probably recognize something from the glycolysis process. And then in conjunction with, you know, in a similar in the same way as in step five of glycolysis, the DH A P is is summarized to form glyceraldehyde three phosphate. So that step there is step five of glycolysis. So then we can see that our product of glyceraldehyde three phosphate is ready to enter the glycolysis pathway at step six. And then, as we discussed, here's where our statement becomes incorrect. So we do indeed enter glycolysis in step six. But then it takes four additional steps to convert glyceraldehyde three phosphate to pyruvate. So that would be step seven or then I should backtrack a little bit to remind you that in step six, our glyceraldehyde three phosphate becomes bis phospho glycate or BPG. And then step seven that gets converted into three phospho glycate generating a molecule of a TP as we lose one of those phosphate groups in step eight, that gets isomerize to two phospho glycate. And then in step nine, we generate phospho phosphoenolpyruvate, which then in step 10 becomes pyruvate along with a TP as you lose another phosphate group. So we do indeed have an incorrect statement. So our answer is choice B the following statement is incorrect because although the, it is correct to say that the glycerol is converted into Glycerol three phosphate, which enters the glycolysis pathway. At step six, it takes four additional steps not due to convert this into pyruvate. See you in the next problem

The glycerol derived from lipolysis of triacylglycerols is converted into glyceraldehyde 3-phosphate, which then enters into step 6 of the glycolysis pathway. What further transformations are necessary to convert glyceraldehyde 3-phosphate into pyruvate?

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Key Concepts

Glycolysis

Glyceraldehyde 3-Phosphate Dehydrogenase

Substrate-Level Phosphorylation