Glycerol Metabolism - Video Tutorials & Practice Problems
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Glycerol Metabolism Concept 1
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Now, when it comes to Glycerol metabolism, we're gonna say the main purpose is a TP production through glycolysis. And we're gonna say a secondary function is energy storage through gluconeogenesis. If we take a look here at Glycerol metabolism, we have the digestion of our lipids that can break down into glycerol and fatty acids. But here we're looking at Glycerol itself. Here, Glycerol metabolism would convert that into DH A P. This DH A P could enter glycolysis and become pyruvate. Now, here we're not concerned with stage three or stage four when it comes to food metabolism. So we're gonna ignore that. But when it comes to these two, DH A P and pyruvate, they themselves could be routed within stage two within the cytosol to create glucose. So just remember, besides the main function of A TP production through glycolysis where we make pyruvate, which then can go into the citric acid cycle and then electron transport chain and oxidated phosphorylation for a TP production. We could have them being used through gluconeogenesis to make glucose for storage, right. So just remember these are the, basically the two functions that are possible when it comes to Glycerol metabolism.
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Glycerol Metabolism Concept 2
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In this video, we'll take a look at the stages of Glycerol metabolism. Now, glycerol metabolism begins with the hydrolysis of our tri glycerol molecule or tag into Glycerol and three fatty acids. Now, the newly released Glycerol then travels to the liver to undergo two biochemical reactions. Now, reaction one is irreversible and it's gonna consume one A TP for energy. Now, in this reaction, one, if we take a look here, we have our glycerol and by using a TP as a source of inorganic phosphate, we create Glycerol three phosphate. Now, for reaction two, it's gonna result in the transformation of Glycerol three phosphate into DH A P which is dihydroxy acetone phosphate. In this process, we use N ad positive, it becomes reduced into N A DH, it being reduced would mean that our Glycerol three phosphate is oxidized in order to form our DH A P. This gives us an overall view of Glycerol metabolism. So just keep in mind that it's composed of these two reactions or we're gonna go from Glycerol to DH A P.
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Glycerol Metabolism Example 1
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Now here in this example question, it says which of the following statements about glycerol metabolism is true. A it involves an oxidative phosphorylation step. Now, remember glycerol metabolism is happening within the cy assault of food metabolism. This represents stage two oxidative phosphorylation doesn't happen until step four. So this has nothing to do with Glycerol metabolism. If we're talking about the two steps involved, the first step is energy producing in nature. Remember, the first step is irreversible and it consumes one A TP of energy because of this. It's not energy producing. It's energy consuming a source of Glycerol is from the tag molecule and must first undergo hydrolysis. This statement is true. Remember, we're gonna start out with our tag molecule and undergoes hydrolysis to form Glycerol and three fatty acids. It's this newly created Glycerol molecule that can then undergo metabolism. So, C is a true statement. Uh Hydrolase enzyme can be used in the first step to convert Glycerol to Glycerol three phosphate. All right. So here hydrolase, we're trying to hydrolyze this enzyme. Remember what's happening. We're going from Glycerol to Glycerol rep phosphate. And if you've watched my videos earlier videos on enzymes, we know that if we're going to add an inorganic phosphate to our starting molecule that would involve a kinase enzyme, not a hydrolase enzyme. So this statement is incorrect. So here, the only statement that's true would have to be option C.
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Glycerol Metabolism Concept 3
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Now, our tag molecule has undergone hydrolysis to create our Glycerol molecule. The glycerol molecule then enters stage one or reaction one of glycerol metabolism. We're gonna say here that reaction one is a phosphorylation reaction. Here, the enzyme Glycerol kinase catalyzes the phosphorylation of glycerol. So here we have Glycerol kinase as our enzyme being used. Here's our Glycerol molecule. We have to use a TP as a source of not only energy but inorganic phosphate. So a TP will relinquish or give up one of its phosphate groups changing it into AD P. And then we're gonna say here that, that inorganic phosphate group goes to carbon. Number three of the Glycerol molecule transforming it into Glycerol three phosphate. Here we'd write it as po 32 minus. So this is our newly created Glycerol three phosphate molecule. We're using a kinase. Remember that helps in the transferring of a inorganic phosphate group from one molecule to another. This represents phosphorylation reaction. One of Glycerol metabolism
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Glycerol Metabolism Concept 4
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Now reaction, two of glycerol metabolism represents an oxidation reaction. Remember when we've talked about oxidation reactions. In the past, the class of enzyme we utilized was dehydrogenase. So here we're going to say the dehydrogenase enzyme oxidizes glycerol three phosphate to dihydroxy acetone phosphate, otherwise known as DH A P. Now, here we utilized one N ad positive. It's going to be reduced to one N A. DH N A DH represents an energetic molecule. If we take a look here, we have Glycerol three phosphate as our substrate are beginning material for reaction to N ad positive gets reduced. So that Glycerol three phosphate can be oxidized. The enzyme we utilize is Glycerol three phosphate dehydrogenase. Remember the name of the enzyme is just the substrate name followed by the class of enzyme. Again, oxidation reactions, we've utilized dehydrogenase as a class of enzymes in previous sections. Now, here, Dihydroxyacetone, we still have our inorganic phosphate here. And what we have occur is we have a secondary alcohol here in the middle, it gets oxidized to a ketone giving us DH A P. Now DH A P should be familiar because we've covered this molecule as well. Recall that DH A P can then directly enter reaction five of glycolysis or reaction eight of gluconeogenesis. Ok. So this would represent the second reaction of glycerol metabolism.
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example
Glycerol Metabolism Example 2
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If we take a look here at this example, question, it says which of the following statements is true in regard to Glycerol metabolism. Here. The first step involves the use of a kinase that phosphor relates a secondary alcohol group. Remember we're changing Glycerol to Glycerol three phosphate. That alcohol represents not a secondary alcohol but a primary alcohol. So this would not be true. ND positive represents a high energy molecule produced during step two. No, it's not N ad positive. That represents the high energy molecule produced. Instead it's N A DH an isomerase enzyme could be used for the conversion of Glycerol three phosphate to DH A P. Now remember an isomerase would just create another isomer for Glycerol from Glycerol three phosphate. That would mean that we have the same number of elements in both compounds. But we're not using an isomerase, we're doing an oxidation. So we're using a dehydrogenase. We're actually losing elements. DH A P and Glycerol three phosphate don't have the same molecular formula. Therefore, they're not isomers of each other. So an isomerase wouldn't have been used. So this leaves D as our answer here. The A TP molecule serves as a phosphate source to phosphor, a primary alcohol group. That's correct. Remember, we're going from Glycerol to Glycerol three phosphate. We are adding an inorganic phosphate to a primary carbon. It was a primary alcohol when we've phosphorated it. So here, the only answer that's correct would have to be option D.
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Problem
Problem
Which of the following outlines the overall pathway of glycerol metabolism?
The glycerol derived from lipolysis of a triglyceride molecule is converted into glycerol-3-phosphate followed by dihydroxyacetone phosphate. Which step does this dihydroxyacetone phosphate enter in terms of glycolysis?
A
Step 1
B
Step 3
C
Step 5
D
Step 10
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