Achiever Bio 3 : Question 21

[TheWiredNerv]

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One statement that the question makes is that Glycerol will not enter the Kreb's cycle as Acetyl CoA. I thought glycerol could be oxidized to pyruvate which can then be oxidized into acetyl CoA and enter the Krebs Cycle. I had a difficult time with this question as I thought every answer was right. Is this a pick the least right answer since the conversion of glycerol to acetyl CoA takes some steps?

 

[Shunwei]

One statement that the question makes is that Glycerol will not enter the Kreb's cycle as Acetyl CoA. I thought glycerol could be oxidized to pyruvate which can then be oxidized into acetyl CoA and enter the Krebs Cycle. I had a difficult time with this question as I thought every answer was right. Is this a pick the least right answer since the conversion of glycerol to acetyl CoA takes some steps?

Glycerol is a 3C compound, and therefore it can enter the glycolytic cycle after being converted to G3AP or DHAP. After processing through this cycle, it can then enter Krebs cycle if necessary. All of the Krebs cycle intermediates (succinate, malate, oxaloacetate) are 4C. This is why Fat is such a good source of energy, because beta-oxidation can lop off 2C pieces that can then be covalently bonded to Co-A and directly enter Krebs.

 

[TheWiredNerv]

Yes but glycerol will still eventually enter the Kreb's cycle as pyruvate, so I don't know why achiever says this is false. Perhaps they implied directness.