B/B Section Bank Question 81

[itsalwayssunny96]

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I answered the question correctly but I am still confused. How is alpha-ketoglutarate a precursor to gluconeogenesis? I know it's involved in the TCA cycle but how does that make it a precursor to making glucose?

Also, I knew oxaloacetate was correct because I remembered that when the oxidation of FA's yields an odd number of carbons, this intermediate is formed and eventually makes succinyl CoA which can be formed into oxaloacetate (which serves as a precursor for gluconeogenesis). And I knew lactate could become glucose via the Cori cycle.

 

[aldol16]

TCA cycle intermediates like alpha-ketoglutarate can be converted into oxaloacetate.

 

[itsalwayssunny96]

TCA cycle intermediates like alpha-ketoglutarate can be converted into oxaloacetate.

So then anything from the TCA cycle is technically a glucogenic precursor ? Can citrate be one? Or does it have to be past the isocitrate dehydrogenase rate-limiting step?

 

[aldol16]

So then anything from the TCA cycle is technically a glucogenic precursor ? Can citrate be one? Or does it have to be past the isocitrate dehydrogenase rate-limiting step?

All the TCA cycle intermediates that can be used to form oxaloacetate. Acetyl-CoA doesn't work because that step is irreversible.

 

[itsalwayssunny96]

All the TCA cycle intermediates that can be used to form oxaloacetate. Acetyl-CoA doesn't work because that step is irreversible.

Thanks man!

 

[yeasureyoubetcha]

After hepatic glycogen is depleted, GNG will be happening. The reason you can't convert acetyl coa to glucose through GNG is that as you convert OAA to malate for transport through the malate shuttle, you remove substrate from the mitochondria necessary for the citrate synthase step, and cease to be able to incorporate acetyl coa into the cycle since OAA isn't around anymore. High acetyl coa will keep that cell alive, but won't sustain blood glucose. After OAA is removed TCA will actually slow due do high NADH and acetyl coa will be shunted to ketogenesis


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[Squish miss]

but this seems like acetyl co a can be used