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Old 04-28-2010
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Question Exclusive Mitochondrial Pathway?

Which of the following metabolic processes occurs exclusively in the mitochondria?

A. Cholesterol synthesis
B. Fatty acid synthesis
C. Gluconeogenesis
D. Glycolysis
E. Hexose monophosphate shunt
F. Ketone body synthesis
G. Urea cycle
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Old 04-28-2010
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F- ketone body synthesis
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i think it is E
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Old 04-28-2010
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Correct Answer Answer is F

This is a common USMLE question. Here's some help

Exclusively in the Mitochondria: Mnemonic BEAT
  • Fatty acid oxidation (Beta-oxidation).
  • Oxidative phosphorylation and Electron transport chain.
  • Ketone body synthesis. Acetyl Co A synthesis.
  • Krebs cycle AKA TCA cycle.
Exclusively in the Cytoplasm:
  • Glycolysis.
  • Gluconeogenesis (basically the reverse of glycolysis though you need the malate shuttle to bring oxaloacetate from the mitochondria.
  • Hexose Mono Phosphate (HMP) shunt.
  • Cholestrol synthesis (as it needs the above two to supply Acetyl CoA and NADPH respectively).
  • Protein synthesis (RER).
  • Steroid synthesis (SER).
Both mitochondria and cytoplasm:
  • Heme synthesis.
  • Urea cycle (Where you have ornithine and citrulline jumping between the two sides).
  • Gluconeogenesis (this is listed here in FA, but see note above).
  • Fatty acid synthesis (this is not listed here in FA but citrate shuttle needed between the mitochondria and the cytoplasm).
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Old 04-29-2010
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Quote:
Originally Posted by lee-usmle View Post
This is a common USMLE question. Here's some help

Exclusively in the Mitochondria: Mnemonic BEAT
  • Fatty acid oxidation (Beta-oxidation).
  • Oxidative phosphorylation and Electron transport chain.
  • Ketone body synthesis. Acetyl Co A synthesis.
  • Krebs cycle AKA TCA cycle.
Exclusively in the Cytoplasm:
  • Glycolysis.
  • Gluconeogenesis (basically the reverse of glycolysis though you need the malate shuttle to bring oxaloacetate from the mitochondria.
  • Hexose Mono Phosphate (HMP) shunt.
  • Cholestrol synthesis (as it needs the above two to supply Acetyl CoA and NADPH respectively).
  • Protein synthesis (RER).
  • Steroid synthesis (SER).
Both mitochondria and cytoplasm:
  • Heme synthesis.
  • Urea cycle (Where you have ornithine and citrulline jumping between the two sides).
  • Gluconeogenesis (this is listed here in FA, but see note above).
  • Fatty acid synthesis (this is not listed here in FA but citrate shuttle needed between the mitochondria and the cytoplasm).
i don t understand why you put gluconeogenesis in exclusively mitochondria.Doesn it occur in both
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Old 04-29-2010
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Wink Yes, you are right

Quote:
Originally Posted by sam01 View Post
i don t understand why you put gluconeogenesis in exclusively mitochondria.Doesn it occur in both
I did not put it in the mitochondria, I put it in the cytoplasm.
I mentioned why there,
Gluconeogenesis is simply the reverse of glycolysis and most of the reactions happen in the cytoplasm.
However, indeed you have Pyruvate carboxylase in the mitochondria which is needed to convert Pyruvate to OAA which will then enter the chain via the mallate shuttle back to the cytoplasm.

You are right we can consider gluconeogenesis as happening in both
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Old 04-29-2010
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Quote:
Originally Posted by lee-usmle View Post
I did not put it in the mitochondria, I put it in the cytoplasm.
I mentioned why there,
Gluconeogenesis is simply the reverse of glycolysis and most of the reactions happen in the cytoplasm.
However, indeed you have Pyruvate carboxylase in the mitochondria which is needed to convert Pyruvate to OAA which will then enter the chain via the mallate shuttle back to the cytoplasm.

You are right we can consider gluconeogenesis as happening in both
ok thanks ,i was just a little confused
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