Lipid metabolism: ketone bodies: practice question

A Biochemistry question in the style of the NEET PG paper. Answer it first, then read why the right option is right and why each of the others is wrong.

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Biochemistry · Lipid metabolism: ketone bodies

Sample item

Why cannot hepatocytes use ketone bodies as a major fuel despite producing them during fasting?

Original practice item, not a recalled exam question. Nothing here is recorded.

The answer and the reasoning

D. They lack thiophorase

The liver lacks succinyl-CoA:acetoacetate CoA transferase (thiophorase), the enzyme required to activate ketone bodies for oxidation. It exports ketones for extrahepatic tissues.

Option by option

  • A. They lack mitochondrial HMG-CoA synthase

    HMG-CoA synthase is present in hepatic mitochondria and enables ketogenesis.

  • B. They lack beta-oxidation enzymes

    The liver performs beta-oxidation during fasting.

  • C. They cannot make acetyl-CoA

    Acetyl-CoA is produced abundantly from fatty-acid oxidation.

  • D. They lack thiophorase (correct)

    Correct. Thiophorase absence prevents hepatic ketone utilisation.

Source note: Original NextPrep sample item — pending expert review. This item is original practice material awaiting independent expert review, so confirm important facts in a standard textbook.

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Questions about this Biochemistry question

What is the answer to this Biochemistry question?

The best answer is D, They lack thiophorase. The liver lacks succinyl-CoA:acetoacetate CoA transferase (thiophorase), the enzyme required to activate ketone bodies for oxidation.

Why is "They lack mitochondrial HMG-CoA synthase" not the answer?

HMG-CoA synthase is present in hepatic mitochondria and enables ketogenesis.

Why is "They lack beta-oxidation enzymes" not the answer?

The liver performs beta-oxidation during fasting.

Why is "They cannot make acetyl-CoA" not the answer?

Acetyl-CoA is produced abundantly from fatty-acid oxidation.

What concept does this question test?

It tests Lipid metabolism: ketone bodies in Biochemistry. It exports ketones for extrahepatic tissues.

How hard is this question?

We tag it as an application question: it asks you to use a fact on a patient or a finding. The tag is our own editorial judgement, not an official difficulty rating, so read the reason for every option, not only the answer.

How should I study Lipid metabolism: ketone bodies?

Build one table of enzyme deficiency, disease, inheritance and key finding, then revise it by spaced recall. Then use the flashcards and the other Biochemistry questions on this site to test what stuck.

Is this a real NEET PG question?

No. It is an original practice item (editorial status: sample, version 1). NextPrep does not publish recalled or leaked questions, and independent faculty review of this item has not been completed yet, so confirm important facts in a standard textbook.