Lipid metabolism: 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

Sample item

Why can the liver produce ketone bodies but not use them as a major fuel source?

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

The answer and the reasoning

C. It lacks thiophorase

Hepatocytes lack thiophorase, the enzyme needed to activate ketone bodies for oxidation, so the liver exports acetoacetate and beta-hydroxybutyrate for use by extrahepatic tissues.

Option by option

  • A. It lacks glycogen phosphorylase

    Glycogen phosphorylase is present in liver for glycogen breakdown.

  • B. It lacks citrate synthase

    Citrate synthase is present and participates in the tricarboxylic acid cycle.

  • C. It lacks thiophorase (correct)

    Correct: absent thiophorase prevents hepatic ketone-body utilization.

  • D. It lacks lactate dehydrogenase

    Lactate dehydrogenase is present for lactate-pyruvate interconversion.

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 C, It lacks thiophorase. Hepatocytes lack thiophorase, the enzyme needed to activate ketone bodies for oxidation, so the liver exports acetoacetate and beta-hydroxybutyrate for use by extrahepatic tissues.

Why is "It lacks glycogen phosphorylase" not the answer?

Glycogen phosphorylase is present in liver for glycogen breakdown.

Why is "It lacks citrate synthase" not the answer?

Citrate synthase is present and participates in the tricarboxylic acid cycle.

Why is "It lacks lactate dehydrogenase" not the answer?

Lactate dehydrogenase is present for lactate-pyruvate interconversion.

What concept does this question test?

It tests Lipid metabolism in Biochemistry. The correct option holds because: Correct: absent thiophorase prevents hepatic ketone-body utilization.

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?

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.