Lipid metabolism: carnitine shuttle: 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: carnitine shuttle

Sample item

Long-chain fatty acids require which molecule to enter the mitochondrial matrix for beta-oxidation?

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

The answer and the reasoning

C. Carnitine

The carnitine shuttle transfers long-chain fatty acyl groups across the inner mitochondrial membrane. Malonyl-CoA inhibits carnitine palmitoyltransferase I during fatty-acid synthesis.

Option by option

  • A. Cobalamin

    Cobalamin is required for methylmalonyl-CoA mutase and methionine synthase.

  • B. Tetrahydrofolate

    Tetrahydrofolate transfers one-carbon units.

  • C. Carnitine (correct)

    Correct. Carnitine carries long-chain acyl groups into mitochondria.

  • D. Biotin

    Biotin carries carbon dioxide in carboxylation reactions.

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, Carnitine. The carnitine shuttle transfers long-chain fatty acyl groups across the inner mitochondrial membrane.

Why is "Cobalamin" not the answer?

Cobalamin is required for methylmalonyl-CoA mutase and methionine synthase.

Why is "Tetrahydrofolate" not the answer?

Tetrahydrofolate transfers one-carbon units.

Why is "Biotin" not the answer?

Biotin carries carbon dioxide in carboxylation reactions.

What concept does this question test?

It tests Lipid metabolism: carnitine shuttle in Biochemistry. Malonyl-CoA inhibits carnitine palmitoyltransferase I during fatty-acid synthesis.

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: carnitine shuttle?

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.