TCA cycle: anaplerosis: 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 · TCA cycle: anaplerosis

Sample item

Which reaction replenishes oxaloacetate for the TCA cycle during gluconeogenesis?

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

The answer and the reasoning

D. Pyruvate carboxylase reaction

Pyruvate carboxylase converts pyruvate to oxaloacetate in mitochondria and is an anaplerotic reaction. It requires biotin and is activated by acetyl-CoA.

Option by option

  • A. Hexokinase reaction

    Hexokinase phosphorylates glucose.

  • B. Pyruvate dehydrogenase reaction

    Pyruvate dehydrogenase produces acetyl-CoA but does not replenish oxaloacetate.

  • C. Lactate dehydrogenase reaction

    Lactate dehydrogenase interconverts lactate and pyruvate.

  • D. Pyruvate carboxylase reaction (correct)

    Correct. This reaction replenishes oxaloacetate.

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, Pyruvate carboxylase reaction. Pyruvate carboxylase converts pyruvate to oxaloacetate in mitochondria and is an anaplerotic reaction.

Why is "Hexokinase reaction" not the answer?

Hexokinase phosphorylates glucose.

Why is "Pyruvate dehydrogenase reaction" not the answer?

Pyruvate dehydrogenase produces acetyl-CoA but does not replenish oxaloacetate.

Why is "Lactate dehydrogenase reaction" not the answer?

Lactate dehydrogenase interconverts lactate and pyruvate.

What concept does this question test?

It tests TCA cycle: anaplerosis in Biochemistry. It requires biotin and is activated by acetyl-CoA.

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 TCA cycle: anaplerosis?

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.