Enzymes: vitamin K: 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 · Enzymes: vitamin K

Sample item

Warfarin therapy impairs gamma-carboxylation of clotting factors. Which amino acid normally undergoes this modification?

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

The answer and the reasoning

C. Glutamate

Vitamin K-dependent gamma-carboxylation converts glutamate residues to gamma-carboxyglutamate, allowing factors II, VII, IX and X to bind calcium and phospholipid surfaces.

Option by option

  • A. Methionine

    Methionine is the initiator amino acid and methyl donor precursor.

  • B. Glycine

    Glycine is abundant in collagen but is not vitamin K carboxylated.

  • C. Glutamate (correct)

    Correct. Gamma-carboxyglutamate residues bind calcium.

  • D. Proline

    Proline hydroxylation depends on vitamin C.

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, Glutamate. Vitamin K-dependent gamma-carboxylation converts glutamate residues to gamma-carboxyglutamate, allowing factors II, VII, IX and X to bind calcium and phospholipid surfaces.

Why is "Methionine" not the answer?

Methionine is the initiator amino acid and methyl donor precursor.

Why is "Glycine" not the answer?

Glycine is abundant in collagen but is not vitamin K carboxylated.

Why is "Proline" not the answer?

Proline hydroxylation depends on vitamin C.

What concept does this question test?

It tests Enzymes: vitamin K in Biochemistry. The correct option holds because: Correct. Gamma-carboxyglutamate residues bind calcium.

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 Enzymes: vitamin K?

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.