Collagen synthesis: vitamin C: 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.

Try it

Biochemistry · Collagen synthesis: vitamin C

Sample item

A water-soluble vitamin is a cofactor for the copper enzyme that converts dopamine to norepinephrine in chromaffin granules. It also keeps the iron of collagen-modifying hydroxylases in the reduced state. Which vitamin is this?

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

The answer and the reasoning

A. Vitamin C

Ascorbate donates electrons to dopamine beta-hydroxylase and to prolyl and lysyl hydroxylases, which is why it matters for both catecholamine synthesis and collagen stability. It also enhances non-haem iron absorption. Its absence causes scurvy.

Option by option

  • A. Vitamin C (correct)

    Correct. Ascorbate is the electron donor for both dopamine beta-hydroxylase and the collagen hydroxylases.

  • B. Vitamin B6

    Vitamin B6 is the cofactor for decarboxylases and transaminases, including DOPA decarboxylase, not dopamine hydroxylation.

  • C. Niacin

    Niacin forms NAD and NADP for dehydrogenases and does not support these hydroxylases.

  • D. Folic acid

    Folic acid carries one-carbon units and does not act as a hydroxylase cofactor.

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.

More Biochemistry questions

Questions about this Biochemistry question

What is the answer to this Biochemistry question?

The best answer is A, Vitamin C. Ascorbate donates electrons to dopamine beta-hydroxylase and to prolyl and lysyl hydroxylases, which is why it matters for both catecholamine synthesis and collagen stability.

Why is "Vitamin B6" not the answer?

Vitamin B6 is the cofactor for decarboxylases and transaminases, including DOPA decarboxylase, not dopamine hydroxylation.

Why is "Niacin" not the answer?

Niacin forms NAD and NADP for dehydrogenases and does not support these hydroxylases.

Why is "Folic acid" not the answer?

Folic acid carries one-carbon units and does not act as a hydroxylase cofactor.

What concept does this question test?

It tests Collagen synthesis: vitamin C in Biochemistry. It also enhances non-haem iron absorption. Its absence causes scurvy.

How hard is this question?

We tag it as a multi-step question: it asks you to combine more than one idea. 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 Collagen synthesis: vitamin C?

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.