Amino acids: maple syrup urine disease: 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 · Amino acids: maple syrup urine disease

Sample item

Deficiency of branched-chain alpha-ketoacid dehydrogenase causes accumulation of which amino acids?

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

The answer and the reasoning

A. Leucine, isoleucine, and valine

Maple syrup urine disease impairs metabolism of the branched-chain amino acids leucine, isoleucine, and valine. Toxic accumulation causes poor feeding, neurologic dysfunction, and characteristic odor.

Option by option

  • A. Leucine, isoleucine, and valine (correct)

    Correct. These three are the branched-chain amino acids.

  • B. Glycine, serine, and alanine

    These are small nonessential amino acids.

  • C. Methionine, cysteine, and taurine

    These sulfur-containing compounds use different pathways.

  • D. Phenylalanine, tyrosine, and tryptophan

    This group is aromatic, not branched-chain.

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 A, Leucine, isoleucine, and valine. Maple syrup urine disease impairs metabolism of the branched-chain amino acids leucine, isoleucine, and valine.

Why is "Glycine, serine, and alanine" not the answer?

These are small nonessential amino acids.

Why is "Methionine, cysteine, and taurine" not the answer?

These sulfur-containing compounds use different pathways.

Why is "Phenylalanine, tyrosine, and tryptophan" not the answer?

This group is aromatic, not branched-chain.

What concept does this question test?

It tests Amino acids: maple syrup urine disease in Biochemistry. Toxic accumulation causes poor feeding, neurologic dysfunction, and characteristic odor.

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 Amino acids: maple syrup urine disease?

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.