Amino acid metabolism: phenylketonuria: 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 acid metabolism: phenylketonuria

Sample item

A child with phenylketonuria requires supplementation with which amino acid because it becomes essential?

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

The answer and the reasoning

B. Tyrosine

Phenylalanine hydroxylase normally converts phenylalanine to tyrosine. In PKU, tyrosine must be supplied and phenylalanine restricted to prevent neurologic injury.

Option by option

  • A. Aspartate

    Aspartate is nonessential and produced from oxaloacetate.

  • B. Tyrosine (correct)

    Correct. Tyrosine cannot be adequately synthesised in PKU.

  • C. Alanine

    Alanine is produced readily by transamination.

  • D. Glutamate

    Glutamate is made from alpha-ketoglutarate.

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 B, Tyrosine. Phenylalanine hydroxylase normally converts phenylalanine to tyrosine.

Why is "Aspartate" not the answer?

Aspartate is nonessential and produced from oxaloacetate.

Why is "Alanine" not the answer?

Alanine is produced readily by transamination.

Why is "Glutamate" not the answer?

Glutamate is made from alpha-ketoglutarate.

What concept does this question test?

It tests Amino acid metabolism: phenylketonuria in Biochemistry. In PKU, tyrosine must be supplied and phenylalanine restricted to prevent neurologic injury.

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 acid metabolism: phenylketonuria?

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.