Amino-acid metabolism: 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

Sample item

What is the main physiological purpose of the hepatic urea cycle?

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

The answer and the reasoning

A. Convert toxic ammonia into urea

The urea cycle detoxifies ammonia generated during amino-acid catabolism by converting it into water-soluble urea, which is transported to the kidneys and excreted in urine.

Option by option

  • A. Convert toxic ammonia into urea (correct)

    Correct: the urea cycle safely disposes of nitrogen as urea.

  • B. Generate oxygen from water

    Humans do not generate oxygen from water metabolically.

  • C. Synthesize essential fatty acids

    Humans do not synthesize essential fatty acids through the urea cycle.

  • D. Produce glucose from glycogen

    Glycogen breakdown is glycogenolysis, not a urea-cycle function.

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, Convert toxic ammonia into urea. The urea cycle detoxifies ammonia generated during amino-acid catabolism by converting it into water-soluble urea, which is transported to the kidneys and excreted in urine.

Why is "Generate oxygen from water" not the answer?

Humans do not generate oxygen from water metabolically.

Why is "Synthesize essential fatty acids" not the answer?

Humans do not synthesize essential fatty acids through the urea cycle.

Why is "Produce glucose from glycogen" not the answer?

Glycogen breakdown is glycogenolysis, not a urea-cycle function.

What concept does this question test?

It tests Amino-acid metabolism in Biochemistry. The correct option holds because: Correct: the urea cycle safely disposes of nitrogen as urea.

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?

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.