Amino acid metabolism: glutamate dehydrogenase: 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 · Amino acid metabolism: glutamate dehydrogenase

Sample item

Which mitochondrial enzyme reversibly converts glutamate to alpha-ketoglutarate and ammonia using NAD+ or NADP+, and is allosterically activated by ADP?

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

The answer and the reasoning

A. Glutamate dehydrogenase

Glutamate dehydrogenase links amino acid and carbohydrate metabolism by oxidative deamination of glutamate, releasing free ammonia for the urea cycle. It is activated by ADP and GDP, signalling low energy, and inhibited by ATP and GTP. Transaminases first funnel amino groups to glutamate.

Option by option

  • A. Glutamate dehydrogenase (correct)

    Correct. This enzyme performs the oxidative deamination of glutamate and is regulated by energy state.

  • B. Glutamine synthetase

    Glutamine synthetase adds ammonia to glutamate using ATP and does not use NAD+.

  • C. Glutaminase

    Glutaminase hydrolyses glutamine to glutamate and does not use NAD+ or NADP+.

  • D. Alanine aminotransferase

    Alanine aminotransferase transfers an amino group and does not release free ammonia.

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, Glutamate dehydrogenase. Glutamate dehydrogenase links amino acid and carbohydrate metabolism by oxidative deamination of glutamate, releasing free ammonia for the urea cycle.

Why is "Glutamine synthetase" not the answer?

Glutamine synthetase adds ammonia to glutamate using ATP and does not use NAD+.

Why is "Glutaminase" not the answer?

Glutaminase hydrolyses glutamine to glutamate and does not use NAD+ or NADP+.

Why is "Alanine aminotransferase" not the answer?

Alanine aminotransferase transfers an amino group and does not release free ammonia.

What concept does this question test?

It tests Amino acid metabolism: glutamate dehydrogenase in Biochemistry. It is activated by ADP and GDP, signalling low energy, and inhibited by ATP and GTP. Transaminases first funnel amino groups to glutamate.

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: glutamate dehydrogenase?

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.