Translation: aminoacyl-tRNA synthetase: 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 · Translation: aminoacyl-tRNA synthetase

Sample item

Activating each amino acid for protein synthesis costs the equivalent of two high-energy phosphate bonds, because ATP is cleaved to AMP and pyrophosphate, which is then hydrolysed. Which enzyme catalyses this activation?

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

The answer and the reasoning

B. Aminoacyl-tRNA synthetase

Formation of the aminoacyl-adenylate releases pyrophosphate, and its hydrolysis drives the reaction forward, using two high-energy bonds per amino acid. Further GTP is used during elongation, in delivery and translocation. Peptide bond formation itself needs no extra energy because the bond comes from the charged transfer RNA.

Option by option

  • A. Translocase

    Translocase uses GTP to advance the ribosome and does not activate amino acids.

  • B. Aminoacyl-tRNA synthetase (correct)

    Correct. Charging splits ATP to AMP and pyrophosphate, costing two high-energy bonds.

  • C. Peptidyl transferase

    Peptidyl transferase forms the peptide bond using energy already stored in the charged transfer RNA.

  • D. Elongation factor Tu

    Elongation factor Tu uses GTP, not ATP cleavage to AMP, to deliver the transfer RNA.

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 B, Aminoacyl-tRNA synthetase. Formation of the aminoacyl-adenylate releases pyrophosphate, and its hydrolysis drives the reaction forward, using two high-energy bonds per amino acid.

Why is "Translocase" not the answer?

Translocase uses GTP to advance the ribosome and does not activate amino acids.

Why is "Peptidyl transferase" not the answer?

Peptidyl transferase forms the peptide bond using energy already stored in the charged transfer RNA.

Why is "Elongation factor Tu" not the answer?

Elongation factor Tu uses GTP, not ATP cleavage to AMP, to deliver the transfer RNA.

What concept does this question test?

It tests Translation: aminoacyl-tRNA synthetase in Biochemistry. Further GTP is used during elongation, in delivery and translocation. Peptide bond formation itself needs no extra energy because the bond comes from the charged transfer RNA.

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 Translation: aminoacyl-tRNA synthetase?

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.