If aminoacyl-tRNA synthetase fails to function properly, what part of protein synthesis will cease?

Question

BlackTom AI · Accepted Answer

Aminoacyl-tRNA synthetases catalyze the attachment (charging) of specific amino acids to their corresponding tRNAs, so failure of these enzymes prevents formation of aminoacyl-tRNAs. Each synthetase recognizes one amino acid and the appropriate set of tRNA isoacceptors, using ATP to drive the reaction: amino acid + tRNA + ATP → aminoacyl‑tRNA + AMP + PPi. This charging is essential before a tRNA can deliver its amino acid to the ribosome during translation elongation.

Step-by-step reasoning:
1. Protein synthesis requires charged tRNAs: during elongation, the ribosome accepts an aminoacyl‑tRNA whose anticodon base-pairs with the mRNA codon; the ribosome then catalyzes peptide bond formation using the amino acid attached to that tRNA.
2. Aminoacyl‑tRNA synthetases perform the prerequisite chemical step of linking the correct amino acid to the correct tRNA (the “charging” step). If the synthetase fails, that chemical reaction cannot occur, so the pool of charged tRNAs for the corresponding amino acids is depleted.
3. Without charged tRNAs for particular codons, the ribosome cannot add those specific amino acids at the corresponding positions in a growing polypeptide; translation will stall at codons requiring those aminoacyl‑tRNAs.

Why the correct answer is correct: the direct molecular function of aminoacyl‑tRNA synthetases is to attach specific amino acids to specific tRNAs. Their failure therefore leads exactly to the stated outcome: specific amino acids will not be attached to specific tRNAs.

Why the other options are incorrect:
- “mRNA will not be transcribed”: transcription is performed by RNA polymerases in the nucleus (or by phage polymerases) and is independent of tRNA synthetase activity.
- “ribosomes will not form”: ribosome assembly involves rRNA and ribosomal proteins, not tRNA charging.
- “tRNA will not match its anticodon with the codon on mRNA”: base-pairing between tRNA anticodon and mRNA codon is a separate molecular recognition process; synthetases are not responsible for anticodon-codon pairing (though uncharged tRNAs cannot donate an amino acid).

Conclusion: therefore, the correct choice is “specific amino acids will not be attached to specific tRNAs,” which matches the provided answer.

If aminoacyl-tRNA synthetase fails to function properly, what part of protein synthesis will cease?单项选择题

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