Question:
The antibiotic that inhibits protein synthesis by premature chain termination and which structurally resembles aminoacyl tRNA is
The antibiotic that inhibits protein synthesis by premature chain termination and which structurally resembles aminoacyl tRNA is
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Puromycin mimics the aminoacyl end of tRNA and causes premature release of the growing peptide chain.
Updated On: Jul 8, 2026
- Tetracycline
- Chloramphenicol
- Puromycin
- Erythromycin
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The Correct Option is C
Solution and Explanation
Step 1: Understanding the Question:
The question wants an antibiotic that looks structurally like aminoacyl tRNA (the tRNA molecule carrying an amino acid) and that stops protein synthesis by ending the growing chain early instead of by some other mechanism.
Step 2: Key Concept:
Puromycin is famous for mimicking the 3' end of an aminoacyl tRNA. Because ribosomes cannot tell it apart from a real aminoacyl tRNA, it enters the ribosomal A site and gets added to the growing polypeptide chain, just like a normal amino acid would be.
Step 3: Detailed Explanation:
Once puromycin is added to the chain, the chain cannot continue growing, because puromycin lacks the normal chemical group needed for the next peptide bond to form. The protein falls off the ribosome early, in a truncated, non-functional form. This is called premature chain termination, and it happens in both bacteria and human cells, which is why puromycin is toxic to both and used mainly as a laboratory tool rather than a clinical antibiotic.
Tetracycline works by a different method: it blocks the A site of the bacterial ribosome so that no new aminoacyl tRNA can bind at all, rather than entering the site itself. Chloramphenicol blocks the peptidyl transferase enzyme that forms peptide bonds, stopping chain growth without resembling tRNA. Erythromycin binds the 50S ribosomal subunit and blocks translocation, the movement of the ribosome along mRNA, again without mimicking tRNA structurally. None of these three enter the ribosome disguised as an amino acid carrier the way puromycin does.
Step 4: Final Answer:
Puromycin is the antibiotic that structurally resembles aminoacyl tRNA and causes premature chain termination, option (3).
The question wants an antibiotic that looks structurally like aminoacyl tRNA (the tRNA molecule carrying an amino acid) and that stops protein synthesis by ending the growing chain early instead of by some other mechanism.
Step 2: Key Concept:
Puromycin is famous for mimicking the 3' end of an aminoacyl tRNA. Because ribosomes cannot tell it apart from a real aminoacyl tRNA, it enters the ribosomal A site and gets added to the growing polypeptide chain, just like a normal amino acid would be.
Step 3: Detailed Explanation:
Once puromycin is added to the chain, the chain cannot continue growing, because puromycin lacks the normal chemical group needed for the next peptide bond to form. The protein falls off the ribosome early, in a truncated, non-functional form. This is called premature chain termination, and it happens in both bacteria and human cells, which is why puromycin is toxic to both and used mainly as a laboratory tool rather than a clinical antibiotic.
Tetracycline works by a different method: it blocks the A site of the bacterial ribosome so that no new aminoacyl tRNA can bind at all, rather than entering the site itself. Chloramphenicol blocks the peptidyl transferase enzyme that forms peptide bonds, stopping chain growth without resembling tRNA. Erythromycin binds the 50S ribosomal subunit and blocks translocation, the movement of the ribosome along mRNA, again without mimicking tRNA structurally. None of these three enter the ribosome disguised as an amino acid carrier the way puromycin does.
Step 4: Final Answer:
Puromycin is the antibiotic that structurally resembles aminoacyl tRNA and causes premature chain termination, option (3).
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