Question

The following is not an inhibitor of protein synthesis

• A. Streptomycin
• B. Penicillin
• C. Tetracyclin
• D. Erythromycin

Hint:

• Antibiotics targeting bacterial protein synthesis often act on the 30S or 50S ribosomal subunits. Examples:
  • 30S inhibitors: Aminoglycosides (e.g., Streptomycin, Gentamicin), Tetracyclines.
  • 50S inhibitors: Macrolides (e.g., Erythromycin, Azithromycin), Chloramphenicol, Clindamycin, Linezolid.
• \(\beta\)-lactam antibiotics (e.g., Penicillins, Cephalosporins) inhibit bacterial cell wall synthesis.

Answer 1

The Correct Option is B

Many antibiotics work by inhibiting bacterial protein synthesis, typically by targeting the bacterial ribosome.

• (a) Streptomycin: An aminoglycoside antibiotic that binds to the 30S subunit of the bacterial ribosome, causing misreading of mRNA and inhibiting protein synthesis. It IS an inhibitor.
• (b) Penicillin: A \(\beta\)-lactam antibiotic. Penicillins work by inhibiting the synthesis of peptidoglycan, a crucial component of the bacterial cell wall. They do NOT directly inhibit protein synthesis.
• (c) Tetracyclin (Tetracycline): Binds to the 30S ribosomal subunit and blocks the attachment of aminoacyl-tRNA to the A-site of the ribosome, thus inhibiting protein synthesis. It IS an inhibitor.
• (d) Erythromycin: A macrolide antibiotic that binds to the 50S subunit of the bacterial ribosome and inhibits translocation (movement of the ribosome along mRNA) or peptide chain elongation. It IS an inhibitor.

Therefore, Penicillin is not an inhibitor of protein synthesis; it targets cell wall synthesis. \[ \boxed{\text{Penicillin}} \]