Which two antibiotics are classic examples that inhibit the 30S ribosomal subunit?

Which two antibiotics are classic examples that inhibit the 30S ribosomal subunit?

• A. Chloramphenicol and Erythromycin
• B. Aminoglycosides and Tetracycline
• C. Penicillin and Cephalosporin
• D. Sulfamethoxazole and Trimethoprim

Answer: (B)

The key idea here is that certain antibiotics block protein synthesis by targeting the 30S ribosomal subunit. The classic examples are aminoglycosides and tetracyclines. Aminoglycosides bind to the 16S rRNA in the 30S subunit, causing misreading of the genetic code and preventing the formation of the initiation complex, which usually leads to bacterial death. Tetracyclines attach to the 30S A site and prevent the attachment of aminoacyl-tRNA, stopping elongation of the growing peptide chain. That combination of mechanisms makes them well-known inhibitors of the 30S ribosomal subunit. In contrast, the other options act on different targets: chloramphenicol and erythromycin inhibit the 50S subunit, blocking peptide bond formation or translocation; penicillin and cephalosporins disrupt cell wall synthesis; sulfamethoxazole and trimethoprim interrupt folate synthesis.

The key idea here is that certain antibiotics block protein synthesis by targeting the 30S ribosomal subunit. The classic examples are aminoglycosides and tetracyclines. Aminoglycosides bind to the 16S rRNA in the 30S subunit, causing misreading of the genetic code and preventing the formation of the initiation complex, which usually leads to bacterial death. Tetracyclines attach to the 30S A site and prevent the attachment of aminoacyl-tRNA, stopping elongation of the growing peptide chain. That combination of mechanisms makes them well-known inhibitors of the 30S ribosomal subunit.

In contrast, the other options act on different targets: chloramphenicol and erythromycin inhibit the 50S subunit, blocking peptide bond formation or translocation; penicillin and cephalosporins disrupt cell wall synthesis; sulfamethoxazole and trimethoprim interrupt folate synthesis.