Penicillin Targets Bacterial Cell Wall Synthesis

Steps:

• Recall that penicillin is an antibiotic specific to bacteria with peptidoglycan cell walls.
• Identify its mechanism: binds to enzymes involved in cross-linking peptidoglycan, weakening the wall.
• Evaluate options: A and B relate to nucleic acid/protein processes, not cell walls; D misplaces the target to protein synthesis.
• Confirm C matches the inhibition of cell wall enzyme activity.

Why C is correct:

• Penicillin acts as a competitive inhibitor by binding to the active site of transpeptidase (penicillin-binding proteins), blocking peptidoglycan cross-linking essential for bacterial cell wall integrity, per the definition of competitive inhibition in enzyme kinetics.

Why the others are wrong:

• A: DNA replication inhibition (e.g., by quinolones) prevents tRNA-ribosome binding? Incorrect; that's unrelated to penicillin.
• B: Translation inhibition by blocking tRNA binding occurs with antibiotics like tetracyclines, not penicillin.
• D: Protein synthesis enzymes are targeted by drugs like streptomycin, not cell wall ones by penicillin.

Final answer: C