Final answer:
Penicillin inhibits the synthesis of bacterial cell walls by interfering with the transpeptidase enzyme, preventing the cross-linking of peptidoglycan layers which leads to bacterial lysis. Belonging to ß-lactam antibiotics, its mechanism is selectively toxic to bacteria without affecting human cells. option b.
Step-by-step explanation:
The mechanism of action of penicillin is to inhibit cell wall synthesis of the pathogen. It operates by irreversibly inhibiting the enzyme transpeptidase, which catalyzes the formation of peptide bonds that are critical for maintaining the strength and rigidity of the bacterial cell wall. Without this cross-linking, the peptidoglycan layer is compromised, leading to the lysis and death of the bacteria.
Penicillins are part of a broader class known as ß-lactam antibiotics, which share a common active site in their structure known as the ß-lactam ring. This ring is crucial for the drug's antibacterial activity, allowing it to interact with penicillin-binding proteins and to block the crosslinking of peptide chains during the biosynthesis of peptidoglycan. This leads to weak cell walls that allow water to flow into the cell, causing it to burst. Human cells are unaffected by penicillin because they do not have cell walls.
Penicillins' selective toxicity towards bacteria and the development of semisynthetic penicillin derivatives, such as methicillin and others, have been vital in combating bacterial strains that produce penicillinase, an enzyme that can break down penicillin. This advancement in antibiotic therapy has significantly broadened the effectiveness of penicillin against a wider range of bacteria.