Final answer:
Penicillin inhibits bacterial cell wall synthesis by targeting the enzyme transpeptidase, disrupting cell wall integrity and causing bacterial cells to burst. This mode of action is selectively toxic to bacteria, as human cells lack cell walls. Alternative antibiotics are available for those allergic to penicillin.
Step-by-step explanation:
Penicillin functions as an antimicrobial agent by inhibiting bacterial cell wall synthesis. It specifically targets the enzyme-transpeptidase that catalyzes the last step of bacterial cell-wall biosynthesis. Through this inhibition, penicillin prevents the formation of peptide crosslinks in the peptidoglycan layer, which is critical for maintaining the cell wall's integrity. As a result, the defective walls cause bacterial cells to burst due to osmotic pressure. This process exemplifies selective toxicity because human cells, which have cell membranes and not cell walls, are left unharmed by penicillin.
Cell wall synthesis inhibitors, such as penicillin and cephalosporins, are crucial in the fight against bacterial infections. They are particularly effective against Gram-positive bacteria. Among the penicillins, penicillin G is used intravenously and penicillin V orally, while semisynthetic penicillins have been developed to target a broader spectrum of bacteria.
In contrast to penicillin, other antibiotics like metronidazole and rifampin function by inhibiting nucleic acid synthesis, affecting DNA replication and RNA polymerase activity, respectively. Moreover, antibiotics such as tetracycline and chloramphenicol block protein synthesis in bacteria. It's important to note that a small percentage of the population is allergic to penicillin, potentially leading to severe reactions. Alternative antibiotics are available that have different mechanisms of action and can be used when penicillin is contraindicated.