Final answer:
Beta-lactam antibiotics inhibit cell wall synthesis by blocking the enzyme necessary for peptidoglycan cross-linking, leading to bacterial cell death through osmotic lysis. They are selectively toxic to bacteria as human cells do not possess cell walls.
Step-by-step explanation:
Beta-lactam antibiotics work by inhibiting cell wall synthesis. They achieve this by specifically targeting the transpeptidase enzyme that catalyzes the final step in the biosynthesis of bacterial cell walls. Beta-lactam drugs, such as penicillin, cephalosporins, carbapenems, and monobactams, prevent the cross-linking of peptidoglycan chains which is crucial for cell wall integrity. As a result, bacteria are left with weakened walls that cannot prevent the cell from bursting due to osmotic pressure.
Human cells do not possess cell walls, and therefore, these antibiotics exhibit selective toxicity, meaning they specifically attack bacterial cells without harming human cells. This selective attack is what makes beta-lactams highly effective as antibacterial agents. Antibacterial compounds that inhibit cell wall synthesis, such as beta-lactams, are considered bactericidal because they directly lead to the death of the bacteria by causing osmotic lysis.