What is the name of the bacterial cell wall component targeted by penicillin?

The bacterial cell wall component targeted by penicillin is peptidoglycan. This tough, mesh-like polymer surrounds many bacterial cells and prevents them from bursting when water moves into them.

Penicillin does not simply dissolve peptidoglycan. Its beta-lactam ring binds to penicillin-binding proteins, especially transpeptidase enzymes that cross-link peptidoglycan strands during the final stage of cell-wall construction. With cross-linking blocked, wall synthesis cannot keep pace with normal growth and breakdown. The weakened cell eventually ruptures through osmotic pressure, particularly while it is growing or dividing.

This mechanism explains why penicillin is selective: human cells have no peptidoglycan cell wall. Gram-positive bacteria are often especially susceptible because their thick peptidoglycan layer is exposed. Gram-negative bacteria have a thinner layer protected by an outer membrane, which can reduce drug entry. Resistance commonly arises when bacteria produce beta-lactamases that destroy penicillin or alter their penicillin-binding proteins.