How does penicillin weaken a bacterial cell wall?

Penicillin weakens a bacterial cell wall through a dual-action process that targets the microorganism during its replication phase. Specifically, the antibiotic functions by inhibiting the bacterial enzymes responsible for synthesizing the cell wall. Simultaneously, it activates other enzymes that actively break down the existing protective structure of the cell wall.1

This process disrupts the final stages of cell wall assembly, particularly the cross-linking of wall material strands. Because human cells lack cell walls, they are not harmed by this mechanism. Consequently, penicillin is only effective against bacteria that are actively replicating and producing new cell walls. As the structural integrity of the wall is compromised, the bacterium loses its shape and eventually dies.21