Which structure is specifically targeted by β-lactam antibiotics?

β-lactam antibiotics are specifically designed to target the bacterial cell wall, making this the correct choice. The mechanism of action of β-lactam antibiotics, such as penicillin and cephalosporins, involves inhibiting the synthesis of peptidoglycan, a critical component of the bacterial cell wall. This interference leads to the weakening of the cell wall structure, ultimately resulting in cell lysis and death, particularly in actively dividing bacteria.

The cell wall is an essential feature that distinguishes bacterial cells from eukaryotic cells, which do not have a cell wall but instead possess a plasma membrane. This specificity allows β-lactam antibiotics to effectively target bacteria while leaving human cells largely unharmed. The other options—plasma membrane, DNA replication, and RNA transcription—do not directly relate to the primary action of β-lactam antibiotics, which is focused on cell wall synthesis. Therefore, understanding the targeting of β-lactam antibiotics provides insight into their therapeutic use against bacterial infections.