Antibiotic such as penicillin blocks _______.

Penicillin is a beta-lactam antibiotic that primarily targets the bacterial cell wall [3]. It functions by inhibiting the synthesis of peptidoglycan, a critical structural component of the bacterial cell wall [4]. Specifically, penicillin binds to penicillin-binding proteins (PBPs), such as DD-transpeptidase, which are enzymes responsible for cross-linking peptidoglycan chains [4]. By irreversibly inactivating these enzymes, penicillin prevents the formation of new peptide bonds, leading to an unstable and improperly constructed cell wall [3]. This structural failure makes the bacteria susceptible to osmotic pressure, causing water to flow into the cell and resulting in cell lysis and death [4]. Because human and animal cells lack cell walls and peptidoglycan, penicillin specifically targets bacterial cells without harming the host. Other antibiotics may target DNA or RNA synthesis, but penicillin's primary mechanism is the disruption of cell wall formation.

Sources

1. [3] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 3: Health: The Ultimate Treasure > 3.5.1 Treatment of diseases > p. 39
2. [4] https://pmc.ncbi.nlm.nih.gov/articles/PMC2896384/
3. [1] https://www.ncbi.nlm.nih.gov/books/NBK554560/