Penicillin inhibits synthesis of bacterial

Penicillin, the first antibiotic discovered by Alexander Fleming, belongs to the ̢-lactam class of drugs [1]. Its primary mechanism of action involves the inhibition of bacterial cell wall synthesis [3]. Specifically, penicillin targets and binds to penicillin-binding proteins (PBPs), which are transpeptidase enzymes responsible for the final step of cell wall biosynthesis: the cross-linking of peptidoglycan layers [3]. By irreversibly binding to these enzymes, penicillin prevents the formation of a stable peptidoglycan mesh, which is essential for the structural integrity and maintenance of the bacterial cell wall [4]. This disruption makes the bacteria highly susceptible to osmotic lysis, leading to cell death [4]. Unlike bacteria, human cells do not possess a cell wall or peptidoglycan, which allows penicillin to exhibit selective toxicity against bacterial pathogens without harming the host [3].

Sources

1. [1] Science ,Class VIII . NCERT(Revised ed 2025) > Chapter 3: Health: The Ultimate Treasure > Discovery of the first antibiotic, Penicillin > p. 40
2. [3] https://pubmed.ncbi.nlm.nih.gov/7372662/
3. [2] https://www.sciencedirect.com/topics/medicine-and-dentistry/penicillin-binding-protein
4. [4] https://www.ncbi.nlm.nih.gov/books/NBK554560/