Penicillin’s mode of action is to inhibit Choose one: A. DNA replication by allosterically binding to DNA polymerase. B. translation by binding to the 50S ribosomal subunit. C. cell wall cross-link formation. D. translation by binding to the 30S ribosomal subunit.

C. cell wall cross-link formation

Explanation:

Penicillin is an antibiotic that kills the bacteria by inhibiting the enzyme that catalyzes the formation of peptide cross-links between N- acetyl glucosamine and N-acetylmuramic acid of peptidoglycan of a bacterial cell wall. The enzyme is called transpeptidase. These cross-links hold the sheets of these monomers and form the rigid peptidoglycan layer.

In the absence of the cross-links, Gram-positive bacteria completely lose the cell wall and become protoplast while the Gram-negative bacterial cells remain covered with the outer membrane alone. These bacterial cells lyse when placed in a hypotonic solution.

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