Written by the Fiveable Content Team • Last updated September 2025
Written by the Fiveable Content Team • Last updated September 2025
Definition
Penicillin is a group of antibiotics derived from Penicillium fungi. It is widely used to treat bacterial infections by inhibiting cell wall synthesis.
5 Must Know Facts For Your Next Test
Alexander Fleming discovered penicillin in 1928, revolutionizing the field of antimicrobial chemotherapy.
Penicillin works primarily by targeting and inhibiting the transpeptidase enzyme involved in bacterial cell wall synthesis.
It is particularly effective against Gram-positive bacteria such as Streptococcus and Staphylococcus species.
The development of penicillin marked the beginning of the antibiotic era and has saved countless lives since its introduction.
Resistance to penicillin can occur through the production of beta-lactamase enzymes, which break down the antibiotic.
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Related terms
Antibiotic: A substance that inhibits the growth of or destroys microorganisms.
Beta-lactamase: An enzyme produced by certain bacteria that deactivates beta-lactam antibiotics like penicillin.
Transpeptidase: An enzyme involved in bacterial cell wall synthesis targeted by penicillin.