Penicillin is both the name of a historically important antibiotic and, in modern usage, a family of related medicines. This lesson introduces where penicillins come from, how the name is used, and how natural and semisynthetic types are grouped.
Penicillins are a group of β-lactam antibiotics originally obtained from Penicillium moulds, especially P. chrysogenum and P. rubens. Fleming coined the word penicillin in 1929 after observing antibacterial activity in a mould culture. The name reflects the genus Penicillium, just as a substance named digitalin was named after the plant genus Digitalis.
All flashcards
Why was the antimicrobial substance named penicillin?
Alexander Fleming coined the name from *Penicillium*, the mould genus associated with its antibacterial activity.
Which natural penicillins are in routine clinical use?
Penicillin G and penicillin V; G is generally injected, while V can be taken by mouth.
What is 6-APA used for in penicillin development?
It provides a core structure to which different side chains can be attached to make semisynthetic penicillins.
How does penicillin interfere with bacterial cell-wall construction?
It inactivates penicillin-binding proteins, blocking the formation of peptidoglycan cross-links.
How can β-lactamases confer resistance to penicillin?
They hydrolyse and open the β-lactam ring, impairing the antibiotic's activity.
Quiz questions
What structural feature of penicillin helps it bind to penicillin-binding proteins?Answer: Its β-lactam ring resembles the D-alanine-D-alanine portion of a peptidoglycan building block.
What enables MRSA to continue cell-wall synthesis despite many β-lactam antibiotics?Answer: It produces PBP2a, a penicillin-binding protein with poor affinity for penicillin.
How can probenecid prolong penicillin activity in certain situations?Answer: It competitively reduces the kidneys' excretion of penicillin.
In which year did Alexander Fleming observe mould-associated bacterial killing?Answer: 1928
How can penicillins cross the outer membrane of Gram-negative bacteria?Answer: They can pass through porins, with entry affected by drug size and porin properties.
Based on the Wikipedia article Penicillin, licensed CC BY-SA 4.0. Adapted into a summary, flashcards and quizzes.