Question: what is the difference between penicillin and cephalosporin?
Answer: Cephalosporins are related to the structure and antimicrobial activity of penicillins. Both groups of antibiotics possess the core four-membered β-lactam ring. The β-lactam ring in penicillins is connected to a five-membered thiazolidine ring, or penam, and the side chain, R, differentiates the different penicillins.