Final answer:
Beta-lactam antibiotics, including penicillin and cephalosporins, contain a beta-lactam ring essential for inhibiting bacterial cell wall synthesis.
Step-by-step explanation:
The correct answer to which antibiotics are beta-lactams is Penicillin and cephalosporins. Beta-lactam antibiotics are a class of antibiotics that include penicillins, cephalosporins, carbapenems, and monobactams, all of which contain a beta-lactam ring in their molecular structures. This ring is essential for their antibacterial activity as they inhibit cell wall synthesis by binding to penicillin-binding proteins (PBPs). Penicillin, the first antibiotic discovered, and cephalosporins both contain a beta-lactam ring and disrupt cell wall synthesis in bacteria, making them effective against various bacterial infections.