Penicillin (Formula:C9H11N2O4S) inhibits synthesis of bacterial cell wall. It is an antibiotic first discovered by Alexander Fleming in 1929. It attacks the bacterial parasites by inhibiting protein synthesis and synthesis of the bacterial cell wall. The process, in turn, inhibits the growth and multiplication of bacteria. Penicillin is a group of antibiotics which include penicillin G, penicillin V, procaine penicillin, and benzathine penicillin.