Penicillin là một trong những thuốc kháng sinh trong một lớp học được gọi là thuốc kháng sinh beta-lactam. Lớp này được đặt tên cho cấu trúc vòng tròn tạo thành một phần của phân tử kháng sinh. Các lớp học khác của thuốc kháng sinh tetracycline, aminoglycoside, rifamycins, quinolone, và sulphonamide | compounds involves screening samples against bacteria for an inhibition in growth of the bacteria. In commercial settings such screening has been automated so that thousands of samples can be processed each day. Antibiotics can also be manufactured by tailoring a compound to hone in on a selected target. The advent of molecular sequencing technology and three-dimensional image reconstruction has made the design of antibiotics easier. Penicillin is one of the antibiotics in a class known as beta-lactam antibiotics. This class is named for the ring structure that forms part of the antibiotic molecule. Other classes of antibiotics include the tetracyclines aminoglycosides rifamycins quinolones and sulphonamides. The action of these antibiotics is varied. For example beta-lactam antibiotics exert their effect by disrupting the manufacture of peptidoglycan which is main stress-bearing network in the bacterial cell wall. The disruption can occur by blocking either the construction of the subunits of the peptidoglycan or by preventing their incorporation into the existing network. In another example amonglycoside antibiotics can bind to a subunit of the ribosome which blocks the manufacture of protein or can reduce the ability of molecules to move across the cell wall to the inside of the bacterium. As a final example the quinolone antibiotics disrupt the function of an enzyme that uncoils the double helix of deoxyribonucleic acid which is vital if the DNA is to be replicated. Besides being varied in their targets for antibacterial activity different antibiotics can also vary in the range of bacteria they affect. Some antibiotics are classified as narrow-spectrum antibiotics. They are lethal against only a few types or genera of bacteria. Other antibiotics are active against many bacteria whose construction can be very different. Such antibiotics are described as having a broad-spectrum of activity. In the decades following the discovery of penicillin a myriad of .
