Penicillins: Penicillin works by interfering with interpeptide linking of peptidoglycan, the strong, structural molecule found specifically in bacterial cell walls. The cell walls without intact peptidoglycan cross links are weak, prone to collapse and disintegrate when the bacteria attempts to divide. Since the eukaryotic cells of human beings do not have cell walls, our cells are not damaged by penicillin. For more about penicillin mode of action you can refer on the think quest website or visit your local doctor for more details.
Cephalosporins: Cephalosporins are a type of β-lactam antibiotic, and closely related to the penicillins. They are bactericidal, with the same MOA as other beta-lactams.
Cephalosporins disrupt synthesis of the peptidoglycan layer of bacterial cell walls. Peptidoglycan is a strong structural molecule specific to the cells walls of bacteria. With the cell wall structure compromised, the bactericidal result is lysis and death of the cell.
Our cells do not have cells walls or peptidoglycan, therefore, B-lactam antibiotics are able to target bacterial cells without harming human cells.
Chloramphenicols: Chloramphenicol is a bacteriostatic drug that stops bacterial growth by inhibiting protein synthesis. Chloramphenicol prevents protein chain elongation by inhibiting the peptidyl transferase activity of the bacterial ribosome. It specifically binds to A2451 and A2452 residues in the 23S rRNA of the 50S ribosomal subunit, preventing peptide bond formation. While chloramphenicol and the macrolide class of antibiotics both interact with ribosomes, chloramphenicol is not a macrolide. It directly interferes with substrate binding, whereas macrolides sterically block the progression of the growing peptide.
Tetracyclines: Tetracyclines exert their bacteriostatic effect by inhibiting protein synthesis in bacteria. This antibiotic prevents transfer-RNA (tRNA) molecules (a type of nucleic acids which transport amino acids) from...