This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Penicillin & Cephalosporin, Subject name: Pharmacology
The mechanism of action of cephalosporin is: 
Select and explain. 
A. Interferes with cell wall synthesis, B. Inhibition ol DNA gyrase, C. Inhibition of protein synthesis, D. Inhibition of DMA polymerase
A: Interferes with cell wall synthesis
Answer: A: Interferes with cell wall synthesis 
Explanation: Ans: A (Interferes with cell wall synthesis) Ref: Goodman & Gilmans The Pharmacological Basis of Therapeutics, 12th ed, 2011. Pg 1479, 1493: Basic and Clinical Pharmacology by Katzung, 2012, 12th ed, Pg 792Explanation:Cephalosporin inhibits bacterial cell wall synthesis.Its mechanism of action is similar to penicillin as both are beta lactams.Bacterial ceil wall plays a major role in the growth and development of bacteria.Peptidoglycan. a component of bacterial cell wall owing to its cross-linked structure offers strength to the cell wall.Peptidoglycan is composed of N-acetyl- glucosamine and N-acetylmuramic acid with cross-linking.A five amino acid peptide known as pentapeptide is linked to N-acetylmuramic acid and this peptide terminates as D-alanyl-D- alanine.Penicillin Binding Protein (PBP) removes terminal alanine from D-alanyl -D-alanine and forms cross link with the adjacent peptide, thus enhancing cell wall rigidity.Beta lactam antibiotics are structurally similar to D-alanyl -D-alanine, and hence covalently bind to PBP, resulting in inhibition of transpeptidation reaction w hich is essential for the removal of D-alanine from D-alanyl-D- alanine.As peptidoglycan synthesis is inhibited by cephalosporins as any other beta lactams, the bacterial cell dies. However cell death is maximum when the cells are actively growing and synthesizing cell wall.