d. The cell walls of bacteria are composed of peptidoglycan
Explanation:
Bacterial cell wall is made of peptidoglycan or murein. It is made of sugars and amino acids. Sugar component consists of N-acetylmuramic acid (NAM) and N-acetylglucosamine (NAG) alternating residues. A peptide chain of three to five amino acids is attached to NAM.
Gram positive bacteria have thick cell wall made of many peptidoglycan layers. Whereas gram negative bacteria have a thinner layer. The peptidoglycan cell wall is required for the survival of the bacteria hence it is targeted by many antibiotics like penicillin.
