Peptidoglycan is a polymer consisting of sugars and amino acids that form a mesh-like layer outside the plasma membrane of most bacteria. The sugar components consists of alternating residues of beta-(1-4) linked N-acetylglucosamine (NAG) and N- acetylmuramic acid (NAM). One chain of alternating of alternating NAGs and NAMs is connected to another chain via tetrapeptides composed of four amino acids and make up the "peptido" portion of peptidoglycan.