"N-Acetylglucosamine (N-acetyl-D-glucosamine, or GlcNAc, or NAG) is a monosaccharide derivative of 
glucose. It is an amide between glucosamine and acetic acid. It has a molecular formula of C8H15NO6, a molar mass of 221.21 g/mol, and it is significant in several biological systems."
"It is part of a biopolymer in the bacterial cell wall, built from alternating units of GlcNAc and N-acetylmuramic acid (MurNAc), cross-linked with oligopeptides at the lactic acid residue of MurNAc. This layered structure is called peptidoglycan."
"GlcNAc is the monomeric unit of the polymer chitin, which forms the outer coverings of insects and crustaceans."