(pěp'tĭ-dō-glī'kən)

noun

A polymer which forms a mesh like layer outside the plasma membrane of most bacteria but not archaea, forming a cell wall. Structurally, peptidoglycan is a chain of alternating N-acetylglucosamine and N-acetylmuramic acid residues. Additionally, each N-acetylmuramic acid has a short chain of amino acids attached to it which link to each other forming "cross links" between chains. The exact structure of the cell wall varies amongst bacteria (see Gram-type-positive & Gram-type-negative).