Description: Cellulose-like biopolymer consisting predominantly of unbranched chains of b-(1->4)-2-acetamido-2-deoxy-D-glucose (also named N-acetyl-D-glucosamine) residues. Found in fungi, yeasts, marine invertebrates and arthropods, where it is a principal component in the exoskeletons. May be regarded as a derivative of cellulose, in which the C-2 hydroxyl groups have been replaced by acetamido residues