chitin

chitin , main constituent of the shells of arthropods. Chitin, a polysaccharide (see carbohydrate ) analogous in chemical structure to cellulose , consists of units of a glucose derivative ( N -acetyl- d -glucosamine) joined to form a long, unbranched chain. Like cellulose, chitin contributes strength and protection to the organism. In arthropods the chitinous shell, or exoskeleton, covers the surface of the body, does not grow, and is periodically cast off (molted). After the old shell is shed, a new, larger shell is secreted by the epidermis, providing room for future growth. The chitin is rigid except between some body segments and joints where it is thin and allows movement of adjacent parts. Chitin is also found in the cell walls of some fungi.

chitin A polysaccharide comprising chains of N-acetyl-D-glucosamine, a derivative of glucose. Chitin is structurally very similar to cellulose and serves to strengthen the supporting structures of various invertebrates. It also occurs in fungi.

chitin Hard, tough substance that occurs widely in nature, particularly in the shells (exoskeletons) of arthropods such as crabs, insects and spiders. The walls of hyphae (microscopic tubes of fungi) are composed of slightly different chitin. Chemically chitin is a polysaccharide, derived from glucose.