Chemistry:Chitin

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Short description: Long-chain polymer of a N-acetylglucosamine
Structure of the chitin molecule, showing two of the N-acetylglucosamine units that repeat to form long chains in β-(1→4)-linkage.
Haworth projection of the chitin molecule.
A close-up of the wing of a leafhopper; the wing is composed of chitin.

Chitin (C8H13O5N)n (/ˈkaɪtɪn/ KY-tin) is a long-chain polymer of N-acetylglucosamine, an amide derivative of glucose. Chitin is the second most abundant polysaccharide in nature (behind only cellulose); an estimated 1 billion tons of chitin are produced each year in the biosphere.[1] It is a primary component of cell walls in fungi (especially filamentous and mushroom forming fungi), the exoskeletons of arthropods such as crustaceans and insects, the radulae, cephalopod beaks and gladii of molluscs and in some nematodes and diatoms.[2][3] It is also synthesised by at least some fish and lissamphibians.[4] Commercially, chitin is extracted from the shells of crabs, shrimps, shellfish and lobsters, which are major by-products of the seafood industry.[2][3] The structure of chitin is comparable to cellulose, forming crystalline nanofibrils or whiskers. It is functionally comparable to the protein keratin. Chitin has proved useful for several medicinal, industrial and biotechnological purposes.[3][5]

Etymology

The English word "chitin" comes from the French word chitine, which was derived in 1821 from the Greek word χιτών (khitōn) meaning covering.[6]

A similar word, "chiton", refers to a marine animal with a protective shell.

Chemistry, physical properties and biological function

Chemical configurations of the different monosaccharides (glucose and N-acetylglucosamine) and polysaccharides (chitin and cellulose) presented in Haworth projection

The structure of chitin was determined by Albert Hofmann in 1929. Hofmann hydrolyzed chitin using a crude preparation of the enzyme chitinase, which he obtained from the snail Helix pomatia.[7][8][9]

Chitin is a modified