Chitin
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Molecular formula: (C8H13NO5)n
Chitin is a hard, semitransparent material that's found in many places in the natural world. For example, chitin is the main component of the shells of crustaceans, such as the crab, lobster, and shrimp. Many insects, such as ants and beetles, have a covering made from chitin. Chitin is even found in the cell walls of some fungi, molds and yeast. It has several medical and industrial uses.
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[edit] Detailed Description
Chitin (IPA: [ˈkaɪtɪn]) is one of the main components in the cell walls of fungi, the exoskeletons of insects and other arthropods, and in some other animals. It is a polysaccharide; it is constructed from units of N-acetylglucosamine (more completely, N-acetyl-D-glucos-2-amine). These are linked together in β-1,4 fashion (in a similar manner to the glucose units which form cellulose). In effect chitin may be described as cellulose with one hydroxyl group on each monomer replaced by an acetylamine group. This allows for increased hydrogen bonding between adjacent polymers, giving the polymer increased strength.
In its unmodified form, chitin is translucent, pliable and resilient, and quite tough. In arthropods, however, it is frequently modified, by being embedded in a hardened proteinaceous matrix, which forms much of the exoskeleton. The difference between unmodified and modified chitinous exoskeleton can be seen by comparing the body wall of a caterpillar to a beetle, for example.
Chitin is an unusual substance as it is a naturally occurring polymer. Its breakdown is conducted by bacteria which have receptors to simple sugars from the decomposition of chitin. If chitin is detected they then produce enzymes to digest the chitin by reducing it to simple sugars and ammonia.
Chitin is closely related to chitosan (a more water-soluble derivative of chitin).
Chitin is also closely related chemically to cellulose, in that it is a long unbranched chain of glucose derivatives. Both materials contribute structure and strength, protecting the organism.
[edit] Etymology
The English word "chitin" comes from the French word "chitine", which first appeared in 1836. These words were derived from the Latin word "chitōn", meaning mollusk, which in turn comes from the Greek word khitōn , meaning "tunic" or "frock". A similar word, "chiton", refers to a marine animal with a protective shell (also known as a sea cradle). The Greek word "khitōn" can be traced to the Central Semitic word "*kittan", which is from the Akkadian words "kitû" or "kita’um", meaning flax or linen, and originally the Sumerian word "gada" or "gida".[1]
[edit] History
In 1821, Henri Braconnot, director of the botanical garden in Nancy, France, noticed that there was a material in mushrooms that did not dissolve in sulfuric acid. He called it fungine.[2]
[edit] Uses
[edit] Industrial
Chitin is used industrially in many different processes. For example, chitin is used in water and wastewater purification and to thicken and stabilize foods and pharmaceuticals. Chitin also acts as a binder in dyes, fabrics, and adhesives. Ion-exchange resins can be made from chitin. Industrial separation membranes are made from chitin. Processes to size and strengthen paper employ chitin.
[edit] Medicine
Chitin's properties as a tough, and strong material make it favourable as surgical thread. Its biodegradibility also means it wears away with time as the wound heals.
Chitin also has some unusual properties in that it accelerates healing in wounds in humans. Therefore, chitin is used as a wound-healing agent.
[edit] References
- ^ American Heritage dictionary of the English Language: Fourth Edition. 2000. entry for chiton
- ^ Life after death for empty shells: Crustacean fisheries create a mountain of waste shells, made of a strong natural polymer, chitin. Now chemists are helping to put this waste to some surprising uses, Stephen Nicol, New Scientist, Issue 1755, February 09, 1991.
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