Difference between revisions of "Chitin" - New World Encyclopedia
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'''Chitin''' is a hard, semitransparent [[carbohydrate#polysaccharides|polysaccharide]] that is found in main places in the natural world, including serving as the main component of arthropod exoskeletons and the cell walls of some fungi. | '''Chitin''' is a hard, semitransparent [[carbohydrate#polysaccharides|polysaccharide]] that is found in main places in the natural world, including serving as the main component of arthropod exoskeletons and the cell walls of some fungi. | ||
| − | Chitin, for example, is the main component of the shells of [[crustacean]]s, such as [[crab]]s, [[lobster]]s, and [[shrimp]], and many [[insect]]s, such as [[ant]]s and [[beetle]]s, have a covering made from chitin. Chitin is found in the cell walls of some [[mold]]s and [[ | + | Chitin, for example, is the main component of the shells of [[crustacean]]s, such as [[crab]]s, [[lobster]]s, and [[shrimp]], and many [[insect]]s, such as [[ant]]s and [[beetle]]s, have a covering made from chitin. Chitin is found in the cell walls of some [[mold]]s, [[yeast]], and [[algae]]. It also comprises parts of the jaws and body spines of certain worms (Nicol 1991). |
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| + | Chitin also has several medical and industrial uses, including use as a [[surgery|surgical thread]]. | ||
==Detailed Description== | ==Detailed Description== | ||
| − | '''Chitin''' | + | '''Chitin''' is a [[carbohydrate#polysaccharides|polysaccharide]] that 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]], which forms the primary structural component of green [[plant]]s. |
| − | In effect chitin may be described as [[cellulose]] with one hydroxyl group on each [[ | + | In effect chitin may be described as [[cellulose]] with one hydroxyl group on each [[carbohydrate|monomer]] replaced by an acetylamine group. This allows for increased hydrogen bonding between adjacent polymers, giving the polymer increased strength. Both cellulose and chitin are long unbranched chains of [[glucose]] derivatives, and both materials contribute structure and strength, protecting the organisms (plants in the case of cellulose). Both are common; cellulose is by far the most abundant organic (carbon-containing) compound on Earth. |
In its unmodified form, chitin is translucent, pliable, and resilient, and quite tough. In [[arthropod]]s, however, it is frequently modified by being embedded in a hardened proteinaceous matrix, which forms much of the hard exoskeleton. The difference between unmodified and modified chitinous exoskeleton can be seen by comparing the soft body wall of a [[caterpillar]] to a [[beetle]]'s hard body covering. | In its unmodified form, chitin is translucent, pliable, and resilient, and quite tough. In [[arthropod]]s, however, it is frequently modified by being embedded in a hardened proteinaceous matrix, which forms much of the hard exoskeleton. The difference between unmodified and modified chitinous exoskeleton can be seen by comparing the soft body wall of a [[caterpillar]] to a [[beetle]]'s hard body covering. | ||
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Chitin is closely related to chitosan (a more water-soluble derivative of chitin). | Chitin is closely related to chitosan (a more water-soluble derivative of chitin). | ||
| − | == | + | ==History and etymology== |
| − | + | In 1821, Henri Braconnot, director of the botanical garden in Nancy, France, noticed that there was a material in [[mushroom]]s that did not dissolve in [[sulfuric acid]]. | |
| + | He called it fungine (Nicol 1991). | ||
| − | + | 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." 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".[http://bartelby.com/61/7/C0310700.html American Heritage dictionary of the English Language: Fourth Edition. 2000. Entry for chiton] | |
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| − | + | A similar word, "chiton," refers to a marine animal with a protective shell (also known as a sea cradle). | |
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| − | == | + | ==Uses== |
| − | Chitin's properties as a | + | Chitin's properties as a tough and strong material make it favorable as [[Surgery|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 [[human]]s. Therefore, chitin is used as a wound-healing agent. | + | Chitin also has some unusual properties in that it accelerates healing in wounds in [[human]]s. Therefore, chitin is used as a wound-healing agent. It is also used in development of an artificial skin that the body does not reject (Towle 1989). |
| + | 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, and industrial separation membranes are made from chitin. Processes to size and strengthen paper also employ chitin. Chitin may also be used to make varnish, a seed coating to protect against [[fungus]], and specialized contact lenses (Towle 19890. | ||
==References== | ==References== | ||
| − | + | * Nicol, S. 1991. 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. ''New Scientist'' 1755(February 09, 1991). | |
| + | * Towle, A. 1989. ''Modern Biology''. Austin, TX: Holt, Rinehart and Winston. ISBN: 0-03-013919-8. | ||
== External links == | == External links == | ||
Revision as of 03:53, 23 December 2006
Chitin is a hard, semitransparent polysaccharide that is found in main places in the natural world, including serving as the main component of arthropod exoskeletons and the cell walls of some fungi.
Chitin, for example, is the main component of the shells of crustaceans, such as crabs, lobsters, and shrimp, and many insects, such as ants and beetles, have a covering made from chitin. Chitin is found in the cell walls of some molds, yeast, and algae. It also comprises parts of the jaws and body spines of certain worms (Nicol 1991).
Chitin also has several medical and industrial uses, including use as a surgical thread.
Detailed Description
Chitin is a polysaccharide that 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, which forms the primary structural component of green plants.
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. Both cellulose and chitin are long unbranched chains of glucose derivatives, and both materials contribute structure and strength, protecting the organisms (plants in the case of cellulose). Both are common; cellulose is by far the most abundant organic (carbon-containing) compound on Earth.
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 hard exoskeleton. The difference between unmodified and modified chitinous exoskeleton can be seen by comparing the soft body wall of a caterpillar to a beetle's hard body covering.
Chitin is an unusual substance as it is a naturally occurring polymer. Its breakdown is conducted by bacteria that are characterized by special chemical receptors to the sugars produced by 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).
History and etymology
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 (Nicol 1991).
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." 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".American Heritage dictionary of the English Language: Fourth Edition. 2000. Entry for chiton
A similar word, "chiton," refers to a marine animal with a protective shell (also known as a sea cradle).
Uses
Chitin's properties as a tough and strong material make it favorable 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. It is also used in development of an artificial skin that the body does not reject (Towle 1989).
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, and industrial separation membranes are made from chitin. Processes to size and strengthen paper also employ chitin. Chitin may also be used to make varnish, a seed coating to protect against fungus, and specialized contact lenses (Towle 19890.
ReferencesISBN links support NWE through referral fees
- Nicol, S. 1991. 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. New Scientist 1755(February 09, 1991).
- Towle, A. 1989. Modern Biology. Austin, TX: Holt, Rinehart and Winston. ISBN: 0-03-013919-8.
External links
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