Chitin


Chitin (C8H13O5)n is a long-chain polymeric polysaccharides of beta-glucose that forms a hard, semitransparent material found throughout the natural world. Chitin is the main component of the cell walls of fungi, and in the exoskeltons of arthropods, such as the crustaceans (e.g. crab, lobster, and shrimp), and the insects (e.g. ants, beetles, mealworms, and butterflies). Chitin has also proven useful for several medical and industrial purposes.

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 the unmodified and modified forms can be seen by comparing the body wall of a squishy caterpillar (unmodified) to a beetle (modified).

Chitin is one of the many naturally occurring polymers. Its breakdown may be catalyzed by enzymes called chitinases, secreted by microorganisms such as bacteria, which may 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). It 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.

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 "kit" or "kitaum", meaning flax or linen, and originally the Sumerian word "gada" or "gida".[1]

Uses

Industrial

Chitin is used industrially in many different processes. Chitin is used in water and wastewater purification, and as an additive to thicken and stabilize foods and pharmaceuticals. Chitin also acts as a binder in dyes, fabrics, and adhesives. Industrial separation membranes and ion-exchange resins can be made from chitin. Processes to size and strengthen paper employ chitin.

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. Moreover, chitin has some unusual properties that accelerate healing in wounds in humans. Chitin has even been used as a stand-alone wound-healing agent.

References

  1. American Heritage dictionary of the English Language: Fourth Edition. 2000. entry for chiton
  2. 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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Last Edited March 5, 2007



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