Chitin (C Carbon is the chemical element with symbol C and atomic number 6. As a member of group 14 on the periodic table, it is nonmetallic and tetravalent—making four electrons available to form covalent chemical bonds. There are three naturally occurring isotopes, with 12C and 13C being stable, while 14C is radioactive, decaying with a half-life of₈H Hydrogen is the chemical element with atomic number 1. It is represented by the symbol H. With an average atomic weight of 1.00794 u (1.007825 u for Hydrogen-1), hydrogen is the lightest and most abundant chemical element, constituting roughly 75 % of the Universe's elemental mass. Stars in the main sequence are mainly composed of hydrogen in its₁₃O Oxygen (pronounced /ˈɒksɨdʒɨn/, OK-si-jin, from the Greek roots ὀξύς (acid, literally "sharp", from the taste of acids) and -γενής (-genēs) (producer, literally begetter), is the element with atomic number 8 and represented by the symbol O. It is a member of the chalcogen group on the periodic table, and is a highly₅N Nitrogen is a chemical element that has the symbol N, atomic number of 7 and atomic mass 14.00674 u. Elemental nitrogen is a colorless, odorless, tasteless and mostly inert diatomic gas at standard conditions, constituting 78.08% by volume of Earth's atmosphere)_n (pronounced /ˈkaɪtɨn/) is a long-chain polymer A polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a wide variety of properties of a N-acetylglucosamine N-Acetylglucosamine is a monosaccharide derivative of glucose. It is an amide between glucosamine and acetic acid. It has a molecular formula of C8H15N , a derivative of glucose, and is found in many places throughout the natural world. It is the main component of the cell walls A cell wall is a tough, usually flexible but sometimes fairly rigid layer that surrounds some types of cells. It is located outside the cell membrane and provides these cells with structural support and protection, and also acts as a filtering mechanism. A major function of the cell wall is to act as a pressure vessel, preventing over-expansion of fungi A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds, as well as the more familiar mushrooms. The Fungi (pronounced /ˈfʌndʒaɪ/ or /ˈfʌŋɡaɪ/) are classified as a kingdom that is separate from plants, animals and bacteria. One major difference is that fungal cells have cell, the exoskeletons An exoskeleton is an external skeleton that supports and protects an animal's body, in contrast to the internal skeleton of, for example, a human. Some animals, such as the tortoise, have both an endoskeleton and an exoskeleton. In popular usage, many of the larger kinds of exoskeletons are known as "shells" of arthropods An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the Phylum Arthropoda (from Greek ἄρθρον arthron, "joint", and ποδός podos "foot", which together mean "jointed feet"), and include the insects, arachnids, crustaceans, and such as crustaceans Crustaceans form a very large group of arthropods, usually treated as a subphylum, which includes such familiar animals as crabs, lobsters, crayfish, shrimp, krill and barnacles. The 50,000 described species range in size from Stygotantulus stocki at 0.1 mm (0.004 in), to the Japanese spider crab with a leg span of up to 14 ft (4.3 m) and a mass (e.g. crabs True crabs are decapod crustaceans of the infraorder Brachyura, which typically have a very short projecting "tail" , or where the reduced abdomen is entirely hidden under the thorax. Other animals, such as hermit crabs, king crabs, porcelain crabs, horseshoe crabs and crab lice, are not true crabs, lobsters Clawed lobsters comprise a family of large marine crustaceans. Lobsters are economically important as seafood, forming the basis of a global industry that nets more than US$1 billion annually and shrimps Shrimp are swimming, decapod crustaceans classified in the infraorder Caridea, found widely around the world in both fresh and salt water. Adult shrimp are filter feeding benthic animals living close to the bottom. They can live in schools and can swim rapidly backwards. Shrimp are an important food source for larger animals from fish to whales) and insects Insects are a class within the arthropods that have a chitinous exoskeleton, a three-part body (head, thorax, and abdomen), three pairs of jointed legs, compound eyes, and two antennae. They are among the most diverse group of animals on the planet and include more than a million described species and represent more than half of all known living, the radulas The radula is an anatomical structure found in mollusks and used for feeding. It is a minutely toothed, chitinous ribbon. It is typically used for scraping or cutting food before the food enters the esophagus. The radula is unique to the molluscs, and is found in all classes of mollusks except for the bivalves of mollusks The Mollusca, common name molluscs or mollusks,[note 1] is a large phylum of invertebrate animals. There are around 85,000 recognized extant species of molluscs. This is the largest marine phylum, comprising about 23% of all the named marine organisms. Numerous molluscs also live in freshwater and terrestrial habitats. Molluscs are highly diverse, and the beaks of cephalopods A cephalopod (Greek plural Κεφαλόποδα ; "head-feet") is any member of the mollusc class Cephalopoda, characterized by bilateral body symmetry, a prominent head, and a modification of the mollusk foot, a muscular hydrostat, into the form of arms or tentacles. Teuthology, a branch of malacology, is the study of cephalopods. These, including squid Squid are marine cephalopods of the order Teuthida, which comprises around 300 species. Like all other cephalopods, squid have a distinct head, bilateral symmetry, a mantle, and arms. Squid, like cuttlefish, have eight arms arranged in pairs and two longer tentacles and octopuses The octopus is a cephalopod mollusk in the order Octopoda. Octopuses have two eyes and four pairs of arms, and like other cephalopods they are bilaterally symmetric. An octopus has a hard beak, with its mouth at the center point of the arms. Most octopuses have no internal or external skeleton, allowing them to squeeze through tight places. Chitin may be compared to the polysaccharide cellulose Cellulose is an organic compound with the formula n, a polysaccharide consisting of a linear chain of several hundred to over ten thousand β(1→4) linked D-glucose units and to the protein keratin Keratin refers to a family of fibrous structural proteins. Keratin is the key structural material making up the outer layer of human skin. It is also the key structural component of hair and nails. Keratin monomers assemble into bundles to form intermediate filaments, which are tough and insoluble and form strong unmineralized tissues found in. Although keratin is a protein, and not a carbohydrate A carbohydrate is an organic compound with the general formula Cmn, that is, consists only of carbon, hydrogen and oxygen, with the last two in the 2:1 atom ratio. Carbohydrates can be viewed as hydrates of carbon, hence their name. Structurally however, it is more accurate to view them as polyhydroxy aldehydes and ketones like chitin, keratin and chitin have similar structural functions. Chitin has also proven useful for several medical and industrial purposes.

Etymology

The English word "chitin" comes from the French French is a Romance language spoken as a first language by about 136 million people worldwide. Around 190 million people speak French as a second language, and an additional 200 million speak it as an acquired foreign language. French speaking communities are present in 57 countries and territories. Most native speakers of the language live in word "chitine", which first appeared in 1836. These words were derived from the Greek Greek , an independent branch of the Indo-European family of languages, is the language of the Greeks. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. In its ancient form, it is the language of classical ancient Greek literature and the New Testament of word "chitōn", meaning mollusk The Mollusca, common name molluscs or mollusks,[note 1] is a large phylum of invertebrate animals. There are around 85,000 recognized extant species of molluscs. This is the largest marine phylum, comprising about 23% of all the named marine organisms. Numerous molluscs also live in freshwater and terrestrial habitats. Molluscs are highly diverse,. That is either influenced by, or related to the Greek Greek , an independent branch of the Indo-European family of languages, is the language of the Greeks. Native to the southern Balkans, it has the longest documented history of any Indo-European language, spanning 34 centuries of written records. In its ancient form, it is the language of classical ancient Greek literature and the New Testament of word khitōn A chiton was a form of clothing worn by men and women in Ancient Greece, from the Archaic period (c. 750–c. 500 BC) to the Hellenistic period (323–30 BC). There are two forms of chiton, the Doric chiton and the later Ionic chiton. The "Doric" style was simpler and had no "sleeves", being simply pinned, sewn, or buttoned at, meaning "tunic A tunic is any of several types of clothing for the body, of various lengths reaching from the shoulders to somewhere between the hips and the ankles. The name derives from the Latin tunica commonly worn by both men and women in Ancient Rome, which in turn is based on earlier Greek garments" or "frock Frock has been used since Middle English as the name for an article of clothing for men and women", the Central Semitic In linguistics and ethnology, Semitic was first used to refer to a language family of largely Middle Eastern origin, now called the Semitic languages. This family includes the ancient and modern forms of Akkadian, Amharic, Arabic, Aramaic, Ge'ez, Hebrew, Maltese, Phoenician, Tigre and Tigrinya among others word "*kittan", the Akkadian Akkadian (also Accadian, Assyro-Babylonian) is an extinct Semitic language (part of the greater Afroasiatic language family) that was spoken in ancient Mesopotamia. The earliest attested Semitic language, it used the cuneiform writing system derived ultimately from ancient Sumerian, an unrelated language isolate. The name of the language is words "kitû" or "kita’um", meaning flax Flax (binomial name: Linum usitatissimum) is a member of the genus Linum in the family Linaceae. It is native to the region extending from the eastern Mediterranean to India and was probably first domesticated in the Fertile Crescent. This is called as Agasi/Akshi in Kannada, जवस (Jawas/Javas) or अळशी (Alashi) in Marathi and तीस or linen Linen is a textile made from the fibers of the flax plant, Linum usitatissimum. Linen is labor-intensive to manufacture, but when it is made into garments, it is valued for its exceptional coolness and freshness in hot weather, and the Sumerian Sumerian was the language of ancient Sumer, spoken in southern Mesopotamia (modern Iraq) since at least the 4th millennium BCE. During the third millennium BCE, there developed a very intimate cultural symbiosis between the Sumerians and the Akkadians, which included widespread bilingualism. The influence of Sumerian on Akkadian (and vice versa) word "gada" or "gida".^[1]

A similar word, "chiton Chitons are small to large, primitive marine molluscs in the class Polyplacophora. There are 900 to 1,000 extant species of chitons in the class, which was formerly known as Amphineura", refers to a marine animal with a protective shell (also known as a "sea cradle").

Chemistry, physical properties and biological function

Chitin is a modified polysaccharide Polysaccharides are polymeric carbohydrate structures, formed of repeating units joined together by glycosidic bonds. These structures are often linear, but may contain various degrees of branching. Polysaccharides are often quite heterogeneous, containing slight modifications of the repeating unit. Depending on the structure, these macromolecules which contains nitrogen; it is synthesized Biosynthesis is an enzyme-catalyzed process in cells of living organisms by which substrates are converted to more complex products. The biosynthesis process often consists of several enzymatic steps in which the product of one step is used as substrate in the following step. Examples for such multi-step biosynthetic pathways are those for the from units of N-acetylglucosamine N-Acetylglucosamine is a monosaccharide derivative of glucose. It is an amide between glucosamine and acetic acid. It has a molecular formula of C8H15N (more precisely, 2-(acetylamino)-2-deoxy-D-glucose). These units form covalent β-1,4 linkages (similar to the linkages between glucose Glucose , a simple sugar (monosaccharide), is an important carbohydrate in biology. Cells use it as a source of energy and a metabolic intermediate. Glucose is one of the main products of photosynthesis and starts cellular respiration. Starch and cellulose are polymers derived from the dehydration of glucose. The name "glucose" comes units forming cellulose Cellulose is an organic compound with the formula n, a polysaccharide consisting of a linear chain of several hundred to over ten thousand β(1→4) linked D-glucose units). Chitin may therefore be described as cellulose Cellulose is an organic compound with the formula n, a polysaccharide consisting of a linear chain of several hundred to over ten thousand β(1→4) linked D-glucose units with one hydroxyl In chemistry, hydroxyl is a compound containing an oxygen atom bound covalently with a hydrogen atom. The neutral form of this group is a hydroxyl radical. The hydroxyl anion is called hydroxide; it is a diatomic ion with a single negative electronic charge. In discussions of synthetic methods in organic chemistry the hydroxyl group (–OH) is group on each monomer A monomer is an atom or a small molecule that may bind chemically to other monomers to form a polymer or cluster[citation needed]. The most common natural monomer is glucose, which is linked by glycosidic bonds into polymers such as cellulose and starch, and is over 76% of the weight of all plant matter substituted with an acetyl In organic chemistry, acetyl is a functional group, the acyl with chemical formula C amine Amines are organic compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are derivatives of ammonia, wherein one or more hydrogen atoms have been replaced by a substituent such as an alkyl or aryl group. Important amines include amino acids, biogenic amines, trimethylamine, and aniline; see Category:Amines for group. This allows for increased hydrogen bonding A hydrogen bond is the attractive interaction of a hydrogen atom with an electronegative atom, such as nitrogen, oxygen or fluorine . The hydrogen must be covalently bonded to another electronegative atom to create the bond. These bonds can occur between molecules (intermolecularly), or within different parts of a single molecule (intramolecularly) between adjacent polymers A polymer is a large molecule composed of repeating structural units typically connected by covalent chemical bonds. While polymer in popular usage suggests plastic, the term actually refers to a large class of natural and synthetic materials with a wide variety of properties, giving the chitin-polymer matrix increased strength.

In its unmodified form, chitin is translucent, pliable, resilient and quite tough. In arthropods An arthropod is an invertebrate animal having an exoskeleton , a segmented body, and jointed appendages. Arthropods are members of the Phylum Arthropoda (from Greek ἄρθρον arthron, "joint", and ποδός podos "foot", which together mean "jointed feet"), and include the insects, arachnids, crustaceans, and, however, it is often modified, becoming embedded in a hardened proteinaceous matrix, which forms much of the exoskeleton. In its pure form it is leathery, but when encrusted in calcium carbonate it becomes much harder.^[2] The difference between the unmodified and modified forms can be seen by comparing the body wall of a caterpillar (unmodified) to a beetle (modified).

Fossil record

Chitin first appeared in the exoskeletons of Cambrian arthropods, e.g. trilobites. The oldest preserved chitin dates to the Oligocene, about 25 million years ago.^[3]

Uses

Agriculture

Most recent studies point out that chitin is a good inducer for defense mechanisms in plants.^[4] It was recently tested as a fertilizer that can help plants develop healthy immune responses, and have a much better yield and life expectancy.^[5] The EPA regulates chitin for agricultural use within the USA.^[6] Chitosan is derived from chitin, which is used as a biocontrol elicitor in agriculture and horticulture.

Industrial

Chitin is used industrially in many processes. It is used as an additive to thicken and stabilize foods and pharmaceuticals. It 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.^{[citation needed]}

Medicine

Chitin's properties as a flexible and strong material make it favorable as surgical thread. Its biodegradibility means it wears away with time as the wound heals. Moreover, chitin has some unusual properties that accelerate healing of wounds in humans.^[7]

Occupations associated with high environmental chitin levels, such as shellfish processors, are prone to high incidences of asthma. Recent studies have suggested that chitin may play a role in a possible pathway in human allergic disease. Specifically, mice treated with chitin develop an allergic response, characterized by a build-up of interleukin-4 expressing innate immune cells. In these treated mice, additional treatment with a chitinase enzyme abolishes the response.^[8]

See also

• Chitosan (Natural Biocontrol for Agricultural & Horticultural use)
• Chitobiose
• Biopesticide

References

1. ^ American Heritage dictionary of the English Language: Fourth Edition. 2000. entry for chiton
2. ^ Campbell, N. A. (1996) Biology (4th edition) Benjamin Cummings, New Work. p.69 ISBN 0-8053-1957-3
3. ^ Briggs, DEG (29 January 1999). "Molecular taphonomy of animal and plant cuticles: selective preservation and diagenesis". Philosophical Transactions of the Royal Society B: Biological Sciences 354 (1379): 7–17. doi:10.1098/rstb.1999.0356.
4. ^ "Linden, J., Stoner, R., Knutson, K. Gardner-Hughes, C. “Organic Disease Control Elicitors”. Agro Food Industry Hi-Te (p12-15 Oct 2000)". http://www.yeacrops.com/Crop%20Protection%20Article.pdf.
5. ^ "Chitosan derived from chitin, Chitosan Natural Biocontrol for Agricutlural & Horticultural use". http://en.wikipedia.org/wiki/Chitosan#Agricultural_.26_Horticultural_use.
6. ^ "EPA: Chitin; Poly-N-acetyl-D-glucosamine (128991) Fact Sheet". http://www.epa.gov/pesticides/biopesticides/ingredients/factsheets/factsheet_128991.htm.
7. ^ Bhuvanesh Gupta,Abha Arorab,Shalini Saxenaa and Mohammad Sarwar Alam (July 2008). "Preparation of chitosan–polyethylene glycol coated cotton membranes for wound dressings: preparation and characterization". Polymers for Advanced Technologies 20: 58–65. doi:10.1002/pat.1280. http://www3.interscience.wiley.com/cgi-bin/fulltext/121487185/PDFSTART. </
8. ^ Tiffany A. Reese, Hong-Erh Liang, Andrew M. Tager, Andrew D. Luster, Nico Van Rooijen, David Voehringer & Richard M. Locksley (3 May 2007). "Chitin induces accumulation in tissue of innate immune cells associated with allergy". Nature 447 (7140): 92–96. doi:10.1038/nature05746. PMID 17450126. PMC 2527589. http://www.nature.com/nature/journal/v447/n7140/edsumm/e070503-13.html.

• Martín-Gil FJ, Leal JA, Gómez-Miranda B, Martín-Gil J, Prieto A, Ramos-Sánchez MC. "Low temperature thermal behaviour of chitins and chitin-glucans". Thermochim. Acta, 1992, vol. 211, pp. 241–254.

External links

• Horseshoe Crab Chitin Research
• Information about Chitin (Heppe Medical Chitosan)
• MeSH Chitin
• Chitin Product Information from China GreatVista Chemicals

Categories: Biomolecules | Polysaccharides | Acetamides

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