polysaccharide


polysaccharide
/pol'ee sak"euh ruyd', -rid/, n. Chem.
a carbohydrate, as starch, inulin, or cellulose, containing more than three monosaccharide units per molecule, the units being attached to each other in the manner of acetals, and therefore capable of hydrolysis by acids or enzymes to monosaccharides.
Also, polysaccharose /pol'ee sak"euh rohs'/.
[1890-95; POLY- + SACCHARIDE]

* * *

Any of a large class of long-chain sugars composed of monosaccharides.

Because the chains may be unbranched or branched and the monosaccharides may be of one, two, or occasionally more kinds, polysaccharides can be categorized in various ways. Cellulose, starch, glycogen, and dextran are all polysaccharides of glucose, with different configurations. Pectins are composed of a galactose derivative, chitin of a glucose derivative. Connective tissues, joint fluid, and cartilage contain two-component polysaccharides, including heparin. See also oligosaccharide.

* * *

also called  glycan 
 the form in which most natural carbohydrates occur. Polysaccharides may have a molecular structure that is either branched or linear. Linear compounds such as cellulose often pack together to form a rigid structure; branched forms (e.g., gum arabic) generally are soluble in water and make pastes.

      Polysaccharides composed of many molecules of one sugar or one sugar derivative are called homopolysaccharides (homoglycans). Homopolysaccharides composed of glucose include glycogen and starch, the storage carbohydrates of animals and plants respectively; and cellulose (q.v.), the important structural component of most plants. Preparations of dextran, a glucose homopolysaccharide found in slimes secreted by certain bacteria, are used as substitutes for blood plasma in treating shock. Other homopolysaccharides include pentosans (composed of arabinose or xylose) from woods, nuts, and other plant products; and fructans (levans) composed of fructose, such as inulin from such roots and tubers as the Jerusalem artichoke and dahlia. Mannose homopolysaccharides occur in ivory nuts, orchid tubers, pine trees, fungi, and bacteria. Pectins (pectin), found in fruits and berries and used commercially as gelling agents, consist of a derivative of galacturonic acid (itself a derivative of the sugar galactose). The repeating unit of chitin, a component of the outer skeleton of arthropods (e.g., insects, crustaceans) is N-acetyl-d-glucosamine, a compound derived from glucose; shells of arthropods such as crabs and lobsters contain about 25 percent chitin. It is also found in certain structures of annelid worms, mollusks, and other invertebrate groups (e.g., jellyfishes, bryozoans, nematodes, and acanthocephalans). The cell walls of most fungi also are chitin. Chitin in nature is linked to protein.

      Polysaccharides consisting of molecules of more than one sugar or sugar derivative are called heteropolysaccharides (heteroglycans). Most contain only two different units and are associated with proteins (glycoproteins; e.g., gamma globulin from blood plasma, acid mucopolysaccharides) or lipids (glycolipids; e.g., gangliosides in the central nervous system). Acid mucopolysaccharides are widely distributed in animal tissues. The basic unit is a so-called mixed disaccharide consisting of glucuronic acid linked to N-acetyl-d-glucosamine. The most abundant mucopolysaccharide, hyaluronic acid from connective tissue, is also the major component of joint fluid (synovia) and occurs in the soft connective tissue (Wharton's jelly) of the umbilical cord of mammals. Glucuronic acid linked to N-acetyl-d-galactosamine is the repeating unit of chondroitin sulfate, a heteropolysaccharide found in cartilage. heparin, a heteropolysaccharide related to the acid mucopolysaccharides, has anticoagulant properties and is present in connective and other tissues.

      Complex heteropolysaccharides occur in plant gums such as gum arabic from Acacia and gum tragacanth from Astragalus. Most contain glucuronic acid and various sugars. Produced after either mechanical damage to bark (a method used in commercial production) or an attack on the bark by certain bacteria, insects, or fungi, plant gums are used in the arts (gum arabic) and as an adhesive agent and emulsifying agent (gum tragacanth). Heteropolysaccharides also occur in bacterial cell walls.

* * *


Universalium. 2010.

Look at other dictionaries:

  • Polysaccharide-K — Polysaccharide K, also known as PSK, is a proteoglycan found in the polypore fungus Trametes versicolor. The results obtained from a large number of published scientific studies and clinical trials show that PSK is a powerful immunomodulator… …   Wikipedia

  • polysaccharide — [ pɔlisakarid ] n. m. • 1884; de poly et saccharide ♦ Biochim. Glucide naturel, végétal ou animal, formé par la condensation de plusieurs sucres simples (oses). ⇒ polyoside. L amidon, la cellulose sont des polysaccharides. ● polysaccharide nom… …   Encyclopédie Universelle

  • polysaccharide — polysaccharide. См. гликан. (Источник: «Англо русский толковый словарь генетических терминов». Арефьев В.А., Лисовенко Л.А., Москва: Изд во ВНИРО, 1995 г.) …   Молекулярная биология и генетика. Толковый словарь.

  • Polysaccharide — Polysaccharide, s. Kohlehydrate, S. 232 …   Meyers Großes Konversations-Lexikon

  • Polysaccharide — Polysaccharide, spaltbare, nicht zuckerähnliche Kohlehydrate, wie die Dextrine, Stärke, Cellulose; s. Kohlehydrate …   Lexikon der gesamten Technik

  • Polysaccharide — Polysaccharide,   Glykane, hochpolymere Kohlenhydrate, in denen Monosaccharide oder ihre Derivate durch glykosidischen Bindungen miteinander verknüpft sind. Homopolysaccharide (Homoglykane) enthalten nur ein Monosaccharid als Baustein (z. B.… …   Universal-Lexikon

  • Polysaccharide — Polysaccharide, zu den Kohlenhydraten gehörende, durch α oder β glykosidische Verknüpfung von mehr als 10 gleichen (Homoglycane) oder verschiedenen (Heteroglycane) Monosaccharideinheiten entstehende, linear aufgebaute oder verzweigte… …   Deutsch wörterbuch der biologie

  • polysaccharide — [päl΄i sak′ə rīd΄] n. [ POLY + SACCHARIDE] any of a group of complex carbohydrates, as starch, that decompose by hydrolysis into a large number of monosaccharide units …   English World dictionary

  • Polysaccharide — Die Cellulose ist ein wichtiges Strukturelement der Pflanzen und das am häufigsten vorkommende Polysaccharid. Polysaccharide (auch als Mehrfachzucker, Vielfachzucker, Glycane/Glykane[1] oder Polyosen[2] bezeichnet) sind Koh …   Deutsch Wikipedia

  • Polysaccharide — Polysaccharides are relatively complex carbohydrates. They are polymers made up of many monosaccharides joined together by glycosidic bonds. They are therefore very large, often branched, macromolecules. They tend to be amorphous, insoluble in… …   Wikipedia

  • Polysaccharide — ██████████40  …   Wikipédia en Français


Share the article and excerpts

Direct link
Do a right-click on the link above
and select “Copy Link”

We are using cookies for the best presentation of our site. Continuing to use this site, you agree with this.