Hemicellulose


Hemicellulose

A hemicellulose can be any of several heteropolymers (matrix polysaccharides) present in almost all plant cell walls along with cellulose. While cellulose is crystalline, strong, and resistant to hydrolysis, hemicellulose has a random, amorphous structure with little strength. It is easily hydrolyzed by dilute acid or base as well as myriad hemicellulase enzymes.

Composition

Hemicellulose contains many different sugar monomers. In contrast, cellulose contains only anhydrous glucose. For instance, besides glucose, sugar monomers in hemicellulose can include xylose, mannose, galactose, rhamnose, and arabinose. Hemicelluloses contain most of the D-pentose sugars, and occasionally small amounts of L-sugars as well. Xylose is always the sugar monomer present in the largest amount, but mannuronic acid and galacturonic acid also tend to be present.

tructural comparison to cellulose

Unlike cellulose, hemicellulose (also a polysaccharide) consists of shorter chains - 500-3000 sugar units as opposed to 7,000 - 15,000 glucose molecules per polymer seen in cellulose. In addition, hemicellulose is a branched polymer, while cellulose is unbranched.

Native structure

Hemicelluloses are embedded in the cell walls of plants, sometimes in chains that form a 'ground' - they bind with pectin to cellulose to form a network of cross-linked fibres.

Applications

As percent content of hemicellulose increases in animal feed the voluntary feed intake decreases.

Hemicelluloses include xylan, glucuronoxylan, arabinoxylan, glucomannan, and xyloglucan.

Hemicellulose is represented by the difference between neutral detergent fiber (NDF) and acid detergent fiber (ADF).

See also

* Cellulose
* Lignin


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  • hémicellulose — [ emiselyloz ] n. f. • 1893; de hémi et cellulose ♦ Biochim. Association de polysaccharides de haut poids moléculaire, coexistant avec la cellulose dans les parties ligneuses des végétaux, et soluble dans les solutions alcalines. ● hémicellulose… …   Encyclopédie Universelle

  • hemicellulose — [hem΄i sel′yə lōs΄] n. a polysaccharide with less than 150 polymer units of various sugars, that is extracted from plants, esp. woody and corn fiber, by dilute alkalies …   English World dictionary

  • Hemicellulose — Aufbau einer nicht verholzten pflanzlichen Zellwand: Hemicellulose grün Hemicellulose ist ein Sammelbegriff für in pflanzlicher Biomasse vorkommende Gemische von Polysacchariden (Vielfachzuckern) in veränderlicher Zusammensetzung. Die am… …   Deutsch Wikipedia

  • Hémicellulose — L hémicellulose est une des composantes du bois. C est le deuxième composant d une paroi pectocellulosique chez les végétaux, après la cellulose. Elle a un rôle de pontage entre les fibres de cellulose, mais aussi avec d autres composés… …   Wikipédia en Français

  • hemicellulose — hemiceliuliozė statusas T sritis chemija apibrėžtis Šarmuose tirpstantis augalų polisacharidas. atitikmenys: angl. hemicellulose; pseudocellulose rus. гемицеллюлоза …   Chemijos terminų aiškinamasis žodynas

  • hemicellulose — noun Etymology: International Scientific Vocabulary Date: 1891 any of various plant polysaccharides less complex than cellulose and easily hydrolyzable to monosaccharides and other products …   New Collegiate Dictionary

  • hemicellulose — Class of plant cell wall polysaccharide that cannot be extracted from the wall by hot water or chelating agents, but can be extracted by aqueous alkali. Includes xylan, glucuronoxylan, arabinoxylan, arabinogalactan II, glucomannan, xyloglucan,… …   Dictionary of molecular biology

  • hemicellulose — /hem i sel yeuh lohs /, n. any of a group of gummy polysaccharides, intermediate in complexity between sugar and cellulose, that hydrolyze to monosaccharides more readily than cellulose. [1890 95; HEMI + CELLULOSE] * * * ▪ chemical compound… …   Universalium

  • hemicellulose — noun a mixture of several plant polysaccharides, of smaller molecular weight than cellulose, that are soluble in dilute alkali; they are involved in the manufacture of paper, and are used in the production of furfural and ethanol …   Wiktionary