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Hemicellulose
 
 
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A hemicellulose can be any of several heteropolymer
Heteropolymer

A heteropolymer or copolymer is a polymer derived from two monomeric species, as opposed to a homopolymer where only one monomer is used....
s (matrix polysaccharides) present in almost all plant cell walls along with cellulose
Cellulose

File:Cellulose Sessel.svgCellulose is an organic compound with the chemical formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand ? linked D-glucose units....
. While cellulose is crystalline, strong, and resistant to hydrolysis
Hydrolysis

Hydrolysis is a chemical reaction during which one or more water are split into hydrogen and hydroxide ions which may go on to participate in further reactions....
, hemicellulose has a random, amorphous structure with little strength. It is easily hydrolyzed by dilute acid or base as well as myriad hemicellulase enzymes.

cellulose contains many different sugar monomers.






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A hemicellulose can be any of several heteropolymer
Heteropolymer

A heteropolymer or copolymer is a polymer derived from two monomeric species, as opposed to a homopolymer where only one monomer is used....
s (matrix polysaccharides) present in almost all plant cell walls along with cellulose
Cellulose

File:Cellulose Sessel.svgCellulose is an organic compound with the chemical formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand ? linked D-glucose units....
. While cellulose is crystalline, strong, and resistant to hydrolysis
Hydrolysis

Hydrolysis is a chemical reaction during which one or more water are split into hydrogen and hydroxide ions which may go on to participate in further reactions....
, 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
Xylose

Xylose, or wood sugar, is an aldopentose — a monosaccharide containing five carbon atoms and including an aldehyde functional group. It has chemical formula 5105....
, mannose
Mannose

Mannose is a sugar monomer of the hexose series of carbohydrates....
, galactose
Galactose

Galactose is a type of Carbohydrate which is less sweetness than glucose. It is considered a nutritive sweetener because it has food energy.Galactan is a polymer of the sugar galactose....
, rhamnose
Rhamnose

Rhamnose is a naturally-occurring deoxy sugar. It can be classified as either a methyl-pentose or a 6-deoxy-hexose. Rhamnose occurs in nature in its levorotary-form as L-rhamnose ....
, and arabinose
Arabinose

Arabinose is an aldopentose — a monosaccharide containing five carbon atoms, and including an aldehyde functional group. It has chemical formula Carbon5Hydrogen10Oxygen5 and a molar mass of 150.13 g/mol....
. Hemicelluloses contain most of the D-pentose
Pentose

A pentose is a monosaccharide with five carbon atoms.They either have an aldehyde functional group in position 1 , or a ketone functional group in position 2 ....
 sugars, and occasionally small amounts of L-sugars as well. Xylose
Xylose

Xylose, or wood sugar, is an aldopentose — a monosaccharide containing five carbon atoms and including an aldehyde functional group. It has chemical formula 5105....
 is always the sugar monomer present in the largest amount, but mannuronic acid
Mannose

Mannose is a sugar monomer of the hexose series of carbohydrates....
 and galacturonic acid also tend to be present.

Structural 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
Matrix (biology)

In biology, matrix is the material between animal or plant cell , the material in which more specialized structures are embedded, and a specific part of the mitochondrion that is the site of oxidation of organic molecules....
' - they bind with pectin
Pectin

Pectin is a structural heteropolysaccharide contained in the primary cell walls of terrestrial plants. It was first isolated and described in 1825 by Henri Braconnot....
 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
Xylan

Xylan is a generic term used to describe a wide variety of highly complex polysaccharides that are found in plant cell walls and some algae.It is found in almost all parts of the plant....
, glucuronoxylan, arabinoxylan, glucomannan
Glucomannan

Glucomannan is a water-soluble polysaccharide that is considered a dietary fiber. Glucomannan is a food additive used as an emulsifier and thickener....
, and xyloglucan
Xyloglucan

Xyloglucan is the most abundant hemicellulose in the primary cell wall of many dicotyledonous plants, and occurs in the primary cell walls of all vascular plants....
.

Hemicellulose is represented by the difference between neutral detergent fiber
Neutral Detergent Fiber

Neutral Detergent Fiber is the most common measure of fiber used for animal feed analysis, but it does not represent a unique class of chemical compounds....
 (NDF) and acid detergent fiber (ADF).

Functions

Microfibrils are cross-linked together by Hemicellulose homopolymers. Lignins assist and strengthen the attachment of Hemicelluloses to microfibrils.

See also

  • Cellulose
    Cellulose

    File:Cellulose Sessel.svgCellulose is an organic compound with the chemical formula , a polysaccharide consisting of a linear chain of several hundred to over ten thousand ? linked D-glucose units....
  • Lignin
    Lignin

    Lignin or lignen is a complex chemical compound most commonly derived from wood, and an integral part of the secondary cell walls of plants and some algae....
  • Pectin
    Pectin

    Pectin is a structural heteropolysaccharide contained in the primary cell walls of terrestrial plants. It was first isolated and described in 1825 by Henri Braconnot....