Cellulose
(C6H10O5)n
is a long-chain polymer polysaccharide carbohydrate, of beta-glucose. It forms the primary structural component of plants and is not digestible by humans.
History and Applications
Cellulose is a common material in plant cell walls and was first noted as such in 1838. It occurs naturally in almost pure form only in cotton fibre; in combination with lignin and any hemicellulose, it is found in all plant material. Cellulose is the most abundant form of living terrestrial biomass (Crawford, R. L. 1981. Lignin biodegradation and transformation, John Wiley and Sons, New York.) Cellulose, especially cotton linters , is used in the manufacture of nitrocellulose, historically used in smokeless gunpowder.
Some animals, particularly ruminants and termites, can digest cellulose with the help of symbiotic micro-organisms - see methanogen.
Cellulose is processed to make cellophane and rayon, and more recently Modal, a textile derived from beechwood cellulose.
Cellulose is also used within the laboratory as a solid-state substrate for thin layer chromotography.
Chemistry
Cellulose monomers (beta-glucose) are linked together through 1,4 glycosidic bonds. Cellulose is a straight chain (no coiling occurs). In microfibrils, the multiple hydroxide groups hydrogen bond with each other, holding the chains firmly together and contributing to their high tensile strength. This strength is important in cell walls, where they are meshed into a carbohydrate matrix, helping keep plants rigid.
Given a cellulose material, the portion that does not dissolve in a 17.5% solution of sodium hydroxide at 20 deg C. is Alpha Cellulose, which is true cellulose; the portion that dissolves and then precipitates upon acidification is Beta Cellulose, and the proportion that dissolves but does not precipitate is Gamma Cellulose.
See also