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Polysaccharide

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Definition

noun, plural: polysaccharides

Any of a class of carbohydrates formed by repeating units linked together by glycosidic bonds


Supplement

A polymer produced by a living organism is called a biopolymer. There are three major classes of biopolymers: (1) polysaccharides, (2) polypeptides, and (3) polynucleotides. Polysaccharides are complex carbohydrates composed of a chain of monosaccharides joined together by glycosidic bonds.

Polysaccharides are characterized by the following chemical properties: (1) not sweet in taste, (2) insoluble in water, (3) do not form crystals when desiccated, (4) compact and not osmotically active inside the cells, (5) can be extracted to form white powder, and (6) general chemical formula of Cx(H2O) y. Examples of polysaccharides are cellulose, starch, and glycogen. Cellulose is a polysaccharide consisting of a linear chain of β (1→4) linked D-glucose units: (C6H10O5) n. Starch is a polysaccharide carbohydrate (C6H10O5)n consisting of a large number of glucose monosaccharide units joined together by glycosidic bonds found especially in seeds, bulbs, and tubers. Glycogen is a branched polymer of glucose that is mainly produced in liver and muscle cells, and functions as secondary long-term energy storage in animal cells.

Polysaccharides may be a homopolysaccharide or a heteropolysaccharide depending on their monosaccharide components. A homopolysaccharide (also called homoglycan) consists of same types of monosaccharides whereas a heteropolysaccharide (also called heteroglycan) is composed of different types of monosaccharides.


Word origin: poly ("many") + saccharide ("sugar")

Synonym(s):

  • glycan

See also:

Related term(s):