Polysaccharides - Polysaccharides are much larger, formed by the linkage of hundreds of monosaccharide
unit. Polysaccharides are classified as homopolysaccharides and heteropolysaccharides. omopolysaccharides are composed of normal monosaccharide molecules of a single type. Heteropolysaccharides are composed of modified monosaccharide molecules of different type.
Food storage polysaccharides: Those polysaccharides which are used as reserve food materials. At the time
of need food storage polysaccharides are hydrolyzed and the sugars are released which become readily
available to the living cells for the production of energy and biosynthetic activities.
Starch: It is a complex homopolysaccharide being formed of alpha glycoside chain and yields only glucose on
hydrolysis. It is formed by the condensation of amylose and amylopectin.
Glycogen: It Is also a complex homopolysaccharide and is the main carbohydrate storage material in animals
especially in mammals and fungi. It is formed of molecules amylopectin but with more numerous side chains. It
is a nonreducing substance and gives red colour with iodine.
Structural polysaccharide: It takes part in the formation of structural frame work of the cell wall and skeleton
of animals. The important structural polysaccharides are cellulose, chitin and lignin.
Cellulose: It is a homopolysaccharide which is found in the call wall of plants and in the external coverings of
all grains. It contains long chains of beta glycosides and may contain thousands of monosaccharide units in a
single molecule. Cellulose is absolutely insoluble in water and resistant to the action of dilute acids and
Chitin is an extracellular structural polysaccharide found in the cell walls of fungal hyphae and the
exoskeleton of arthropods. It is insoluble in water.