Polysaccharides - Introduction

Polysaccharides: They consist of repeat units of monosaccharides or their derivatives. These units are held by glycosidic bonds. These carbohydrates liberate large number of monosaccharide molecules on hydrolysis. They are colorless and tasteless. So, they are called non-sugars. They are concerned with two important functions - structural and storage of energy. Some examples of polysaccharides are starch, cellulose, glycogen and dextrins. However starch and cellulose are the most important of these. Polysaccharides are linear as well as branched polymers. The general formula is (C6H10O5)n, where 'n' stands for a very large number. The occurrence of branches in polysaccharides is due to the glycosidic linkages formed at any one of the hydroxyl groups of a monosaccharide.

POLYSACCHARIDES are condensation polymers of simpler units called MONOSACCHARIDES, which belong to a very large group of organic molecules called CARBOHYDRATES, that is, molecules that contain only carbon, hydrogen and oxygen . A simple monosaccharide, glucose, has the structure shown here on the left. Amylose is a glucose polymer with a(1®4) glycosidic linkages, as represented above (see also diagram p. 366). The end of the polysaccharide with an anomeric carbon (C1) that is not involved in a glycosidic bond is called the reducing end.