Glycogen is the main storage polysaccharide in animals. Hence, it is commonly called animal starch. Blue-green algae and fungi also store glycogen as fuel reserve. Like those of amylopectin, glycogen molecules-.are also arge and highly branched (branch points are α1−6 linkages) polymers of thousands of D-glucose residues linked by a, α,1−4 glycosidic bonds. In comparison to amylopectin molecules, however, glycogen molecules are much larger, more extensively branched and more compactly coiled concentrically. Vertebrate animals store glycogen in liver and skeletal muscles. Stored glycogen mayrespectively account for upto 10% and 2% of liver and muscles by weight in man and other animals. Thus, a total of about 400 gm of glycogen (about 100 gm in liver and about 300 gm in skeletal muscles) is normally found in body of an average adult human being. In liver cells, the glycogen is found in large, flattened and ellipsoidal grains. Each grain is a cluster of small granules and each granule is a single, compact glycogen molecule. Sucrose and lactose are disaccharides of D-glucose and D-fructose and D-glucose and D galactose respectively. Fructose is a monosaccharide.