Starch, cellulose and glycogen are all polymers of glucose. But they differ in function as optical isomerism is involved here.
starch is a mixture of two polysaccharides: amylose and amylopectin. The alpha-1,4 glycosidic bonds and branching is responsible for its physical properties. Starch can be easily hydrolyzed and is powdery than cellulose, which exists as tough microfibrils.
Glycogen, is a branched polymer, like starch . It is similar to amylopectin, being composed of alpha-glucose molecules, but it is larger and there are more alpha-1,6 links. This makes it highly branched, more soluble, and more easily hydrolized than starch.
Cellulose is an long chain, unbranched, glucose polymer held by beta-1,4 glycosidic bonds. The straight, tightly packed chains give cellulose high tensile strength and resistance to hydrolysis.
