Cellulose, starch, and glycogen are all polymers of glucose, but differ in form and function because of the optical isomer involved, the length of the polymers, and the degree of branching.
CELLULOSE is an unbranched, long chain glucose polymer held by ß-1,4 glycosidic bonds. The straight, tightly packed chains give cellulose high tensile strength and resistance to hydrolysis.
STARCH is a mixture of two polysaccharides: amylose (unbranched with alpha-1,4 glycosidic bonds) and amylopectin (branched with alpha-1,6 glycosidic bonds). The alpha-1,4 glycosidic bonds and more branched nature of starch account for ith physical properties; starch is powdery and more easily hydrolyzed than cellulose, which exists as tough microfibrils.
GLYCOGEN, like starch, is a branched polymer. 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.
