Discuss the structural differences between the polysaccharides starch and glycogen, explaining how the differences in structure contribute to the functional properties of the molecule

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.