Polysaccharides are complex polymeric carbohydrate structures, formed by polymerization of monomeric repeating units (either mono-or di-saccharides) joined together by glycosidic bonds.
Example: starch, glycogen, etc. Polysaccharides are formed by enzyme catalyzed condensation reaction between any number of saccharide units.
Starch : It is the nutritional reservoir of plants. They are formed by the polymerisation/condensation of glucose molecules. Two types of starch are possible unbranched starch known as Amylase and branched starch known as Amylopectin. They actually differ in glycosidic linkage.
Glycogen : It is the storage form of glucose in animals. Two chains of glucose molecules joined by an alpha-1, 4-glycosidic bonds are linked by an alpha-1. 6-glycosidic bond to create a branch point.