The most useful carbohydrate classification scheme divides the carbohydrates into groups according to the number of individual simple sugar units. Monosaccharides contain a single unit; disaccharides contain two sugar units; and polysaccharides contain many sugar units as in polymers - most contain glucose as the monosaccharide unit.
Thumbnail: Schematic two-dimensional cross-sectional view of glycogen: A core protein of glycogenin is surrounded by branches of glucose units. The entire globular granule may contain around 30,000 glucose units. By Mikael Häggström, used with permission (Public Domain).