What Is a Polysaccharide?

Polysaccharides are carbohydrate molecules formed from long chains of monosaccharides. All polysaccharides contain glucose. Humans, animals and plants synthesize polysaccharides and store them for food or structural support, or metabolize them for energy. Some common examples include plant starch, glycogen and cellulose.

Polysaccharides may range from linear to highly complex in structure. There are two types of plant starches: amylose and amylopectin. Amylopectin is branched while amylose is not.

Amylose is a helical chain made of glucose monomers, bonded together by glycosidic linkages. Amylose can be found in plants such as potatoes and used as a primary energy source for humans. Amylopectin can also be used as a primary energy source for humans.

Glycogen is a storage polysaccharide found in animals. It is similar to amylopectin but is more highly branched, and its molecules are tighter. Glycogen can be used by humans as an energy source.

Cellulose has a beta acetal linkage which separates it from starch. It is a major component in plant cell walls. Humans lack the appropriate enzymes to break down beta acetal linkages and therefore cannot digest cellulose. In its undigested form, it is used in aiding the smooth working of the human intestinal tract. Cellulose can also be found in wood, paper, cotton and linen.