Polysaccharides, such as starch and glycogen, are complex chains of carbohydrates composed of monosaccharide units, such as glucose. Plants and animals store excess energy for later use or as structural support. Animals create starch ito store unused energy for later, while animals store glycogen for the same purpose. Both starch and glycogen break down into monosaccharides.
When animals covert glucose into glycogen, the glycogen is primarily stored in the liver and muscle. Not only is glycogen stored in the liver, it is mainly produced by the liver. The process of converting glucose into glycogen is called glycogenesis. When the body needs glucose because its blood glucose level has become too low, the body releases glucagon (a hormone) to begin the process of glycogenolysis, which is the breakdown of stored glycogen into glucose.
Starch is produced in plants through photosynthesis, a process that requires light. Because of variations in weather, the storage of starch in plants is very important to ensure energy throughout the year. Plants break down starch for use through a process called hydrolysis, which is the same process animals use to break down starch. One of the forms of starch is insoluble (unable to be dissolved in water) and the other is soluble.
Glycogen and Starch Structure
The structures of glycogen and starch have similarities and differences. Starch has two structures, amylose and amylopectin. The amylose structure is distinct to starches and is not found in glycogen. The amylopectin structure is found in both glycogen and starch. This form of the polysaccharides has alpha 1-4 glycosidic bonds and alpha 1-6 glycosidic bonds, according to the City University of New York, Brooklyn College. The amylopectin structure in glycogen includes additional glucose molecules.
Starch in Animals
Starch is in many of the foods that humans and animals eat, such as wheat, rice, corn, oats and barley. When an animal consumes starch, it is broken down into various monosaccharides (simple sugars such as glucose). If an animal does not immediately use the broken-down starch (or glucose), it is converted from glucose to glycogen for storage. Humans cannot store starch as starch.