Glycogen is a homopolysaccharide formed by units of glucose and is sometimes referred to as animal starch. It can reach up to a molecular weight of 10 to the power 8 DA which corresponds to about 600,000 glucose molecules.
The function of glycogen is that it is the principal form in which glucose is stored in animals and is present in the liver, muscle (skeletal and heart muscle) and in lower amounts in nearly all the other tissues and organs.
Glycogen makes up about 10% of liver weight and 1% of muscle weight. Although it is present in higher a concentration in the liver, the total amount stored in muscles is much higher due the greater mass of the muscles as compared to the liver.