The function of liver glycogen is to maintain glucose homeostasis, generating glucose via glycogenolysis to compensate for the decrease of glucose levels that can occur between meals. Thanks to the presence of the glucose-6-phosphatase enzyme, the hepatocytes are capable of turning glycogen to glucose, releasing it into blood to prevent hypoglycemia. 
In skeletal muscle, glycogen is used as an energy source for muscle contraction during exercise. The different functions of glycogen in muscle or liver make the regulation mechanisms of its metabolism differ in each tissue. These mechanisms are based mainly on the differences on structure and on the regulation of the enzymes that catalyze synthesis, glycogen synthase (GS), and degradation, glycogen phosphorylase (GF).