This is the main storage poly-saccharide in animals. Hence, it is commonly called animal starch. Like amylopectin, glycogen gives a red-violet colour when treated with iodine. While being used in cells for energy, it is broken down by hydrolysis into its glucose monomers (glycogenolysis), but only liver cells release this glucose into the blood for utilization by all body cells. Glycogen stored in muscle cells is utilized only by these cells themselves.