Glycogen is a major storage polysaccharide composed of glucose units, serving as the primary form of energy reserve in many biological systems. Structurally, it is a highly branched polymer, allowing for rapid mobilization of glucose molecules when energy demands increase. In animals, the synthesis and degradation of glycogen are critical for maintaining glucose homeostasis, with significant stores found predominantly in the liver and skeletal muscles. This complex metabolic pathway ensures a readily available supply of energy, supporting both basal metabolic functions and intense physical activity.