👉 Glycogen, also known as glycogenolysis, is a metabolic process in which glucose molecules are broken down into smaller units called glycogen molecules. This process occurs during periods of energy storage or breakdown in the body. It can be thought of as the conversion of glucose molecules to simpler forms that can be used by cells for energy production. Glycogen stores in the liver, muscle, and some fat cells throughout the body. When a person exercises, for example, it releases