What process involves the breakdown of glycogen into glucose-6-phosphate?

The breakdown of glycogen into glucose-6-phosphate is known as glycogenolysis. This process occurs primarily in the liver and muscles, where glycogen is stored as a readily accessible form of energy. During glycogenolysis, enzymes, such as glycogen phosphorylase, cleave the glycosidic bonds in glycogen, progressively releasing glucose units. The glucose released from glycogen is then phosphorylated to form glucose-6-phosphate, which can enter the glycolytic pathway or, in the case of the liver, can be dephosphorylated to yield free glucose for release into the bloodstream.

Understanding glycogenolysis is crucial, as it highlights the body's ability to mobilize energy reserves in response to hormonal signals, such as those from glucagon or epinephrine, when blood glucose levels drop or during times of increased energy demand. This mechanism contrasts sharply with glycogenesis, which is the process of synthesizing glycogen from glucose, and other pathways like glycolysis and gluconeogenesis, which deal with the metabolism of glucose, rather than its storage and breakdown.