Glycogenolysis is defined as

Glycogenolysis is defined as

• A. The breakdown of glycogen into glucose to raise blood sugar levels.
• B. The production of glycogen from glucose.
• C. The breakdown of glucose into lactate.
• D. The process of glucose phosphorylation.

Answer: (A)

Glycogenolysis is the process of breaking down stored glycogen into glucose to raise blood glucose levels when energy is needed or during fasting. In the liver, glycogen phosphorylase cleaves the glycogen to release glucose-1-phosphate, which is converted to glucose-6-phosphate and then, via glucose-6-phosphatase, to free glucose that enters the bloodstream. In muscle, the same breakdown provides substrate for glycolysis to meet local energy needs, but glucose-6-phosphatase is absent, so free glucose isn’t released into blood. This sets glycogenolysis apart from glycogenesis, which is the synthesis of glycogen from glucose, and from glycolysis, which is the breakdown of glucose to pyruvate or lactate. Glucose phosphorylation refers to adding a phosphate to glucose, the first step of glycolysis, not the breakdown of glycogen.

Glycogenolysis is the process of breaking down stored glycogen into glucose to raise blood glucose levels when energy is needed or during fasting. In the liver, glycogen phosphorylase cleaves the glycogen to release glucose-1-phosphate, which is converted to glucose-6-phosphate and then, via glucose-6-phosphatase, to free glucose that enters the bloodstream. In muscle, the same breakdown provides substrate for glycolysis to meet local energy needs, but glucose-6-phosphatase is absent, so free glucose isn’t released into blood. This sets glycogenolysis apart from glycogenesis, which is the synthesis of glycogen from glucose, and from glycolysis, which is the breakdown of glucose to pyruvate or lactate. Glucose phosphorylation refers to adding a phosphate to glucose, the first step of glycolysis, not the breakdown of glycogen.