During glycogenolysis, what is the immediate product produced from glycogen?

• A. Glucose-1-phosphate
• B. Glucose-6-phosphate
• C. Pyruvate
• D. Acetyl-CoA

Answer: (A)

Glycogenolysis begins with glycogen phosphorylase cleaving glucose units from the glycogen chain by phosphorolysis, using inorganic phosphate. This process yields glucose-1-phosphate as the immediate product. The glucose unit is kept phosphorylated, which allows rapid entry into metabolism: phosphoglucomutase then converts glucose-1-phosphate to glucose-6-phosphate, which can go into glycolysis in most tissues, or, in the liver, be dephosphorylated to free glucose for release into the blood. Pyruvate and acetyl-CoA appear later in metabolism after glycolysis and further steps, not as direct products of this initial glycogen breakdown. A small amount of free glucose can be released at branch points during debranching, but the primary immediate product from the main glycogen chain is glucose-1-phosphate.