Glycogenolysis breaks down glycogen to release which molecule?

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

Answer: (A)

Glycogenolysis mainly yields glucose-1-phosphate. The enzyme glycogen phosphorylase cleaves the α-1,4 glycosidic bonds at the ends of glycogen, releasing glucose units in the form of glucose-1-phosphate. A secondary debranching step can release some free glucose, but the primary immediate product is glucose-1-phosphate. This glucose-1-phosphate is then converted to glucose-6-phosphate by phosphoglucomutase, and in the liver, glucose-6-phosphatase can remove the phosphate to release free glucose for circulation. In muscle, the glucose-6-phosphate typically enters glycolysis for energy, and pyruvate is produced later in that pathway.