Glycogen is predominantly stored in which tissues?

• A. Liver and Skeletal muscle
• B. Brain
• C. Adipose tissue
• D. Heart

Answer: (A)

Glycogen stores serve two main purposes in different tissues. The liver holds a large reservoir to keep blood glucose stable between meals and during fasting; hepatocytes can release glucose into the bloodstream because they express glucose-6-phosphatase, which liberates free glucose from glycogen-derived glucose-6-phosphate. Skeletal muscle, by contrast, stores glycogen to power its own contractions during exercise, but cannot export glucose because muscle tissue lacks glucose-6-phosphatase, so the glucose-6-phosphate stays local for glycolysis. Other tissues—like brain, adipose tissue, and heart—have only small glycogen stores or rely more on other energy sources. Thus glycogen is predominantly stored in the liver and skeletal muscle.