Glycogen is primarily stored in which organ's cells?

• A. Liver
• B. Heart
• C. Kidney
• D. Spleen

Answer: (A)

Glycogen storage primarily serves the body's need to regulate blood glucose. The liver functions as the main glycogen reservoir because hepatocytes store glycogen to release glucose into the bloodstream between meals, helping keep blood sugar levels stable. This capacity relies on glucose-6-phosphatase in the liver, which converts glucose-6-phosphate to free glucose that can exit the cell and enter circulation.

In contrast, skeletal muscle also stores glycogen, but its purpose is to supply energy locally for muscle contraction during activity. Muscle tissue lacks glucose-6-phosphatase, so it cannot release free glucose into the blood for systemic use. Other organs like the heart, kidney, or spleen may contain some glycogen, but their stores are small and do not play a major role in maintaining blood glucose.