Which organ stores glycogen and is used to convert back to glucose during fasting?

• A. Liver
• B. Brain
• C. Heart
• D. Lungs

Answer: (A)

Maintaining blood glucose during fasting relies on breaking down stored glycogen in the liver and releasing glucose into the bloodstream. The liver stores glycogen and has the enzymes needed to convert it back into free glucose that can travel in the blood to fuel tissues like the brain. In contrast, skeletal muscle also stores glycogen but uses it mainly for its own energy needs and cannot export glucose to the blood. The brain uses glucose but does not store glycogen, and the heart and lungs do not serve as primary glycogen reservoirs for maintaining blood sugar. So, the organ that stores glycogen and can convert it back to glucose during fasting is the liver.