Advanced Placement (AP) Biology Practice Exam

Where is glycogen primarily stored in animals?

1. In the skin and hair

2. In the liver and muscle

3. In the brain and heart

4. In the lungs and kidneys

The correct answer is: In the liver and muscle

Glycogen is primarily stored in the liver and muscle tissues of animals, making this the correct response. The liver functions as a central depot for glycogen, releasing glucose into the bloodstream as needed to maintain blood sugar levels, especially in times of fasting or increased energy demand. Muscle tissue also stores glycogen, which serves as a readily available source of energy during physical activity. Muscle glycogen is specifically utilized locally by the muscle cells during exercise, allowing for quick access to glucose for ATP production. Other options mention storage in unrelated tissues, which do not serve as primary sites for glycogen storage. For example, skin and hair have no role in glycogen storage, while the brain and heart primarily rely on glucose and other substrates for energy but do not store significant quantities of glycogen. The lungs and kidneys are similarly not involved in glycogen storage, instead performing functions related to respiration and waste filtration, respectively. Understanding the specific roles of glycogen storage in the liver and muscles underscores the significance of these organs in energy metabolism and regulation in animals.