OCR General Certificate of Secondary Education (GCSE) Biology Practice Exam

What is glycogen?

1. A form of fat stored in the body

2. A simple sugar used for immediate energy

3. A storage form of glucose

4. A protein used for muscle recovery

The correct answer is: A storage form of glucose

Glycogen is a storage form of glucose found primarily in the liver and muscle tissues of animals. It serves as a readily accessible reserve of energy that the body can draw upon when needed, particularly during periods of increased physical activity or energy demand. When the body requires glucose for energy, glycogen can be rapidly broken down into glucose molecules through a process called glycogenolysis. This ability to store glucose as glycogen is crucial for maintaining blood sugar levels and providing a quick source of energy. The other choices do not accurately describe glycogen. While the body does store fat, glycogen is specifically a carbohydrate, not a form of fat. Simple sugars, such as glucose, are immediate sources of energy, but glycogen itself is a complex carbohydrate meant for storage rather than for immediate use. Lastly, glycogen is not a protein, and while proteins play important roles in muscle recovery, glycogen's primary function is to store glucose for energy rather than to serve as a recovery aid for muscle repair.