Final answer:
Glycogen is the storage form of glucose in animals, found predominantly in liver and skeletal muscle cells. It is vital for maintaining blood glucose levels and providing energy during physical activity. The body predominantly stores glycogen in skeletal muscle due to its greater mass, but liver glycogen is more dense by weight.
Step-by-step explanation:
The storage form of glucose in humans and other vertebrates is known as glycogen. This substance is a polymer of glucose, meaning it is a large molecule made up of many glucose units linked together. Glycogen functions as an energy reserve in the body, akin to starch in plants.
Significant amounts of glycogen are located in liver and skeletal muscle cells. In the liver, glycogen can make up about 4%-8% of the tissue by weight. It is critical for maintaining blood glucose levels, as it provides glucose to other cells when necessary. Muscle glycogen, constituting about 0.5%-1.0% by weight of tissue, primarily serves as a local energy source that can be rapidly mobilized during vigorous exercise.
Approximately 70% of the body's total glycogen is stored within muscle cells. However, the liver's glycogen is denser by weight. Despite this, the overall mass of the skeletal muscle in the body allows it to store a greater absolute amount of glycogen compared to the liver. When blood glucose levels fall, a process called glycogenolysis occurs, where glycogen is broken down to release glucose to maintain energy supply.