Glycogen is a complex carbohydrate and the primary storage form of glucose in animals and humans. It serves as an energy reserve, allowing organisms to store glucose for later use when the body's energy demands increase. Glycogen is mainly stored in the liver and muscles.

The structure of glycogen resembles a highly branched tree, consisting of many glucose molecules linked together. It is synthesized through a process called glycogenesis, which involves the activation of an enzyme called glycogen synthase. When blood glucose levels are high, excess glucose is converted into glycogen and stored in the liver. Later, when blood glucose levels drop, glycogen is broken down into glucose through a process called glycogenolysis. This provides a quick and readily available source of glucose for energy production.

Glycogen plays a crucial role in maintaining blood sugar levels during fasting periods or intense physical activity. It acts as a buffer, preventing sudden drops in blood glucose levels, which can lead to hypoglycemia.

In addition to its role in energy storage, glycogen also has structural functions. It helps maintain the structure and integrity of cells, particularly in tissues like the liver and muscles.

Overall, glycogen is an important energy reserve and plays a vital role in regulating blood glucose levels and supporting various physiological processes in the body.

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