Final answer:
Glycogen is a branched polysaccharide made of glucose monomers, serving as an energy reserve in liver and muscle cells. It is crucial for maintaining glucose levels in the blood, and releasing glucose when needed.
Step-by-step explanation:
Glycogen is the main storage form of glucose in humans and other vertebrates, composed of glucose monomers. It serves as an animal equivalent to starch and represents a highly branched polysaccharide. Primarily found in liver and muscle cells, glycogen plays a critical role in energy storage and maintaining blood glucose levels during fasting or between meals. When blood glucose levels decrease, glycogen undergoes glycogenolysis, where it is broken down to release glucose.
This process ensures a consistent energy supply and is vital for activities such as exercise and metabolic functions. Notably, glycogen is stored with much less water compared to glucose, making it an efficient source of energy. The presence of glycogen allows for sustained ATP production during prolonged periods, such as exercise, and is essential for the homeostasis of blood glucose levels.