Glycogen is a multi-branched polysaccharide of glucose that serves as a form of energy storage in humans, animals, fungi, and bacteria. The ploysaccharide structure represents the main storage form of glucose in the body. In humans, the glycogen is made and stored primarily in the cells of the liver and skeletal muscle. Glycogen's role in maintaining blood-glucose levels is especially important because glucose is virtually the only fuel used by the brain, except during prolonged starvation. Moreover, the glucose in glycogen is reading mobilized and is therefore a good source of energy for sudden, strenuous activity.
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