Glycogen is the form in which animals store carbohydrates. Glycogen is a heavily branched polymer of alpha-glucose molecules, pictured on the right, covalently linked at carbon 1 of one molecule to carbon 6 or 4 of the next molecule. The arrows indicate the sites at which the molecule can link to other glucose molecules.
The heavy branching of glycogen is shown on the right. Heavy branching allows for quick breakdown of the molecule by enzymes to release glucose.