Stores of readily available glucose to supply the tissues with an oxidizable energy source are found principally in the liver, as glycogen. Glycogen is a polymer of glucose residues linked by α-(1,4)- and α-(1,6)-glycosidic bonds.A second major source of stored glucose is the glycogen of skeletal muscle. However, muscle glycogen is not generally available to other tissues, because muscle lacks the enzyme glucose-6-phosphatase.Glycogen Structure.tores of readily available glucose to supply the tissues with an oxidizable energy source are found principally in the liver, as glycogen. Glycogen is a polymer of glucose residues linked by α-(1,4)- and α-(1,6)-glycosidic bonds.