Animals and fungi store food reserves as glycogen or fat.
Glycogen is a branched biopolymer consisting of linear chains of glucose residues with an average chain length of approximately 8–12 glucose units and 2,000-60,000 residues per one molecule of glycogen. Glucose units are linked together linearly by α(1→4) glycosidic bonds from one glucose to the next.
In glycogen, the right end is called the reducing end and the left end is called the non-reducing end.