Glycogen

Glycogen is the carbohydrate reserve that animals store, functionally the direct animal-kingdom counterpart of plant starch. Structurally, glycogen closely resembles amylopectin (section 14.2.10a) -- built from alpha-D-glucose units joined by alpha-1,4-glycosidic linkages within each chain segment, with alpha-1,6-glycosidic linkages forming branch points -- but glycogen is considerably MORE highly branched than amylopectin, with branch points occurring much more frequently along the molecule. This denser branching gives glycogen a more compact, globular overall shape than amylopectin, and also means glycogen has many more 'free ends' available at any one time from which glucose units can be rapidly added (when the body is storing excess glucose) or rapidly removed (when the body needs a quick release of glucose for energy) -- a structural feature well suited to glycogen's biolog …