Glycogen is structurally similar to amylopectin. Both glycogen and amylopectin are polysaccharides that serve as energy storage in organisms. They are made up of glucose units linked together in a branched structure, which allows for quick mobilization of glucose when energy is needed.
Amylopectin is a component of starch and has a similar branched structure, consisting of α(1→4) linked glucose units with α(1→6) branches. Glycogen, found in animals, has even more frequent branching, making it more readily available for energy release. In contrast, amylose, another component of starch, is a linear chain of glucose units and cellulose consists of β(1→4) linked glucose units, which is used for structural purposes in plants. Thus, the correct answer is a) amylopectin.