Which type of polysaccharide is primarily used for energy storage in animals?

Glycogen is the primary polysaccharide used for energy storage in animals. It is a highly branched molecule composed of glucose units, making it an efficient form for quick energy release. Glycogen is predominantly stored in the liver and muscle tissues. When the body requires glucose, such as during exercise or between meals, glycogen can be rapidly broken down into glucose monomers and released into the bloodstream to maintain blood sugar levels or provide immediate energy for muscle activity.

In contrast, cellulose is a structural polysaccharide found in plant cell walls, which humans and many animals cannot digest due to the lack of necessary enzymes. Chitin, while also a structural polysaccharide, is found in the exoskeletons of arthropods and fungal cell walls, serving a different function altogether. Amylopectin is one of the two components of starch, found primarily in plants for energy storage, but it is not the primary storage polymer in animals. Thus, glycogen is uniquely suited for the energy storage needs of animal physiology.