Here's why:

* Polysaccharides are complex carbohydrates made up of long chains of monosaccharides (simple sugars) linked together.

* Cellulose is a polysaccharide made up of long chains of glucose molecules linked together in a linear fashion. It is the primary structural component of plant cell walls.

* Glycogen is a polysaccharide made up of highly branched chains of glucose molecules. It serves as the primary energy storage form in animals.

While both are polysaccharides, they differ in their structure and function. Cellulose is a structural component, while glycogen is an energy storage molecule.