Final answer:
Starch, composed of amylose and amylopectin, is for energy storage in plants. Glycogen, with a high branch density, serves as the main form of carbohydrate energy storage in animals. Cellulose provides structural support in plant cell walls.
Step-by-step explanation:
The phrases describe the polysaccharides starch, glycogen, and cellulose, which are essential carbohydrates with different roles in living organisms. Starch is made up of two glucose polysaccharides: amylose and amylopectin, and provides energy storage in plants. Glycogen is the main energy storage form of carbohydrates in animals, particularly stored in the liver and muscle cells. Cellulose provides structural support for plants and is a significant component of cell walls. Both starch and cellulose are plant polysaccharides, with starch being easily digested by humans, while cellulose is not because of the different linkages in its glucose units.