Which statement correctly distinguishes starch from cellulose?

• A. Starch provides structure to plant cell walls
• B. Cellulose stores energy in plants
• C. Glycogen stores energy in animals
• D. Starch stores energy in plants

Answer: (D)

Starch is the plant’s stored energy carbohydrate. Plants synthesize starch to stockpile glucose in a compact, insoluble form inside plastids, using two components (amylose and amylopectin) that can be broken back down to glucose when energy is needed. Cellulose, in contrast, is the structural backbone of plant cell walls. It’s built from glucose units linked by beta-1,4 glycosidic bonds, which creates rigid, linear chains that bundle into microfibrils to give plants their shape and rigidity—not to store energy. So stating that starch stores energy in plants captures the essential difference from cellulose. The other statements misassign roles: cellulose isn’t a storage material, and starch isn’t the structural component for cell walls (that’s cellulose). Glycogen stores energy in animals, which is true but describes a different storage polymer, not the plant starch vs. cellulose distinction.