Which carbohydrate is a storage polysaccharide used by plants?

• A. Starch
• B. Sucrose
• C. Lactose
• D. Glucose

Answer: (A)

Plants store energy as starch, a storage polysaccharide built from glucose units. Starch exists mainly in two forms—amylose, which is largely linear, and amylopectin, which is branched. This combination lets plants pack a lot of glucose into compact granules inside plastids such as amyloplasts in seeds and tubers, while remaining largely insoluble in water. That insolubility helps avoid osmotic problems inside cells, so the plant can keep a big reserve without pulling in extra water. When energy is needed, enzymes break starch down into glucose rapidly to fuel metabolism.

Sucidse is a disaccharide used for long-distance transport in the plant, not for storage. Lactose is a milk sugar found in mammals, not plants. Glucose is a single sugar unit, not a storage polymer.