Which polysaccharide is primarily used for structural support in plants?

• A. Starch
• B. Glycogen
• C. Cellulose
• D. Chitin

Answer: (C)

Plants rely on a rigid cell wall to keep shape and resist the tug of water inside the cell. This rigidity mainly comes from cellulose, long, straight chains of glucose linked by beta-1,4 bonds. Those beta linkages force the chains to run parallel and pack tightly, enabling extensive hydrogen bonding between chains. The result is strong microfibrils that form a strong, fibrous network, giving plant tissues their tensile strength.

Starch and glycogen are built for storage, not structure. Their glucose units are connected by alpha linkages, which create flexible, branched (glycogen) or helical (starch) polymers that are easy to breakdown for quick energy. They don’t form the rigid, crystalline networks needed for cell walls. Chitin is a structural polymer in fungi and arthropods, made from N-acetylglucosamine with beta linkages, but it serves roles in those organisms rather than plants.