Which of the following is a polysaccharide found in fungi, insects, and exoskeletons?

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

Answer: (C)

Chitin is a structural polysaccharide built from a modified glucose unit called N-acetylglucosamine, linked together by beta-1,4-glycosidic bonds. Those beta linkages create straight, rigid chains that can pack tightly and form strong fibers, giving both fungal cell walls and arthropod exoskeletons their strength without excessive weight. This makes chitin ideal for protection and support in fungi and in insects and other exoskeleton-bearing animals.

Cellulose is also a straight-glucose polymer with beta-1,4 linkages, but it appears in plant cell walls rather than in fungal or arthropod structures. Starch and glycogen are storage polysaccharides (alpha-linked glucose polymers) used for energy reserves in plants and animals, respectively, not for rigid, protective exteriors.