Which polymer serves as the storage form of glucose in animals?

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

Answer: (D)

Glucose is stored in animals as glycogen, a highly branched polysaccharide made of glucose units connected by alpha-1,4 linkages with alpha-1,6 branches. This structure allows rapid synthesis and quick, controlled release of glucose when needed, which is essential for short-term energy during activity. Glycogen is stored mainly in the liver and muscles, supporting blood glucose levels and providing immediate energy to muscles during contraction. In contrast, cellulose is a structural plant polymer with beta-1,4 linkages; starch is another plant storage polymer with fewer branches and slower mobilization; chitin is a structural polymer in fungi and arthropods, composed of N-acetylglucosamine. Because of its branching and solubility, glycogen is best suited for efficient glucose storage in animals.