Advanced Placement (AP) Biology Practice Exam

What is the primary function of polysaccharides?

1. To store genetic information.

2. To serve as a rapid energy source.

3. To provide structural support and energy storage.

4. To transport oxygen in the bloodstream.

The correct answer is: To provide structural support and energy storage.

Polysaccharides primarily serve two significant functions: providing structural support and acting as energy storage. In terms of structural support, polysaccharides like cellulose are critical components of plant cell walls, giving them rigidity and strength. This is essential for maintaining the structure of plants and contributes to the overall support of various tissues. Regarding energy storage, polysaccharides such as starch in plants and glycogen in animals serve as long-term energy reserves. Starch can be quickly mobilized by plants when energy is needed, while glycogen, stored in liver and muscle cells, can be broken down into glucose for energy during periods of high demand. Other options describe functions that do not align with the primary roles of polysaccharides. For example, storing genetic information is the primary role of nucleic acids like DNA and RNA, while a rapid energy source is typically associated with simple sugars and carbohydrates such as glucose rather than polysaccharides, which have a more complex structure and slower release of energy. Transporting oxygen in the bloodstream is a function of hemoglobin, a protein, not a polysaccharide. Thus, the correct answer reflects the essential dual role of polysaccharides in both energy storage and providing structural support in biological systems.