[Campbell Biology P.120] Which of the following statements accurately describes a key struct... | Practice Question
Which of the following statements accurately describes a key structural and functional difference between starch and cellulose, according to the provided text?
A: Starch is formed from alpha-glucose monomers and is always unbranched, while cellulose is formed from beta-glucose monomers and is highly branched.
B: Starch monomers are linked by 1-4 alpha-glycosidic bonds, allowing for helical structures and energy storage, whereas cellulose monomers are linked by 1-4 beta-glycosidic bonds, forming straight, unbranched chains for structural support.
C: Both starch and cellulose are extensively branched polysaccharides used for energy storage in plants, but only starch is digestible by human enzymes.
D: Cellulose is the main component of plant cell walls and is digestible by human enzymes due to its unique beta-glycosidic linkages, while starch is not.
Explanation
The text states that starch monomers are in the alpha configuration and are linked by 1-4 alpha-glycosidic bonds, leading to largely helical shapes for efficient storage. In contrast, cellulose monomers are in the beta configuration, linked by 1-4 beta-glycosidic bonds, forming straight, unbranched chains that provide strength for plant cell walls. Human enzymes can digest starch alpha linkages but not cellulose beta linkages due to these structural differences.