Amylase is an enzyme that breaks down starch. Why can the same enzyme not break down cellulose?

• A. The enzyme cannot attack cellulose because of its helical shape.
• B. Cellulose molecules are much too large.
• C. Starch is made of glucose; cellulose is made of fructose.
• D. The bonds between the monosaccharide monomers in cellulose are much stronger.
• E. The monosaccharide monomers in cellulose are bonded together differently than those in starch.

Answer: (E)

Verified step by step guidance

1. Understand the role of amylase: Amylase is an enzyme that catalyzes the breakdown of starch into sugars. It specifically targets the glycosidic bonds in starch.
2. Identify the structure of starch: Starch is composed of glucose monomers linked by α-1,4-glycosidic bonds, which form a helical structure that amylase can easily access and break down.
3. Examine the structure of cellulose: Cellulose is also composed of glucose monomers, but they are linked by β-1,4-glycosidic bonds, resulting in a straight, rigid structure.
4. Recognize the difference in bond types: The β-1,4-glycosidic bonds in cellulose create a different three-dimensional structure compared to the α-1,4-glycosidic bonds in starch, making it inaccessible to amylase.
5. Conclude why amylase cannot break down cellulose: The enzyme amylase is specific to the α-1,4-glycosidic bonds found in starch and cannot interact with the β-1,4-glycosidic bonds in cellulose due to the difference in molecular structure.