Question

All of the following are storage carbohydrates except:

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

Hint:

The key difference between storage and structural glucose polymers lies in their glycosidic bonds:
- Storage carbohydrates (starch, glycogen) use \( \alpha \)-glycosidic bonds, which are easily hydrolyzed by enzymes.
- Structural carbohydrates (cellulose) use \( \beta \)-glycosidic bonds, which form highly stable, rigid sheets resistant to enzymatic cleavage.

Answer 1

The Correct Option is C

Step 1: Understanding the Concept:
Carbohydrates are organic macromolecules classified based on their biological functions into storage carbohydrates and structural carbohydrates.
Storage carbohydrates serve as energy reserves, while structural carbohydrates provide mechanical strength to cell walls and tissues.

Step 2: Detailed Explanation:
Let us analyze each of the options provided:
- (A) Starch: This is the primary storage polysaccharide in plants.
It is composed of amylose and amylopectin, serving as an energy reserve in seeds, tubers, and roots. Thus, it is a storage carbohydrate.
- (B) Glycogen: This is the primary storage polysaccharide in animals and fungi.
It is stored in the liver and muscle tissues to maintain blood glucose levels. Thus, it is a storage carbohydrate.
- (C) Cellulose: This is a linear polymer of \( \beta \)-1,4-linked glucose units.
It forms the structural framework of plant cell walls, providing rigidity and tensile strength.
Plants cannot easily degrade or mobilize cellulose to use as an energy source.
Therefore, it is classified as a structural carbohydrate, making it the correct exception.
- (D) Amylase: Note that amylase is actually an enzyme that hydrolyzes starch.
However, even if interpreted as "amylose" (a component of starch), amylose is a storage polysaccharide.
Since cellulose is the definitive structural carbohydrate, it is the correct exception.

Step 3: Final Answer:
Cellulose is a structural carbohydrate, not a storage carbohydrate.