Which of the following statements is not correct regarding chitin ?

Options

A. It is a storage polysaccharide.
B. It is a homopolysaccharide.
C. It is a constituent of arthropod exoskeleton and fungal cell wall.
D. It is the second most abundant carbohydrate on earth.

Explanation

To determine which statement is not correct regarding chitin, we will analyze the properties and characteristics of chitin step by step.

### Step 1: Understand what chitin is
Chitin is a polysaccharide that is primarily composed of N-acetylglucosamine monomers. It is classified as a homopolysaccharide because it consists of only one type of monomer.

**Hint:** Remember that homopolysaccharides consist of only one type of sugar unit.

### Step 2: Identify the role of chitin
Chitin serves as a structural component in various organisms. It is most notably found in the exoskeletons of arthropods (such as insects, crustaceans, and arachnids) and in the cell walls of fungi.

**Hint:** Think about where you might find chitin in nature, especially in relation to arthropods and fungi.

### Step 3: Classify chitin
Chitin is not a storage polysaccharide; rather, it is a structural polysaccharide. Storage polysaccharides include substances like glycogen and starch, which serve as energy reserves.

**Hint:** Differentiate between structural and storage polysaccharides by considering their functions in organisms.

### Step 4: Evaluate the statements
Now, let's evaluate the statements one by one:
1. **"It is a storage polysaccharide."** - This statement is incorrect because chitin is a structural polysaccharide.
2. **"It is a homopolysaccharide."** - This statement is correct.
3. **"It is a constituent of arthropods' exoskeleton and fungal cell wall."** - This statement is correct.
4. **"It is the second most abundant carbohydrate on earth."** - This statement is also correct.

### Conclusion
The statement that is not correct regarding chitin is the first one: "It is a storage polysaccharide."

**Final Answer:** The incorrect statement is: "It is a storage polysaccharide."

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