Which of the following polysaccharide gives blue colour with lodine

Options

A. Glycogen
B. Starch
C. Cellulose
D. Chitin

Answer

To determine which polysaccharide gives a blue color with iodine, we can follow these steps:

### Step 1: Understand the Polysaccharides
First, let's identify the polysaccharides mentioned in the question:
- Glycogen
- Starch
- Cellulose
- Chitin

### Step 2: Know the Reaction with Iodine
Iodine is known to form a blue complex with starch. This occurs because starch has a helical structure that can trap iodine molecules.

### Step 3: Analyze Each Option
1. **Glycogen**: While glycogen is a polysaccharide, it does not give a blue color with iodine like starch does.
2. **Starch**: Starch is known to give a blue color with iodine due to its helical structure.
3. **Cellulose**: Cellulose does not give a blue color with iodine because it lacks the helical structure that can trap iodine.
4. **Chitin**: Chitin also does not give a blue color with iodine.

### Step 4: Conclusion
Based on the analysis, the only polysaccharide that gives a blue color with iodine is **starch**.

### Final Answer
The correct answer is **starch**.

---