Which one of the following statements is not correct ?

Options

A. Retinal is the light absorbing portion of visual photo pigments
B. In retina the rods have the photopigment rhodopsin while cones have three different photopigments
C. Retinal is a derivative of Vitamin C
D. Rhodopsin is the purplish red protein present in rods only

Answer

To determine which statement is not correct, we will analyze each of the provided statements regarding retinal and its role in vision.

### Step-by-Step Solution:

1. **Analyze the First Statement**:
- The first statement claims that "retinal is the light-absorbing portion of the visual photopigments."
- **Explanation**: Retinal is indeed a derivative of vitamin A and functions as a chromophore in visual photopigments, allowing the conversion of light energy into chemical signals for vision.
- **Conclusion**: This statement is **correct**.

2. **Analyze the Second Statement**:
- The second statement states that "in the retina, the rods have photopigment rhodopsin while cones have three different photopigments."
- **Explanation**: Rods contain rhodopsin, which is responsible for vision in low light, while cones have three types of photopigments that respond to different wavelengths of light (short, medium, and long).
- **Conclusion**: This statement is also **correct**.

3. **Analyze the Third Statement**:
- The third statement claims that "retinal is a derivative of vitamin C."
- **Explanation**: This is incorrect. Retinal is actually a derivative of vitamin A (specifically retinol), not vitamin C.
- **Conclusion**: This statement is **incorrect**.

4. **Analyze the Fourth Statement**:
- The fourth statement mentions that "rhodopsin is the purplish-red protein which is present in the rods only."
- **Explanation**: Rhodopsin is indeed a purplish-red protein found in rod cells, which are responsible for vision in dim light. It is not found in cone cells.
- **Conclusion**: This statement is **correct**.

### Final Conclusion:
The statement that is **not correct** is the third one: "retinal is a derivative of vitamin C."