In the chemistry of vision in mammals, the photosensitive substance is called

Options

A. rhodopsin
B. melanin
C. sclerotin
D. retinol

Explanation

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks for the photosensitive substance involved in the chemistry of vision in mammals.

2. **Identifying the Photosensitive Substance**: In mammals, the primary photosensitive substance responsible for vision is known as rhodopsin.

3. **Source of Rhodopsin**: Rhodopsin is produced by specialized photoreceptor cells in the retina called rod cells.

4. **Function of Rod Cells**: Rod cells are responsible for vision in low light conditions and help in the identification of shapes and movements rather than colors.

5. **Components of Rhodopsin**: Rhodopsin consists of two main components:
- **Opsin**: A protein that forms part of the rhodopsin molecule.
- **Retinal**: A derivative of vitamin A (specifically, vitamin A aldehyde) that plays a crucial role in the light absorption process.

6. **Mechanism of Action**: When light hits the rod cells, retinal changes its form (isomerization), which leads to the separation of retinal from opsin. This change triggers a biochemical cascade that results in the transmission of nerve impulses to the brain.

7. **Conclusion**: The answer to the question is that the photosensitive substance in the chemistry of vision in mammals is called **rhodopsin**.

**Final Answer**: Rhodopsin

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