Exposure to sun is required for synthesis of vitamin D in

Options

A. Adipose tissue
B. Liver
C. Gall bladder
D. skin

Answer

To answer the question regarding which part of the body requires exposure to the sun for the synthesis of vitamin D, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Vitamin D Synthesis**: Vitamin D is a fat-soluble vitamin that is crucial for maintaining healthy bones and immune function. It can be obtained from dietary sources or synthesized in the body.

2. **Role of Sunlight**: The synthesis of vitamin D in the body primarily occurs when the skin is exposed to sunlight, specifically ultraviolet B (UVB) rays.

3. **Location of Synthesis**: The skin contains a precursor molecule called 7-dehydrocholesterol, which is converted to vitamin D when exposed to UVB rays from the sun.

4. **Process of Synthesis**: When UVB rays hit the skin, they provide the energy needed to convert 7-dehydrocholesterol into previtamin D3, which is then transformed into vitamin D3 (cholecalciferol) through a heat-dependent process.

5. **Final Activation**: The vitamin D3 produced in the skin is then transported to the liver and kidneys, where it is further processed into its active form, calcitriol.

6. **Conclusion**: Therefore, the correct answer to the question is that exposure to the sun is required for the synthesis of vitamin D in the **skin**.

### Final Answer:
**Skin**

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