Mechanism How vitamin d is synthesized from our skin

Answer 1

Vitamin D synthesis in our skin occurs through a series of chemical reactions. Here is a step-by-step mechanism of how it is synthesized:

1. Ultraviolet B (UVB) radiation from sunlight penetrates the epidermal layer of our skin.

2. When UVB radiation reaches a molecule called 7-dehydrocholesterol (a precursor of cholesterol) present in the skin cells, it absorbs the radiation and undergoes a process called photoconversion.

3. Photoconversion causes 7-dehydrocholesterol to rearrange its structure and transform into previtamin D3 (also known as cholecalciferol).

4. Previtamin D3 is an unstable compound and undergoes a thermal isomerization reaction. It turns into vitamin D3 (cholecalciferol) spontaneously or with the help of body heat.

5. From the skin cells, vitamin D3 enters the bloodstream.

6. In the liver, vitamin D3 undergoes hydroxylation (addition of a hydroxyl group) by an enzyme called 25-hydroxylase. This results in the formation of 25-hydroxyvitamin D3 (calcidiol or calcifediol).

7. 25-hydroxyvitamin D3 then enters the kidneys, where it undergoes another hydroxylation step by an enzyme called 1-alpha-hydroxylase. This final step leads to the formation of 1,25-dihydroxyvitamin D3 (calcitriol), which is the biologically active form of vitamin D.

Once calcitriol is formed, it acts as a hormone, exerting various physiological effects throughout the body to regulate calcium and phosphate metabolism, bone health, and immune function.

It's important to note that this mechanism primarily refers to the synthesis of vitamin D3 from sunlight exposure. However, vitamin D can also be obtained from dietary sources, such as fortified foods or supplements, which bypass this synthesis process.