How does your skin get VitD from the sun?

Question

How does your skin get VitD from the sun?

In: Biology

Answer 1

You don’t “get” it from sunlight like you would get apples from the store. Skin cells can make it, but the reaction to do so requires UV light to work.

Its precursor is [7-dehydrocholesterol](https://en.wikipedia.org/wiki/7-Dehydrocholesterol), which can absorb UV light to react into [previtamin D3](https://en.wikipedia.org/wiki/Previtamin_D3). If you look at the molecule, one bond in the ring system is broken in this step, which is done via a photochemical reaction.