Beta carotene

In my spare time, for fun, sometimes I read up on nutrition. My latest favorite is beta carotene, a compound that the body cuts into half to form vitamin A. Beta carotene has a long hydrocarbon chain, with double bonds. The body uses beta carotene to produce retinal, and retinal binds to the protein opsin to form rhodopsin, a pigment for vision (light hits one of the double bonds and twists it from a cis to trans bond, and this generates a visual response). For more information on this, see the Wikipedia links.
According to Wikipedia, beta carotene is a terpenoid, and terpenoids help to attach proteins to cell membranes. Thus, beta carotene is not just for vision.

And this is what happens when I have too much free time on my hands...
Thank you, Wikipedia...