arrots, peaches, sweet potatoes, and other yellow vegetables rich in beta-carotehe,
a purple-orange alkene that provides our main dietary source of vitamin A.
The conversion of beta-carotene to vitamin A takes place in the mucosal cells of the small intesting,
where enzymes cut the molecule in half to yield an aicohol. Vitamin A in excess of the body's
immedlate needs is stored in the liver, from which it can be trabsported to the eye. in the eye,
vitamin A is converted into a compound called retinal,which undergoes cis-trans isomarization of C11-C12 double
bond to produce 11-cis-rethal.Reaction with the protein then produces the lightsensi tive substance rhodopsin.