carrots are rich in β-caotene, a purple-orange alkene that is an excellent dietary source of vitamin A.
β-Carotene is coverted to vitamin A by enzymes in the liver, oxidized to an aldehyde called all-trans-retinal, and them ismerized by a change in geometry of the c11-c12 double bond to produce 11-cis-retinal, the light-sensitive pig-ment on which the visual sytems of all living things are based.