The term<unk>  is used for several related substances having the formula C40H56.<unk>  is an orange photosynthetic pigment important for photosynthesis.
It is responsible for the orange colour of the carrot and many other fruits and vegetables.  It contributes to photosynthesis by transmitting the light energy it absorbs to chlorophyll.
Chemically,<unk>  is a terpene, synthesized biochemically from eight isoprene units. It comes in two primary forms designated by characters from the Greek alphabet: alpha-carotene (α-carotene) and beta-carotene (β-carotene).  Gamma, delta and epsilon (γ, δ and ε-carotene) also exist. Beta-carotene is composed of two retinyl groups, and is broken down in the mucosa of the small intestine by beta-carotene dioxygenase to retinol, a form of vitamin A.<unk>  can be stored in the liver and converted to vitamin A as needed, thus making it a provitamin.
Carotene
Beta-carotene
Thiol
Tocopherol
Adapalene
Gallic acid
Cholic acid
Vein