Re: what class of hydrocarbons does B-carotene and lycopene belong to?

Hi Beth,

Beta-Carotene (aka B-Carotene) and Lycopene are both examples of carotenoids, a diverse group of pigment molecules that are found in many fungi, plants, animals and bacteria. Carotenoid compounds are usually red, yellow, or orange in color, and are responsible for the vibrant colors of autumn foliage, the bright pink color associated with flamingo plumage, the deep red flesh of salmon, and the bright red and yellow colors of ripe fruits and vegetables (e.g. tomatoes and bell peppers). The words carotene and carotenoid are derived from the word carrot, as the deep orange color of a carrot is due to the high concentration of B-Carotene in carrots.

Carotenoids vary widely in structure and chemistry, but they are all constructed from 5- carbon isoprenoid subunits like the one shown in the figure below. This repeating structure allows us to classify carotenoid compounds as polyenes.

	In your question, you suggested that carotenoids are hydrocarbons, but many of them are oxidized, and it is probably best to think of molecules like Lycopene and B- Carotene simply as carotenoids as opposed to hydrocarbons.

Perhaps the most famous carotenoids are oxidized, as you can see in the figure below describing the structure of all-trans retinol (aka Vitamin A) and all-trans retinoic acid.

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You can find quite a bit of information about carotenoids by using MadSci Search Engine, and you should be able to find in detailed discussions about carotenoid structure and function in any college-level biochemistry textbook.