The alternating double and single bonds of the porphyrin ring make chlorophyll an efficient light-absorbing molecule and determine the general shape of the absorption spectrum. The phytol chain, which is almost devoid of double bonds, contributes little to the absorption spectrum. See Plant Pigments for an image of chlorophyll. As is the case for other compounds, the specific absorption maxima of any chlorophyll depends on the solvent in which it is dissolved. There are two classes of carotenoids, the carotenes and the carotenols.
All carotenoids have long isoprenoid chains, with alternating double and single bonds.
Structurally, the carotenes are composed entirely of carbon and hydrogen, whereas the carotenols also contain oxygen in the form of hydroxyl or keto groups. See Plant Pigments for an image of b -carotene. Paper Chromatography Chromatography is a technique used to separate the components of a mixture. In paper chromatography, the components of a mixture are separable into discrete zones on a sheet of filter paper. The mixture is initially spotted or streaked near one end of the paper.