chlorophyll

Chlorophyll is the molecule that plants and most protists use to capture photons from the sunlight and convert it into energy useable in the cell by promoting ADP to ATP. The most important form is chlorophyll a, which does not absorb light at the green wavelength; this is why plants are green.
The peak of absorption (and of getting energy) is at wavelengths of 430 nm (blue) and 662 nm (red). The chlorophyll molecule has magnesium at its center boxed by four nitrogen atoms (a porphyrin ring).

Most photosynthetic organism have accessory pigments which capture other wavelengths, such as cartenoids and chlorophyll b. Chlorophyll b captures at wavelengths 453 nm and 642 nm and looks blue green.

Other pigments that capture light are xanthophylls e.g. zeaxanthin (a red pigment) which absorbs red light, phycoerythrin (a red pigment) and phycocyanin.

Chlo"ro*phyll (?), n. [Gr. light green + leaf: cf. F. chlorophylle.] Bot.

Literally, leaf green; a green granular matter formed in the cells of the leaves (and other parts exposed to light) of plants, to which they owe their green color, and through which all ordinary assimilation of plant food takes place. Similar chlorophyll granules have been found in the tissues of the lower animals.

© Webster 1913.