Photosynthetic pigment

List of photosynthetic pigments (in order of increasing polarity): Chlorophyll a is the most common of the six, present in every plant that performs photosynthesis.

Like plants, the cyanobacteria use water as an electron donor for photosynthesis and therefore liberate oxygen; they also use chlorophyll as a pigment.

In addition, most cyanobacteria use phycobiliproteins, water-soluble pigments which occur in the cytoplasm of the chloroplast, to capture light energy and pass it on to the chlorophylls.

Unlike the cyanobacteria, these bacteria do not produce oxygen; they typically use hydrogen sulfide rather than water as the electron donor.

Halobacteria use the pigment bacteriorhodopsin which acts directly as a proton pump when exposed to light.