A photosynthetic pigment (accessory pigment; chloroplast pigment; antenna pigment) is a

pigment A pigment is a colored material that is completely or nearly insoluble in water. In contrast, dyes are typically soluble, at least at some stage in their use. Generally dyes are often organic compounds whereas pigments are often inorganic compou ...

that is present in chloroplasts or photosynthetic

bacteria Bacteria (; singular: bacterium) are ubiquitous, mostly free-living organisms often consisting of one Cell (biology), biological cell. They constitute a large domain (biology), domain of prokaryotic microorganisms. Typically a few micrometr ...

and captures the

light Light or visible light is electromagnetic radiation that can be perceived by the human eye. Visible light is usually defined as having wavelengths in the range of 400–700 nanometres (nm), corresponding to frequencies of 750–420 te ...

energy necessary for

photosynthesis Photosynthesis is a process used by plants and other organisms to convert light energy into chemical energy that, through cellular respiration, can later be released to fuel the organism's activities. Some of this chemical energy is stored i ...

. List of photosynthetic pigments (in order of increasing polarity): * Carotene: an orange pigment *

Xanthophyll Xanthophylls (originally phylloxanthins) are yellow pigments that occur widely in nature and form one of two major divisions of the carotenoid group; the other division is formed by the carotenes. The name is from Greek (, "yellow") and (, "lea ...

: a yellow pigment * Phaeophytin ''a'':CHLOROPHYLLS
JECFA, 1987 a gray-brown pigment * Phaeophytin ''b'': a yellow-brown pigment * Chlorophyll ''a'': a blue-green pigment * Chlorophyll ''b'': a yellow-green pigment Chlorophyll ''a'' is the most common of the six, present in every plant that performs photosynthesis. Each pigment absorbs light more efficiently in a different part of the

electromagnetic spectrum The electromagnetic spectrum is the range of frequencies (the spectrum) of electromagnetic radiation and their respective wavelengths and photon energies. The electromagnetic spectrum covers electromagnetic waves with frequencies ranging fro ...

. well in the ranges of 400–450 nm and at 650–700 nm; chlorophyll ''b'' at 450–500 nm and at 600–650 nm. Xanthophyll absorbs well at 400–530 nm. However, none of the pigments absorbs well in the green-yellow region; the

diffuse reflection Diffuse reflection is the reflection of light or other waves or particles from a surface such that a ray incident on the surface is scattered at many angles rather than at just one angle as in the case of specular reflection. An ''ideal'' di ...

of the unabsorbed green light is responsible for the abundant green we see in nature.

Bacteria

Like plants, the cyanobacteria use water as an electron donor for photosynthesis and therefore liberate

oxygen Oxygen is the chemical element with the symbol O and atomic number 8. It is a member of the chalcogen group in the periodic table, a highly reactive nonmetal, and an oxidizing agent that readily forms oxides with most elements as ...

; 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. (Some cyanobacteria, the prochlorophytes, use chlorophyll b instead of phycobilin.) It is thought that the chloroplasts in plants and algae all evolved from cyanobacteria. Several other groups of bacteria use the

bacteriochlorophyll Bacteriochlorophylls (BChl) are photosynthetic pigments that occur in various phototrophic bacteria. They were discovered by C. B. van Niel in 1932. They are related to chlorophylls, which are the primary pigments in plants, algae, and cyanoba ...

pigments (similar to the chlorophylls) for photosynthesis. Unlike the cyanobacteria, these bacteria do not produce oxygen; they typically use hydrogen sulfide rather than water as the electron donor. Recently, a very different pigment has been found in some marine Gammaproteobacteria:

proteorhodopsin Proteorhodopsin (also known as pRhodopsin) is a family of transmembrane proteins that use retinal as a chromophore for light-mediated functionality, in this case, a proton pump. pRhodopsin is found in marine planktonic bacteria, archaea and euka ...

. It is similar to and probably originated from bacteriorhodopsin (see below: under #Archaea). Bacterial chlorophyll b has been isolated from Rhodopseudomonas spp. but its structure is not yet known.

Archaea

Halobacteria Haloarchaea (halophilic archaea, halophilic archaebacteria, halobacteria) are a class of the Euryarchaeota, found in water saturated or nearly saturated with salt. Halobacteria are now recognized as archaea rather than bacteria and are one of ...

use the pigment bacteriorhodopsin which acts directly as a

proton pump A proton pump is an integral membrane protein pump that builds up a proton gradient across a biological membrane A biological membrane, biomembrane or cell membrane is a selectively permeable membrane that separates the interior of a cell f ...

when exposed to light.

References

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