Editing Photosynthetic pigment

{{short description|Type of molecule}}
{{Refimprove|date=December 2013}}
[[File:Electromagnetic spectrum 2.jpg|thumb|upright=1.8| {{center|[[Electromagnetic spectrum]] – wavelengths in metres}}]]

A '''photosynthetic pigment''' ('''accessory pigment'''; '''chloroplast pigment'''; '''antenna pigment''') is a [[biological pigment|pigment]] that is present in [[chloroplast]]s or photosynthetic [[bacterium|bacteria]] and captures the [[light]] energy necessary for [[photosynthesis]].

List of photosynthetic pigments (in order of increasing polarity):
*[[Carotene]]: an orange pigment
*[[Xanthophyll]]: a yellow pigment
*[[Phaeophytin|Phaeophytin ''a'']]:<ref name=phaeophytin>[http://www.fao.org/ag/agn/jecfa-additives/specs/Monograph1/Additive-128.pdf CHLOROPHYLLS], JECFA, 1987</ref> a gray-brown pigment
*[[Phaeophytin|Phaeophytin ''b'']]:<ref name=phaeophytin /> a yellow-brown pigment
*[[Chlorophyll a|Chlorophyll ''a'']]: a blue-green pigment
*[[Chlorophyll b|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]]. {{as written|Chlorophyll ''a'' absorbs}} well in the ranges of 400–450&nbsp;nm and at 650–700&nbsp;nm; chlorophyll ''b'' at 450–500&nbsp;nm and at 600–650&nbsp;nm. Xanthophyll absorbs well at 400–530&nbsp;nm. However, none of the pigments<ref>{{cite journal |last1=Virtanen |first1=Olli |last2=Constantinidou |first2=Emanuella |last3=Tyystjarvi |first3=Esa |title=Chlorophyll does not reflect green light – how to correct a misconception |url=https://www.tandfonline.com/doi/full/10.1080/00219266.2020.1858930 |journal=Journal of Biological Education |date=2022 |volume=56 |issue=5 |pages=552–559 |publisher=Taylor & Francis Online |doi=10.1080/00219266.2020.1858930 |access-date= 26 January 2024|doi-access=free }}</ref><ref>{{cite journal |last1=Gruszecki |first1=Wieslaw |last2=Grudzinski |first2=Wojciech |last3=Banaszek-Glos |first3=Agnieszka |last4=Matula |first4=Magdalena |last5=Kernen |first5=Peter |last6=Krupa |first6=Zbigniew |last7=Sielewiesiuk |first7=Jan |title=Xanthophyll pigments in light-harvesting complex II in monomolecular layers: localisation, energy transfer and orientation |url=https://core.ac.uk/download/pdf/81974593.pdf |website=Connecting Repositories |publisher=Elservier |pmid=10393259 |archive-url=https://web.archive.org/web/20190419065642/https://core.ac.uk/download/pdf/81974593.pdf |access-date=27 January 2024|archive-date=2019-04-19 }}</ref> absorb well in the green-yellow region; the [[diffuse reflection]] of the unabsorbed green light is responsible for the abundant green seen in nature. 

==Bacteria==
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 [[phycobiliprotein]]s, 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]] 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]]. It is similar to and probably originated from bacteriorhodopsin (see below: under [[#Archaea]]).

==Archaea==
{{see|Archaea}}
[[Halobacteria]] use the pigment [[bacteriorhodopsin]] which acts directly as a [[proton pump]] when exposed to light.

==References==
{{reflist}}

[[Category:Photosynthetic pigments| ]]