Everything about Photosynthetic Pigment totally explained
A
photosynthetic pigment (
accessory pigment;
chloroplast pigment;
antenna pigment) is a
pigment that's present in
chloroplasts or photosynthetic
bacteria and captures the
light energy necessary for
photosynthesis.
Plants
Green plants have five closely-related photosynthetic pigments (in order of increasing polarity):IIIIIIIIIIIII
Chlorophyll a is the most common of the six, present in every plant that performs photosynthesis. The reason that there are so many pigments is that each absorbs light more efficiently in a different part of the
spectrum. Chlorophyll a absorbs well at a wavelength of about 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, which 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; 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 pigments (similar to the chlorophylls) for photosynthesis. Unlike the cyanobacteria, these bacteria don't 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 γ-
proteobacteria:
proteorhodopsin. It is similar to and probably originated from bacteriorhodopsin (see below under archaea).
Algae
Green algae,
red algae and
glaucophytes all use chlorophylls. Red algae and glaucophytes also use
phycobiliproteins, but green algae do not.
Archaea
Photosynthesis in
archaea is quite different from the systems in other domains of life. Photosynthetic archaea (the
halobacteria) use the pigment
bacteriorhodopsin which acts directly as a
proton pump when exposed to light.
Further Information
Get more info on 'Photosynthetic Pigment'.
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