What pigments take part in photosynthesis?
The green chlorophyll a & b
Chlorophylla-a is the primary pigment for photosynthesis in plants, but the range of light absorption is extended by chlorophyll-b, beta-carotene (a carotenoid).
Pigments are chemical compounds capable of absorbing certain wavelengths of light energy depending upon their color. A pigment will look the color of whatever wavelength it does NOT absorb, In photosynthesis there are two major classes of pigments 1) Chlorophyll-- which absorbs many light wavelenghts EXCEPT green- which comes in two forms, chlorophyll a which is possessed by most plants, algae and cyanobacteria and chlorophyll b found in both plants and green algae. 2) Carotenoids- pigments which look orange and brown and pass the energy on to chlorophyll for use in photosynthesis, hence their name of accessory pigments.
Photosynthesis in plants is dependent upon capturing light energy in the pigment chlorophyll.This chlorophyll resides mostly in the chloroplasts and gives leaves their green color. The range of light absorption in leaves is extended by some accessory pigments such as the carotenoids, but does not cover the entire visible range - that would make the leaves black! Some plants and plantlike organisms have developed other pigments to compensate for low light or poor use of light. Cyanobacteria and red algae have phycocyanin and allophycocyanin as accessory pigments to absorbe orange light. They also have a red pigment called phycoerythrin that absorbs green light and extends the range of photosynthesis. The red pigment lycopene is found in vegetables. Some red algae are in fact nearly black, so that increases their photosynthetic efficiency. Brown algae have the pigment fucoxanthin in addition to chlorophyll to widen their absorption range.
There are three basic classes of pigments. Chlorophylls are greenish pigments which contain a porphyrin ring. This is a stable ring-shaped molecule around which electrons are free to migrate. Because the electrons move freely, the ring has the potential to gain or lose electrons easily, and thus the potential to provide energized electrons to other molecules. This is the fundamental process by which chlorophyll captures the energy of sunlight. There are several kinds of chlorophyll, the most important being chlorophyll a. This is the molecule which makes photosynthesis possible, by passing its energized electrons on to molecules which will manufacture sugars. All plants, algae, and cyanobacteria which photosynthesize contain chlorophyll a. A second kind of chlorophyll is chlorophyll b, which occurs only in green algae and in the plants. A third form of chlorophyll which is common is (not surprisingly) called chlorophyll c, and is found only in the photosynthetic members of the Chromista as well as the dinoflagellates. The differences between the chlorophylls of these major groups was one of the first clues that they were not as closely related as previously thought.....
