The role of photosynthetic pigments

The first stage of reformation of light energy into the chemical is called absorbtion of light. The pigmentis the compound, which absorbs the visible light. Some pigments absorb the light of any length of wave and that is why it seams black. The other ones – the light of only certain length of wave, and the rest of light are let pass or reflected by pigments.

Pigments, which take part in the process of photosynthesis are: chlorophylls, carotinoidsandphycobylines.

Chlorophyll – is the pigment, that causes the green color of leaves; it absorbs, in general, violet and blue rays, and also red light. There are some forms of chlorophyll, which differ by molecular structure. Chlorophyll A is characteristic for all photosynthesis eucaryot and cianobacteria. The vessel’s plant, mosses, green and euglens seaweeds contain chlorophyll B. When the molecule of chlorophyll B absorbs the light, then excited, electron pass its energy to chlorophyll A, which after that in the process of photosynthesis reforms it into the energy of bonds.

Chlorophyll A – is a big molecule, which contains (in the center) scarlet pink magnesium. The long chains of carbon-hydrate are attached to the ring, and serve as anchor for attachment of molecule in internal membranes of chloroplasts.

Molecules of pigment absorb the light energy, that is why electrons rise on the higher energetic level, and then come down on the lower one, then it can have such continuous like:

1. The energy of electron disperses in the form of warmth ;

2. Immediately it evolves in a light energy form of greater length of wave (this phenomenon is called phluoriscencia (phosphorescenia);

3.The energy stores in a form of chemical bonds, that happens in the process of photosynthesis. Chlorophyll can refabricate the energy of light into chemical one only in the complex with the certain albumens, situated in the tylacoids.

During reformation of energy other types of pigments – carotynoids and phycobylines also take part. The energy, absorbed by auxiliary pigments, must be transformed into chlorophyll A; replace it in the process of photosynthesis cannot take place.

Carotynoids are red, orange or yellow fat-dissolved pigments, found in the chloroplasts and in cianobacteria. Like chlorophyll, carotynoids of chloroplasts deepen in the tylacoid’s membranes. In chloroplasts two groups of carotynoids are usually present - carotenes and xanthophylls. Betha- carotene is a general source of vitamin A. Xanthophylls are yellow pigments that absorb light energy in other parts of the spectrum and pass it on to chlorophyll. Carotenes are orange pigments that perform the same function. These two pigments are present in the most green plants but in lesser amounts than chlorophyll, which usually masks their presence. In the fall when many leaves stop producing chlorophyll, xanthophyll and carotene become more prominent.

Phycobylinesare present in cianobacteria and in chloroplasts of the Red Sea weeds. Unlike carrotynoids, the phycobylines dissolve in water.