photosynthesis (rus. фотосинтез) — chemical process of generating organic substance from non-organic using sunlight energy, which occurrs in green plants and some bacteria.

Description

Photosynthesis involves pigments (chlorophylls in plants, bacteriochlorophyll in bacteria). Photosynthesis is based on redox reactions, where electrons are transferred from the donor (, ) to the acceptor () accompanied with the formation of reduced compounds (carbohydrates, ) and the release of (in case of the electron donor being (from ) и etc.

The equation of photosynthesis is given by


where is the reducer, which is oxidised to . In higher plants, algae and cyanobacteria, water is the reducer and oxygen is the product of photosynthesis. This is called oxygenic photosynthesis.

The photosynthesis process involves many stages, which differ in energy and duration. The structure of photosynthetic units and the number of photosynthesis stages are different for different organisms; however, there are three common basic processes:

- light absorption by photoantenna and the transfer of electronic excitation energy from the antenna to the reaction site;

- electron transfer in the reaction site and the charge separated state;

- chemical reactions that lead to the synthesis of substances - primary ones (reduced form of nicotineamide adenine dinucleotide phosphate - NADP and adenosine triphosphate - ATP) and end products of photosynthesis.

Energy in photosynthesis is converted from one form to another as follows: light energy → electron energy → electrical energy → chemical energy. All the components of natural photosynthetic devices, like photoantennae, the reaction site, etc. - are protein nanostructures.

Photosynthesis is one of the most common processes on Earth, it underlies a natural cycle of carbon, oxygen and other elements. Photosynthesis is the basis of material and energy basis of all life on the planet. Photosynthesis leads to binding as organic matter of about 8 · 1,010 tons of carbon, forming of up to 1,011 tons of cellulose annually. Through photosynthesis, land plants produce about 1.8 · 1,011 tons of dry biomass per year, and roughly the same amount of plant biomass is produced annually in the oceans. Rainforests’ contribution amounts to 29% of the total land photosynthesis production, and all types of forests give up to 68%. Photosynthesis of higher plants and algae is the only source of atmospheric O2.

Author

  • Eremin Vadim V.

Sources

  1. Rubin A. B. Biophysics (in Russian). — Мoscow, 1999. V.1, ch. 13; V. 2, ch. 27.
  2. Photosynthesis// Chemical encyclopedia (in Russian) V. 5. — Мoscow: Bol'shaja Rossijjskaja ehnciklopedija, 1998. 175–179 pp.
  3. Hall D. O., Rao K. K. Photosynthesis.5th edition — Cambridge University Press, Cambridge. 1994. — 211 pp.

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