Oxygen evolution



Oxygen evolution is the process of generating molecular oxides and oxoacids.

Oxygen evolution in nature

Photolytic oxygen evolution is the fundamental process by which breathable oxygen is generated in earth's biosphere. The reaction is part of the atmosphere.

Biochemical reaction

Photolytic oxygen evolution occurs via the light-dependent oxidation of water to molecular oxygen and can be written as the following simplified chemical reaction:

2H2O \longrightarrow 4e- + 4H+ + O2

The reaction requires the energy of four photophosphorylation and coupling the absorption of light energy and photolysis of water to the creation of chemical energy during photosynthesis.[1]

Oxygen-evolving complex

  Water oxidation is catalyzed by a chloride are also required for the reaction to occur.[1]

ions and one calcium ion, with one additional manganese, which are oxidized via intermediate states called S-states. The O-O bond of molecular oxygen is formed between manganese-ligated oxygen atoms at the most oxidized, or S4, state.[4]

Evolution of oxygen evolution

Oxygen production during oxygen cycle.

History of discovery

It wasn't until the end of the 18th century that Joseph Priestley discovered by accident the ability of plants to "restore" air that had been "injured" by the burning of a candle. He followed up on the experiment by showing that air "restored" by vegetation was "not at all inconvenient to a mouse." He was later awarded a medal for his discoveries that: "...no vegetable grows in vain... but cleanses and purifies our atmosphere." Priestley's experiments were followed up by Jan Ingenhousz, a Dutch physician, who showed that "restoration" of air only worked in the presence of light and green plant parts.[1]

Ingenhousz suggested in 1796 that CO2 (isotopes of oxygen from water to oxygen gas.[1]

Technological oxygen evolution

  Oxygen evolution occurs as a byproduct of electrolytic mechanism (water or solid oxide electrolysis) or chemical oxygen generators as part of their life support equipment.

References

  1. ^ a b c d e Raven, Peter H.; Ray F. Evert, Susan E. Eichhorn (2005). Biology of Plants, 7th Edition. New York: W.H. Freeman and Company Publishers, 115-127. ISBN 0-7167-1007-2. 
  2. ^ Raval M, Biswal B, Biswal U (2005). "The mystery of oxygen evolution: analysis of structure and function of photosystem II, the water-plastoquinone oxido-reductase". Photosynthesis Research 85 (3): 267-93. doi:10.1007/s11120-005-8163-4. PMID 16170631.
  3. ^ Ferreira K, Iverson T, Maghlaoui K, Barber J, Iwata S (2004). "Architecture of the photosynthetic oxygen-evolving center". Science 303 (5665): 1831-8. doi:10.1126/science.1093087. PMID 14764885.
  4. ^ Robblee J, Cinco R, Yachandra V (2001). "X-ray spectroscopy-based structure of the Mn cluster and mechanism of photosynthetic oxygen evolution". Biochimica et Biophysica Acta 1503 (1-2): 7-23. doi:10.1016/S0005-2728(00)00217-6. PMID 11115621.
  5. ^ Ananyev G, Zaltsman L, Vasko C, Dismukes G (2001). "The inorganic biochemistry of photosynthetic oxygen evolution/water oxidation". Biochimica et Biophysica Acta 1503 (1-2): 52-68. doi:10.1016/S0005-2728(00)00215-2. PMID 11115624.
 
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