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Photorespiration may be necessary for the assimilation of nitrate from soil. Thus, a lowering in photorespiration by genetic engineering or because of increasing atmospheric carbon dioxide may not benefit plants as has been proposed. [14] Several physiological processes may be responsible for linking photorespiration and nitrogen assimilation.
Free oxygen is produced in the biosphere through photolysis (light-driven oxidation and splitting) of water during photosynthesis in cyanobacteria, green algae, and plants. During oxidative phosphorylation in cellular respiration, oxygen is reduced to water, thus closing the biological water-oxygen redox cycle.
In scientific literature, the Mehler reaction often is used interchangeably with the Water-Water Cycle [2] to refer to the formation of H 2 O 2 by photosynthesis. Sensu stricto, the Water Water Cycle encompasses the Hill reaction, in which water is split to form oxygen, as well as the Mehler Reaction, in which oxygen is reduced to form H 2 O
Countercurrent flow occurs when deoxygenated blood moves through the gill in one direction while oxygenated water moves through the gill in the opposite direction. This mechanism maintains the concentration gradient thus increasing the efficiency of the respiration process as well and prevents the oxygen levels from reaching an equilibrium .
The high-energy oxidized tyrosine gives off its energy and returns to the ground state by taking up a proton and removing an electron from the oxygen-evolving complex and ultimately from water. [4] Kok's S-state diagram shows the reactions of water splitting in the oxygen-evolving complex.
The adaptations of C4 plants provide an advantage over the C3 pathway, which loses efficiency due to photorespiration. [22] The ratio of photorespiration to photosynthesis in a plant varies with environmental conditions, since decreased CO 2 and elevated O 2 concentrations would increase the efficiency of photorespiration. [ 20 ]
The opposite process occurs in the pulmonary capillaries of the lungs when the PO 2 rises and PCO 2 falls, and the Haldane effect occurs (release of CO 2 from hemoglobin during oxygenation). This releases hydrogen ions from hemoglobin, increases free H + concentration within RBCs, and shifts the equilibrium towards CO 2 and water formation from ...
Photosynthetic water splitting (or oxygen evolution) is one of the most important reactions on the planet, since it is the source of nearly all the atmosphere's oxygen. Moreover, artificial photosynthetic water-splitting may contribute to the effective use of sunlight as an alternative energy source.