Photosynthesis carbon dioxide assimilation

Joshi H. M. and Tabita F. R. (1996) A global two-way component signal transduction system that integrates the control of photosynthesis, carbon dioxide assimilation and nitrogen fixation. Proc. Natl. Acad. Sci. USA 93, 14515-14520. 

B.B. Buchanan. 1992. Carbon dioxide assimilation in oxygenic and anoxygenic photosynthesis P/zotoyywt/z. Res. 33 147-162. 

Fig.2.6 Overall design of photosynthesis. The light reactions make ATP and NADPH to be used in the carbon dioxide assimilation reactions that form fructose and glucose (Modified from Fig. 19-37 in Lehninger Principles of Biochemistry. D.L. Nelson M.M. Cox, 4th Ed. 2005. W.H. Freeman Co., New York)...

Carbon dioxide assimilation, carbon fixation the incorporation of COj into larger organic compounds. C.d.a. is sometimes used as a synonym for photosynthesis, but strictly speaking photosynthesis is a series of reactions that generate the ATP and NAD(P)H required to drive the reactions of Cd.a. By far the greatest amount of C. d. a. occurs in green plants and cyanobacteria. Most of this occurs in the... 

Photosynthetic earboxylation the enzymatic fixation of carbon dioxide in photosynthesis. In C-3 plants, the photosynthetic earboxylation enzyme is ri-bulose iirphosphate carboxylase (EC 4.1.1.39). In C-4 plants it is phosphoeno/pyruvate carboxylase (EC 41.1.31). P. c. is the first step of carbon dioxide assimilation in photosynthesis, and one of the dark reactions. 

AO3 Molecules of oxygen liberated during photosynthesis —ACO molecules of carbon dioxide assimilated... 

Andy Benson obtained his Ph.D. in organic chemistry from the California Institute of Technology. He subsequently joined the blo-organlc chemistry group at the Lawrence Radiation Laboratory of the University of California at Berkeley at what proved to be a very productive time. Together with Calvin and Bassham he was responsible for the complete elucidation of the pathway of carbon dioxide assimilation in photosynthesis. 

Stokes DM and Walker DA (1972) Photosynthesis by isolated chloroplasts. Inhibition by DL-glyceraldehyde of carbon dioxide assimilation, Biochem.J 128, 1147-1157 ... 

Fig. 5.1, Relationship of carbon dioxide concentration to the rate of carbon dioxide assimilation at various light intensities (shown against each curve in kerg/cm /sec). (Data for whole plants of Triticum sativa (wheat) after W. H. Hoover, E. S. Johnston and F. S. Brackett, Smithsonian Inst. Publ. Misc. Collections, 87 No. 16, 1933.) (From E. I. Rabinowitch, Photosynthesis, vol. 2, pt. 1, Interscience Pub. Inc., New York, 1951.)...

Fig. 5.7. Simplified version of the Calvin cycle showing the path of carbon dioxide assimilation in photosynthesis.

Carbon dioxide assimilation via the Calvin cycle requires a supply of reduced co-enzyme and of ATP. This suggests that the photochemical reactions of photosynthesis involve the conversion of electromagnetic energy into the chemical energy of the terminal pyrophosphate bond of ATP and the reduced form of the coenzyme. 

The outcome of the photosynthesis processes is ultimately similar in all green plants carbon dioxide from the atmosphere is taken up by the plants, where it reacts with water to form carbohydrates and oxygen the carbohydrates are assimilated by the plants while the oxygen is released to the atmosphere (see Textbox 53). Extensive studies have shown that the conversion of carbon dioxide and water into carbohydrates in different plants may follow, however, one of three different photosynthetic pathways, which are usually referred to as the C3, C4, and CAM paths. Each type of plant follows just one of these three pathways. 

The photoreductive synthetic process that promotes the assimilation of carbon dioxide into carbohydrates, other reduced metabolites, as well as ATP (synthesis of the latter is termed photophosphorylation). Photosynthesis is the primary mechanism for transducing solar energy into biomass, and green plants utilize chlorophyll a to capture a broad spectrum of solar radiant energy reaching the Earth s surface. Photosynthetic bacteria typically produce NADPH, the reductive energy of which is converted to ATP. 

The input chemicals are carbon dioxide and water, while the output is oxygen and carbohydrates. The latter serve as a feedstock for other organic products such as wood, coal, oil, and gas constituting the World s fossil fuel reserves. It is estimated that about lO tons of carbon dioxide are assimilated annually by plants on Earth, whereby the amount of solar energy harvested by natural photosynthesis is 3 x 10 kJ, corresponding to the continuous generation of 90000 GW of electrical power. 

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