- C3 carbon fixation
c3 carbon fixation is a
metabolic pathway forcarbon fixation inphotosynthesis . This process convertscarbon dioxide andribulose bisphosphate (RuBP, a 5-carbon sugar) into3-phosphoglycerate through the following reaction::6 CO2 + 6 RuBP → 12
3-phosphoglycerate This reaction occurs in all plants as the first step of the
Calvin cycle . In c4 plants, carbon dioxide is drawn out ofmalate and into this reaction rather than directly from theair .Plant s that survive solely on c3 fixation (c3 plants) tend to thrive in areas wheresunlight intensity is moderate,temperature s are moderate,carbon dioxide concentrations are around 200 ppm or higher, andground water is plentiful. The c3 plants, originating duringMesozoic andPaleozoic era, predate the c4 plants and still represent approximately 95% of Earth's plant biomass. c3 plants lose 97% of the water taken up through their roots to transpiration.cite journal
author = Raven, J.A.
coauthors = Edwards, D.
year = 2001
title = Roots: evolutionary origins and biogeochemical significance
journal = Journal of Experimental Botany
volume = 52
issue = 90001
pages = 381–401
doi = 10.1093/jexbot/52.suppl_1.381
doi_brokendate = 2008-06-21]c3 plants must be in areas with high concentrations of carbon dioxide because
RuBisCO often incorporates an oxygen molecule into the RuBP, instead of a carbon dioxide molecule. This breaks the RuBP into a three-carbon sugar that can remain in the Calvin cycle, and two molecules ofglycolate which is oxidized into carbon dioxide, wasting the cell's energy. High concentration of carbon dioxide lowers the chance that RuBisCO incorporates an oxygen molecule. c4 and CAM plants have adaptations that allow them to survive in areas where the plant cannot take in a lot of carbon dioxide.The
isotopic signature of c3 plants shows higher degree of 13C depletion than the c4 plants.ee also
*
C4 carbon fixation
*CAM photosynthesis References
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