Carbon Fixation

Biological carbon fixation or сarbon assimilation is the process by which inorganic carbon (particularly in the form of carbon dioxide) is converted to organic compounds by living organisms. See also [1].

Organisms that grow by fixing carbon are called autotrophs, which include photoautotrophs (which use sunlight), and lithoautotrophs (which use inorganic oxidation).

Seven autotrophic carbon fixation pathways are known.

Calvin cycle

3 CO₂ + 6 NADPH + 6 H⁺ + 9 ATP + 5 H₂O → glyceraldehyde-3-phosphate (G3P) + 6 NADP⁺ + 9 ADP + 8 P_i (P_i = inorganic phosphate)

Step 1

The enzyme RuBisCO catalyses the carboxylation of ribulose-1,5-bisphosphate, RuBP, a 5-carbon compound, by carbon dioxide (a total of 6 carbons) in a two-step reaction.