Calvin-Benson Cycle (Arabidopsis thaliana)

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ChloroplastCO2 + H2ONADP+O2fructose-1,6-bisphosphataseNADPHCO2H+phosphoribulokinaseH2CO3carbonic anhydrase 22-phosphoglycolatesedoheptulose 1,7-bisphosphatefructose 6-phosphate1,3-bisphosphoglyceratexyluloase-5-phosphateATPfructose-1,6-bisphosphataseADPerythrose 4-phosphatePiribulose 5-phosphate 3-epimeraseribose 5-phosphateribulose 5-phosphate3-phosphoglyceratesedoheptulose 1,7-bisphosphatasesedoheptulose 7-phosphateRuBisCO activaseribulose-1,5-bisphosphateGlycolysisH2Ofructose-1,6-bisphosphatecarbonic anhydrase 1glyceraldahyde-3-phosphateDihydroxyacetone phosphatetriose phosphate isomeraseH2OH2OPifructose 1,6-bisphosphatealdolase 1fructose 6-phosphatePiH2Oaldolase 2Photorespiration2H+Starch MetabolismRuBisCO SSU1ARuBisCO LSURuBisCO SSU1BRuBisCO SSU2BRuBisCO SSU3Bphosphoglycerate kinase 2phosphoglycerate kinase 1glyceraldehyde-3-phosphate dehydrogenase 1glyceraldehyde-3-phosphate dehydrogenase 2aldolase 1aldolase 2transketolase 1transketolase 2aldolase 1aldolase 2transketolase 1transketolase 2ribulose 5-phosphate isomerase 3ribulose 5-phosphate isomerase 4


The Calvin cycle, Calvin–Benson–Bassham (CBB) cycle, reductive pentose phosphate cycle or C3 cycle is a series of biochemical redox reactions that take place in the stroma of chloroplast in photosynthetic organisms.

The cycle was discovered by Melvin Calvin, James Bassham, and Andrew Benson at the University of California, Berkeley[3] by using the radioactive isotope carbon-14.

Photosynthesis occurs in two stages in a cell. In the first stage, light-dependent reactions capture the energy of light and use it to make the energy-storage and transport molecules ATP and NADPH. The Calvin cycle uses the energy from short-lived electronically excited carriers to convert carbon dioxide and water into organic compounds[4] that can be used by the organism (and by animals that feed on it). This set of reactions is also called carbon fixation. The key enzyme of the cycle is called RuBisCO. In the following biochemical equations, the chemical species (phosphates and carboxylic acids) exist in equilibria among their various ionized states as governed by the pH.

The enzymes in the Calvin cycle are functionally equivalent to most enzymes used in other metabolic pathways such as gluconeogenesis and the pentose phosphate pathway, but they are found in the chloroplast stroma instead of the cell cytosol, separating the reactions. They are activated in the light (which is why the name "dark reaction" is misleading), and also by products of the light-dependent reaction. These regulatory functions prevent the Calvin cycle from being respired to carbon dioxide. Energy (in the form of ATP) would be wasted in carrying out these reactions that have no net productivity.

The sum of reactions in the Calvin cycle is the following:

3 CO 2 + 6 NADPH + 6 H+ + 9 ATP → glyceraldehyde-3-phosphate (G3P) + 6 NADP+ + 9 ADP + 3 H 2O + 8 Pi (Pi = inorganic phosphate) Hexose (six-carbon) sugars are not a product of the Calvin cycle. Although many texts list a product of photosynthesis as C 6H 12O 6, this is mainly a convenience to counter the equation of respiration, where six-carbon sugars are oxidized in mitochondria. The carbohydrate products of the Calvin cycle are three-carbon sugar phosphate molecules, or "triose phosphates", namely, glyceraldehyde-3-phosphate (G3P).

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105898view11:36, 16 August 2019MkutmonHMDB identifier normalization
97813view14:31, 9 June 2018EgonwUndo revision 97771 by [[Special:Contributions/Youssefwalid|Youssefwalid]] ([[User talk:Youssefwalid|Talk]]) Text cannot be copied from other websites.
97771view13:34, 7 June 2018YoussefwalidModified description
78379view10:22, 7 January 2015MaintBotadded missing graphIds
76143view15:53, 11 June 2014SbohlerAll protein nodes are now annotated with Uniprot-TrEMBL IDs. Some nodes were split up into their different isoforms/subunits.
75326view13:38, 19 May 2014SbohlerAdded cell border and label for Chloroplast.
73916view09:45, 4 March 2014AnweshaAdded pathway identifiers
73915view09:42, 4 March 2014AnweshaAdded metabolite identifiers
73881view21:54, 26 February 2014MaintBotOntology Term : 'photosynthesis pathway' added !
73880view21:52, 26 February 2014MaintBotfixing scaling issue
73603view13:21, 4 February 2014AnweshaNew pathway

External references


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NameTypeDatabase referenceComment
2H+MetaboliteCHEBI:18276 (ChEBI)
3-phosphoglycerateMetaboliteC00197 (KEGG Compound)
ATPMetaboliteHMDB00538 (HMDB)
CO2 + H2OMetabolite
CO2MetaboliteHMDB01967 (HMDB)
Dihydroxyacetone phosphateMetaboliteHMDB01473 (HMDB)
GlycolysisPathwayWP2621 (WikiPathways)
H+MetaboliteCHEBI:15378 (ChEBI)
H2OMetaboliteHMDB02111 (HMDB)
NADP+MetaboliteHMDB00217 (HMDB)
NADPHMetaboliteHMDB00221 (HMDB)
RuBisCO LSUProteinO03042 (Uniprot-TrEMBL)
RuBisCO SSU1AProteinP10795 (Uniprot-TrEMBL)
RuBisCO SSU1BProteinP10796 (Uniprot-TrEMBL)
RuBisCO SSU2BProteinP10797 (Uniprot-TrEMBL)
RuBisCO SSU3BProteinP10798 (Uniprot-TrEMBL)
RuBisCO activaseProteinP10896 (Uniprot-TrEMBL)
Starch MetabolismPathwayWP2622 (WikiPathways)
aldolase 1ProteinO65581 (Uniprot-TrEMBL)
aldolase 2ProteinQ944G9 (Uniprot-TrEMBL)
carbonic anhydrase 1ProteinP27140 (Uniprot-TrEMBL)
carbonic anhydrase 2ProteinP42737 (Uniprot-TrEMBL)
erythrose 4-phosphateMetaboliteHMDB01321 (HMDB)
fructose 1,6-bisphosphateMetaboliteHMDB01058 (HMDB)
fructose 6-phosphateMetaboliteHMDB00124 (HMDB)
fructose-1,6-bisphosphataseProteinP25851 (Uniprot-TrEMBL)
fructose-1,6-bisphosphateMetaboliteHMDB01058 (HMDB)
glyceraldehyde-3-phosphate dehydrogenase 1ProteinP25856 (Uniprot-TrEMBL)
glyceraldehyde-3-phosphate dehydrogenase 2ProteinQ9LPW0 (Uniprot-TrEMBL)
phosphoglycerate kinase 1ProteinQ9LD57 (Uniprot-TrEMBL)
phosphoglycerate kinase 2ProteinP50318 (Uniprot-TrEMBL)
phosphoribulokinaseProteinP25697 (Uniprot-TrEMBL)
ribose 5-phosphateMetaboliteHMDB01548 (HMDB)
ribulose 5-phosphate 3-epimeraseProteinQ9SAU2 (Uniprot-TrEMBL)
ribulose 5-phosphate isomerase 3ProteinQ9S726 (Uniprot-TrEMBL)
ribulose 5-phosphate isomerase 4ProteinQ9FI13 (Uniprot-TrEMBL)
ribulose 5-phosphateMetaboliteHMDB00618 (HMDB)
sedoheptulose 1,7-bisphosphataseProteinP46283 (Uniprot-TrEMBL)
sedoheptulose 1,7-bisphosphateMetabolite
sedoheptulose 7-phosphateMetaboliteHMDB01068 (HMDB)
transketolase 1ProteinQ8RWV0 (Uniprot-TrEMBL)
transketolase 2ProteinF4IW47 (Uniprot-TrEMBL)
triose phosphate isomeraseProteinQ9SKP6 (Uniprot-TrEMBL)

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