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Calvin Cycle
This is a diagram of the Calvin Cycle.

This is a diagram of the Calvin Cycle, which is the set of chemical reactions that occur without light (dark reactions) in photosynthesis. Atoms are black - carbon, white - hydrogen, red - oxygen, pink - phosphorus.

Mike Jones, Creative Commons License
The Calvin cycle is a set of redox reactions that occur without light during photosynthesis and carbon fixation. Here is a look at the redox reactions that occur during the Calvin cycle.

Other Names for the Calvin Cycle

You may know the Calvin cycle by another name. The set of reactions also are known as the dark reactions, C3 cycle, Calvin-Benson-Bassham (CBB) cycle, or reductive pentose phosphate cycle. The cycle was discovered in 1950 by Melvin Calvin, James Bassham, and Andrew Benson at the University of California, Berkeley. They radioactive carbon-14 to trace the path of carbon atoms in carbon fixation.

Overview of the Calvin Cycle

The Calvin cycle is part of photosynthesis, which occurs in two stages. In the first state, chemical reactions use energy from light to produce ATP and NADPH. In the second stage (Calvin cycle or dark reactions), carbon dioxide and water are converted into organic molecules, such as glucose. Although the Calvin cycle may be called the "dark reactions," these reactions don't actually occur in the dark or during nighttime. The reactions require reduced NADP, which comes from a light-dependent reaction. The Calvin cycle consists of:
  • carbon fixation
  • reduction reactions
  • ribulose 1,5-bisphosphate (RuBP) regeneration

Calvin Cycle Chemical Equation

The overall chemical equation for the Calvin cycle is:

3 CO2 + 6 NADPH + 5 H2O + 9 ATP → glyceraldehyde-3-phosphate (G3P) + 2 H+ + 6 NADP+ + 9 ADP + 8 Pi (Pi = inorganic phosphate)


Bassham J, Benson A, Calvin M (1950). "The path of carbon in photosynthesis". J Biol Chem 185 (2): 781–7. PMID 14774424.

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