Calvin cycle

The Calvin cycle is a sequence of enzyme-catalyzed reactions that fixes carbon dioxide into carbohydrate precursors, using ATP and NADPH produced by the light reactions.

Carbon fixation: The incorporation of inorganic carbon dioxide into organic molecules. The cycle is photosynthesis’s central route for converting atmospheric carbon into organic compounds.
Light-dependent reactions: Photosynthetic reactions that use light energy to produce ATP, NADPH, and oxygen. They supply the ATP and NADPH consumed by the Calvin cycle.
Melvin Calvin: An American chemist who mapped the sequence of carbon-fixation reactions in photosynthesis. His laboratory identified the cycle’s intermediates using radioactive carbon.
C4 carbon fixation: A photosynthetic adaptation that concentrates carbon dioxide near RuBisCO using four-carbon compounds. It limits photorespiration by delivering carbon dioxide to the Calvin cycle in specialized cells.
RuBisCO: An enzyme that catalyzes the addition of carbon dioxide to ribulose-1,5-bisphosphate. It performs the cycle’s carbon-entry reaction and can also react with oxygen.
Adenosine triphosphate: A nucleotide that transfers usable chemical energy in cells. The cycle spends ATP to phosphorylate intermediates and regenerate its carbon acceptor.
Andrew Benson: An American biochemist who helped identify intermediates in photosynthetic carbon fixation. His chromatographic work with Calvin’s team revealed labeled cycle products.
Crassulacean acid metabolism: A photosynthetic adaptation that stores carbon dioxide at night and releases it for daytime fixation. It separates carbon uptake from the Calvin cycle in time rather than space.
3-phosphoglycerate: A three-carbon organic acid formed when RuBisCO’s unstable product splits. It is the first stable product of carbon fixation in the cycle.
Nicotinamide adenine dinucleotide phosphate: A coenzyme that carries electrons in its oxidized and reduced forms, NADP+ and NADPH. Its reduced form supplies electrons for reducing cycle intermediates.

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