The Calvin cycle is the process by which plants synthesize molecules from CO₂and water. The process is driven by high energy ATP and the reducing agent NADPH, produced by the light reaction.

The Calvin cycle is sometimes called the dark reaction, in analogy to thelight reaction. However, this name is misleading because the two reactions occur in parallel. The Calvin cycle does not need sunlight, but uses ATP and NADPH, which are only produced when the sun is shining.

As the name suggests, the process is a cyclic sequence of chemical reactions catalyzed by many different enzymes. The most prominent of them is RuBisCO, which is also the most abundant protein in the world. It enables the plants to fixate carbon dioxide.

As it is shown in the figure above, the Calvin cycle produces 3-phosphoglycerate, a three-carbon molecule that is then used as the precursor to glucose and other sugars in other metabolic routes. These sugars are used as an energy source for the cells and as building blocks for many other cellular components.

Photosynthesisis the basis of all life on earth. 100 % of the food you have ever eaten was synthesized with the energy obtained by photosynthesis.