Light-independent reaction

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Overview of the Calvin cycle and carbon fixation

In photosynthesis, the light-independent reactions, also somewhat misleadingly called the dark reactions (they don't require darkness, but they do require the products of the light reactions), are chemical reactions that convert carbon dioxide and other compounds into glucose. It occurs in the stroma, the fluid filled area of a chloroplast outside of the thylakoid membranes. These reactions, unlike the light-dependent reactions, do not need light to occur; hence the term dark reactions. These reactions take the products of the light-dependent reactions and perform further chemical processes on them. There are two light-independent reactions: carbon fixation and the Calvin-Benson cycle.

However in CAM (Crassulacean acid metabolism) plants, carbon fixation actually does take place at night.

Carbon fixation

Main article: carbon fixation

The carbon fixation reaction is the first step of the light-independent reactions. Carbon from carbon dioxide is "fixed" into a larger carbohydrate. Three pathways to occur: C3 carbon fixation (the most common), C4 carbon fixation, and CAM (Crassulacean Acid Metabolism). C3 fixation occurs as the first step of the Calvin-Benson cycle in all plants. C4 plants first fix carbon dioxide into malate, which is then used to supply carbon dioxide in the middle of the night to the Calvin-Benson cycle. CAM plants perform a similar process.

Calvin cycle

The Calvin-Benson cycle takes carbon dioxide and converts it to glucose, which the plant uses for energy.

External links

de:Dunkelreaktion



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