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.

Overview of C4 carbon fixation:

1.C4 plants first fix carbon dioxide into malate:

2. Malate is then used to supply carbon dioxide in the middle of the night to the Calvin-Benson cycle:

3. Phosphoenol pyruvate (PEP) is then recovered from Pyruvate:

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