<P> Six autotrophic carbon fixation pathways are known as of 2011 . The Calvin cycle fixes carbon in the chloroplasts of plants and algae, and in the cyanobacteria . It also fixes carbon in the anoxygenic photosynthetic proteobacteria called purple bacteria, and in some non-phototrophic proteobacteria . </P> <P> In photosynthesis, energy from sunlight drives the carbon fixation pathway . Oxygenic photosynthesis is used by the primary producers--plants, algae, and cyanobacteria . They contain the pigment chlorophyll, and use the Calvin cycle to fix carbon autotrophically . The process works like this: </P> <Dl> <Dd> 2H O → 4e + 4H + O </Dd> </Dl> <Dd> 2H O → 4e + 4H + O </Dd>

Fixation of carbon dioxide in the calvin cycle