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Carbon fixation
From Wikipedia, the free encyclopedia
Carbon fixation is a process found in autotrophs, usually driven by photosynthesis, whereby carbon dioxide is converted into organic compounds. == Carbon fixation can also be carried out by the process of calcification in marine, calcifying organisms such as Emiliania huxleyi. In plants, there are three types of carbon fixation during photosynthesis:
- C3 - plant that uses the Calvin Cycle for the initial steps that incorporate CO2 into organic matter, forming a 3-carbon compound as the 1st stable intermediate. Most broadleaf plants and plants in the temperate zones are C3.
- C4 - plant that prefaces the Calvin Cycle with reactions that incorporate CO2 into 4-carbon compound. C4 plants have a distinctive leaf anatomy. This pathway is found mostly in hot regions with intense sunlight. Tropical grasses, such as sugar cane and maize are C4 plants, but there are many broadleaf plants that are C4.
- CAM - plant that uses Crassulacean acid metabolism as an adaptation for arid conditions. CO2 entering the stomata during the night is converted into organic acids, which release CO2 for the Calvin Cycle during the day, when the stomate is closed. The jade plant (Crassula ovata) and Cactus species are typical of CAM plants.
- Reverse Krebs cycle (also known as the reverse tricarboxylic acid cycle. The reverse TCA cycle, or the reverse citric acid cycle). The reaction is basically the Citric acid cycle run in reverse.