C4 carbon fixation

(noun)

A form of photosynthesis in which plants concentrate CO2 spatially, with a RuBisCO reaction centre in a "bundle sheath cell" that is inundated with CO2

Related Terms

  • crassulacean acid metabolism
  • Crassulacean acid metabolism (CAM).
  • C4 Carbon Fixation

Examples of C4 carbon fixation in the following topics:

  • CAM and C4 Photosynthesis

    • In contrast to C4 metabolism, which physically separates the CO2 fixation to PEP from the Calvin cycle, CAM temporally separates these two processes.
    • Decarboxylation of malate during the day releases CO2 inside the leaves, thus allowing carbon fixation to 3-phosphoglycerate by RuBisCO.
    • Due to the inactivity required by the CAM mechanism, C4 carbon fixation has a greater efficiency in terms of PGA synthesis.
    • Plants that do not use PEP-carboxylase in carbon fixation are called C3 plants because the primary carboxylation reaction, catalyzed by RuBisCO, produces the three-carbon 3-phosphoglyceric acids directly in the Calvin-Benson cycle.
    • Over 90% of plants use C3 carbon fixation, compared to 3% that use C4 carbon fixation; however, the evolution of C4 in over 60 plant lineages makes it a striking example of convergent evolution.
  • Nitrogen Fixation: Root and Bacteria Interactions

    • The NH3 resulting from fixation can be transported into plant tissue and incorporated into amino acids, which are then made into plant proteins.
    • Soil bacteria, collectively called rhizobia, symbiotically interact with legume roots to form specialized structures called nodules in which nitrogen fixation takes place .
    • Through symbiotic nitrogen fixation, the plant benefits from using an endless source of nitrogen from the atmosphere.
    • As in any symbiosis, both organisms benefit from the interaction: the plant obtains ammonia and bacteria obtain carbon compounds generated through photosynthesis, as well as a protected niche in which to grow.
    • Abiotic nitrogen fixation has been omitted.
  • The Calvin Cycle

    • The Calvin cycle is organized into three basic stages: fixation, reduction, and regeneration.
    • The light-independent reactions of the Calvin cycle can be organized into three basic stages: fixation, reduction, and regeneration.
    • RuBP has five atoms of carbon, flanked by two phosphates.
    • This process is called carbon fixation because CO2 is "fixed" from an inorganic form into organic molecules.
    • Only one carbon dioxide molecule is incorporated at a time, so the cycle must be completed three times to produce a single three-carbon GA3P molecule, and six times to produce a six-carbon glucose molecule.
  • The Role of Prokaryotes in Ecosystems

    • Prokaryotes play vital roles in the movement of carbon dioxide and nitrogen in the carbon and nitrogen cycles.
    • Carbon is one of the most important macronutrients.
    • Although the largest carbon reservoir in terrestrial ecosystems is in rocks and sediments, that carbon is not readily available.
    • A large amount of available carbon is found in land plants, which are producers that use carbon dioxide from the air to synthesize carbon compounds.
    • Gaseous nitrogen is transformed, or "fixed," into more-readily available forms such as ammonia through the process of nitrogen fixation by natural means, especially by microorganisms (prokayotes) in the soil.
  • Covalent Bonds and Other Bonds and Interactions

    • Its biosynthesis involves breaking the triple bond of molecular nitrogen, or N2, followed by the formation of several carbon-nitrogen single and double bonds.
    • Covalent bonds are commonly found in carbon-based organic molecules, such as DNA and proteins.
    • The four bonds of methane are also considered to be nonpolar because the electronegativies of carbon and hydrogen are nearly identical.
    • Both water and carbon dioxide have polar covalent bonds, but carbon dioxide is linear, so the partial charges on the molecule cancel each other out.
    • Its biosynthesis involves the fixation of nitrogen to provide feedstocks that eventually produce the carbon-nitrogen bonds it contains.
  • Essential Nutrients for Plants

    • About half of the essential elements are considered macronutrients: carbon, hydrogen, oxygen, nitrogen, phosphorus, potassium, calcium, magnesium, and sulfur.
    • The first of these macronutrients, carbon (C), is required to form carbohydrates, proteins, nucleic acids, and many other compounds; it is, therefore, present in all macromolecules.
    • On average, the dry weight (excluding water) of a cell is 50 percent carbon, making it a key part of plant biomolecules.
    • Some plants use it for nitrogen fixation; thus, it may need to be added to some soils before seeding legumes.
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