You can mark you interesting snippets of text that will be available through a unique link in your browser.


Carbon fixation

Carbon fixation

Carbon fixation is a process found in autotrophs (organisms that produce their own food), usually driven by photosynthesis, whereby carbon dioxide is changed into organic materials. Carbon fixation can also be carried out by the process of calcification in marine, calcifying organisms such as "Emiliania huxleyi".

The Calvin Cycle is the most common method of carbon fixation.

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.

In addition to the Calvin cycle, the following alternative pathways are currently known to be used in certain autotrophic microorganisms:
* 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 and is used by photolithoautotrophic eubacteria of the Chlorobiales and some chemolithoautotrophic sulfate-reducing bacteria.
* Reductive acetyl CoA Pathway is found in methanogenic archaebacteria and in acetogenic and some sulfate-reducing eubacteria as a way of fixing carbon.
* 3-Hydroxypropionate Pathway is found in photolithoautotrophically grown eubacteria of the genus Chloroflexus and in modified form in some chemolithoautotrophically grown archaebacteria as a way of fixing carbon.


Wikimedia Foundation. 2010.

  
Share  

Look at other dictionaries:

  • carbon fixation — noun any process, such as photosynthesis, whereby atmospheric carbon dioxide is converted into organic compounds …   Wiktionary

  • C4 carbon fixation — is one of three biochemical mechanisms, along with C3 and CAM photosynthesis, used in carbon fixation. It is named for the 4 carbon molecule present in the first product of carbon fixation in these plants, in contrast to the 3 carbon molecule… …   Wikipedia

  • C3 carbon fixation — is a metabolic pathway for carbon fixation in photosynthesis. This process converts carbon dioxide and ribulose bisphosphate (RuBP, a 5 carbon sugar) into 3 phosphoglycerate through the following reaction::6 CO2 + 6 RuBP → 12 3… …   Wikipedia

  • Carbon dioxide — Carbon dioxide …   Wikipedia

  • Fixation — may refer to the following:In science: *Fixation (psychology), the state in which an individual becomes obsessed with an attachment to another human, an animal, or an inanimate object *Fixation (visual) maintaining the gaze in a constant… …   Wikipedia

  • Fixation Biologique De L'azote — La fixation biologique de l azote est un processus qui permet à un organisme de produire des substances protéiques à partir de l azote gazeux présent dans l atmosphère et l environnement. C est le processus de réduction enzymatique de N2 (azote… …   Wikipédia en Français

  • Fixation biologique de l'azote — La fixation biologique de l azote est un processus qui permet à un organisme de produire des substances protéiques à partir de l azote gazeux présent dans l atmosphère et l environnement. C est le processus de réduction enzymatique de N2 (azote… …   Wikipédia en Français

  • Carbon-13 — Infobox isotope alternate names = symbol =C mass number =13 mass = num neutrons =7 num protons =6 abundance =1.109% halflife = error halflife = background =#F99 text color = decay product = decay symbol = decay mass = decay mode1 = decay energy1 …   Wikipedia

  • Carbon-14 — Infobox isotope background = #999999 isotope name = Carbon 14 num neutrons = 8 num protons = 6 isotope filename = alternate names = radiocarbon mass number=14 abundance = 1 part per trillion symbol=C decay product = 14N halflife=5,730 error… …   Wikipedia

  • Fixation de l'azote — La fixation biologique de l azote est un processus qui permet à un organisme de produire des substances protéiques à partir de l azote gazeux présent dans l atmosphère et l environnement. C est le processus de réduction enzymatique de N2 (azote… …   Wikipédia en Français