Carbon dioxide assimilation
| Parent |
| Metabolic pathway |
| Subordinate |
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CAM C 4 Calvin cycle (C 3 ) Red. TCA Red. Acetyl-CoA path 3-hydroxypropionate cycle |
| Gene Ontology |
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| QuickGO |
With carbon dioxide assimilation ( lat. Assimulatio "similarity") one describes the absorption of carbon and oxygen from carbon dioxide (CO 2 ) in living beings to build up organic , endogenous carbon compounds. The first step in this is the formation of a carboxy group . Since carbon dioxide is bound in the organic substances, it is also called carbon dioxide fixation .
A distinction is made between autotrophic and heterotrophic carbon dioxide assimilation. In autotrophic organisms, carbon dioxide is the only source of carbon for building up the body's own building materials. By contrast, heterotrophic organisms mainly use organic carbon compounds as a source of building materials and only assimilate carbon dioxide to a small extent.
Since life on earth is based on the chemical diversity of carbon compounds, i. H. All living beings need carbon for their cell components and their metabolism , the ability of autotrophs, namely plants , algae , many bacteria and archaea , to synthesize organic carbon compounds exclusively from inorganic substances, is the prerequisite for the existence of heterotrophic forms of life that rely on the availability of organic substances are dependent.
There are several ways in which carbon dioxide is assimilated. With autotrophs the following ways occur:
- Calvin cycle (alternative names: Calvin-Benson-Bassham cycle, reductive pentose phosphate cycle , dark reaction of photosynthesis )
- Reductive citric acid cycle (alternative name: Arnon-Buchanan cycle)
- Reductive acetyl-CoA route (alternative names: Wood-Ljungdahl route, CO dehydrogenase / acetyl-CoA synthase route)
- 3-hydroxypropionate cycle (alternative name: 3-hydroxypropionate / malyl-CoA cycle)
- 3-hydroxypropionate / 4-hydroxybutyrate cycle
- Dicarboxylate / 4-hydroxybutyrate cycle
- ( Serinweg )
- ( Ethylmalonyl CoA route )
While plants and cyanobacteria only use the Calvin cycle , the other paths are found with different representatives in the realms of bacteria and archaea , which are thereby able to grow with carbon dioxide as the only carbon source ( autotrophic ).
In heterotrophs, carbon dioxide is introduced into the metabolism in some anaplerotic reactions , for example in the formation of oxaloacetate from pyruvate and carbon dioxide.
literature
- Berg, IA. et al . (2010): Autotrophic carbon fixation in archaea . In: Nat Rev Microbiol . ; PMID 20453874 ; doi : 10.1038 / nrmicro2365