Talk:Biological carbon fixation

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Untitled

From the article: "The Calvin cycle in plants accounts for the preponderance of carbon fixation on land." What does that mean? Is the intended meaning that most of carbon fixed on land is fixed via the Calvin cycle in plants?

Are there any processes other that photosynthesis that fix carbon?

What about carbon fixation by marine animals and micro-organisms? There must be a lot of carbon locked permanently in chalk, limestone and marble. Is this process continuing, and if so, what proportion of anthropogenic carbon is being fixed in this way?

Carbon Fixation Processes

It would be helpful, I think, were all three of the Wikipedia articles on particular carbon fixation processes -- C3, C4 & CAM -- be placed together under this "Carbon Fixation" banner.

I think this is a much plant-related subject; many autotrophic microorganisms exist as well. Why not add the three other CO2 fixation routes (acetyl CoA, rTCA etc)?

Animal cells?

From Earl Evans (written by me): "This led to his demonstration that animal cells are capable of fixing carbon dioxide to synthesize carbohydrates, a work which earned him both the 1941 Lilly Prize, and in 1942, the chairmanship of the department."

Can anyone provide more information on this? DS (talk) 13:52, 14 August 2008 (UTC)

I've found a paper about it and have added a little info.Smartse (talk) 18:35, 26 April 2009 (UTC)

Reductionism

Life on Earth can be reduced to redox.

Oxygenic photosynthesis reduces carbon

2H₂O → 4e^- + 4H⁺ + O₂

CO₂ + 4e^- + 4H⁺ → CH₂O + H₂O

Aerobic respiration oxidizes carbon

CH₂O + H₂O → 4e^- + 4H⁺ + CO₂

O₂ + 4e^- + 4H⁺ → 2H₂O

Therefore, life on Earth is

CO₂ + H₂O ⇌ CH₂O + O₂

using solar energy made like this

4 ¹H⁺ → ⁴He²⁺ + 2e⁺

J G Campbell (talk) 01:41, 7 October 2011 (UTC)

Plants and algae made simple

Plants means land plants. Algae means all eukaryotes with plastids, except plants. Some algae are protists. Some algae have lost the ability to photosynthesize. Algae are polyphyletic. Plants are monophyletic, and are descended from an alga. Plastids are monophyletic, and are descended from a cyanobacterium through endosymbiosis. The monophyly of plastids requires secondary endosymbiosis, at least. J G Campbell (talk) 16:04, 30 March 2012 (UTC)

Red, green, and blue algae have primary plastids, descended from a cyanobacterium through the unique primary endosymbiotic event. All other algae have secondary or tertiary plastids, derived from red or green algae through secondary or tertiary endosymbiosis. Plants have primary plastids because plants are descended from a green alga. The group with primary plastids is monophyletic. Paulinella is a freak. J G Campbell (talk) 18:26, 30 March 2012 (UTC)

Oh yeah, the punch line, in bold. Life on Earth depends on cyanobacteria. J G Campbell (talk) 19:14, 30 March 2012 (UTC)

Glaucophytes are not usually called blue algae, but I couldn't resist. My dictionary gives bluish gray and bluish white as meanings of glaucous. J G Campbell (talk) 18:27, 1 April 2012 (UTC)

I've put references under Further reading. If you read just one, read Keeling 2010. J G Campbell (talk) 22:49, 10 April 2012 (UTC)

One more thing about cyanobacteria. It was the free oxygen produced by cyanobacteria that made eukaryotes possible in the first place. Cyanobacteria did change the world. Twice. J G Campbell (talk) 19:18, 15 April 2012 (UTC)

Calvin cycle

I have removed the recent contribution "Carbon fixation is part of a light independent process called the Calvin Cycle" from the lead paragraph. The Calvin cycle is only one of six known autotrophic carbon fixation pathways. Besides, in photosynthesis, the Calvin cycle is not light independent. It is both driven and regulated by light. No light, no Calvin cycle. At least, not for long. In the lead paragraph, I'd like to keep things simple by treating the Calvin cycle like the elephant in the room, and not mentioning it. It should be enough to mention photosynthesis. J G Campbell (talk) 17:07, 13 April 2012 (UTC)

"Light reaction" and "dark reaction" have fallen into disuse. J G Campbell (talk) 21:39, 14 April 2012 (UTC)

Photosynthesis

I want photosynthesis to mean photoautotrophic carbon fixation. This should include everything from photon absorption through production of triose or acetate or pyruvate. Unfortunately, I can't find anyone who will say anything so simple and obvious. J G Campbell (talk) 17:49, 15 April 2012 (UTC)

When the word photosynthesis was coined at the end of the nineteenth century, it did mean photoautotrophic carbon fixation, if not in those words. After a century of progress, it means some process vague enough to encompass photoautotrophic carbon fixation, while allowing every heterotroph with reaction centers to be called a photosynthetic organism. J G Campbell (talk) 19:12, 16 April 2012 (UTC)

Most electron flow in oxygenic photosynthesis is linear (noncyclic)

(2H₂O)_lumen → (4H⁺ + O₂)_lumen + 4e^-

or accounting for protons pumped across the thylakoid membrane into the thylakoid lumen, and for NADPH produced

(2H₂O)_lumen + 2NADP⁺ + 10H₂O → (12H⁺ + O₂)_lumen + 2NADPH + 10OH^-

J G Campbell (talk) 00:25, 25 April 2012 (UTC)

Major edits

I have been editing today and made a big cut on content. Because I might have erred, the cut content is left here in the event I messed up. Some of this material is redundant and some of it seems tangential (discussing the pigments) to the topic of CO2 fixation.--Smokefoot (talk) 20:46, 9 March 2013 (UTC)

==Anoxygenic photosynthesis== [[Purple bacteria]], green sulfur bacteria, and green nonsulfur bacteria are ''an''oxygenic photosynthetic organisms containing the pigment [[bacteriochlorophyll]]. The [[purple bacteria]] use the Calvin cycle. The [[green sulfur bacteria]] use the reductive citric acid cycle. The [[Chloroflexi (phylum)|green nonsulfur bacteria]] use the 3-hydroxypropionate cycle. [[Phototroph]]s are organisms which convert sunlight to metabolic energy. Phototrophy is known in [[eukaryotes]], across six [[Phylum|phyla]] of bacteria, and in [[Archaea]]. However, phototrophy does not necessarily imply autotrophic carbon fixation. In recent decades, a great many phototrophic bacteria and archaea, which lack autotrophic carbon fixation pathways, have been discovered. They are [[obligate]]ly heterotrophic phototrophs, not photoautotrophs. Whether obligately heterotrophic phototrophy should be called photosynthesis is a matter of opinion. ===Rhodopsin phototrophs=== In the early 1970s, the simplest phototrophic mechanism now known, was discovered in some obligately heterotrophic [[archaea]] of the [[Halobacteriales]]. The cell membrane of these organisms is spanned by molecules of the purple pigment [[bacteriorhodopsin]], a protein that binds [[retinal]]. When light activates the retinal, the protein pumps protons across the membrane, and the organism makes ATP using the [[proton gradient]] generated.<ref name="Oesterhelt73"> {{cite journal |author=Oesterhelt D, Stoeckenius W |year=1973 |title=Functions of a new photoreceptor membrane |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=70 |issue=10 |pages=2853–7 |pmid=4517939 |pmc=427124 |doi=10.1073/pnas.70.10.2853|bibcode = 1973PNAS...70.2853O }} </ref><ref name="Danon74"> {{cite journal |author=Danon A, Stoeckenius W |year=1974 |title=Photophosphorylation in ''Halobacterium halobium'' |journal=Proc. Natl. Acad. Sci. U.S.A. |volume=71 |issue=4 |pages=1234–8 |pmid=4524635 |pmc=388199 |doi=10.1073/pnas.71.4.1234|bibcode = 1974PNAS...71.1234D }} </ref> Some uncultured marine proteobacteria also have the genes needed to produce retinal and bacteriorhodopsin, and are presumably phototrophic.<ref name="Béjà00"> {{cite journal |author=Béjà O, Aravind L, Koonin EV, Suzuki MT, Hadd A, Nguyen LP, Jovanovich SB, Gates CM, Feldman RA, Spudich JL, Spudich EN, DeLong EF |year=2000 |title=Bacterial rhodopsin: evidence for a new type of phototrophy in the sea |journal=Science |volume=289 |issue=1902-6 |pages=1902–6 |doi=10.1126/science.289.5486.1902 |pmid=10988064|bibcode = 2000Sci...289.1902B }} </ref><ref name="Venter04"> {{cite journal |author=Venter JC, et al. |year=2004 |title=Environmental genome shotgun sequencing of the Sargasso Sea |journal=Science |volume=304 |issue=5667 |pages=66–74 |doi=10.1126/science.1093857 |pmid=15001713|bibcode = 2004Sci...304...66V }} </ref> These organisms produce metabolic energy by photophosphorylation, but do not fix carbon autotrophically. ===Heliobacteria=== In the 1980s, the aerobic anoxygenic phototrophic bacterium [[heliobacteria]], of the [[Firmicutes]], was discovered. They retain bacteriochlorophyll and a rudimentary version of the type I reaction center found in the green sulfur bacteria. The heliobacteria are obligately heterotrophic, and another example of phototrophs that do not fix carbon autotrophically.

Respiration in the evenings

Related to fixed carbon, the article says: "40% is consumed by respiration in the evenings following each day of photosynthesis". Respiration takes place in the morning, in the afternoon, in the evening and at night. --Miguelferig (talk) 18:35, 30 June 2014 (UTC)

Ok. That text you quoted does not actually say that it does not: it only says that 40% of fixed carbon is consumed in the evening. Does the article state how much in total is consumed by the plant? Firejuggler86 (talk) 11:47, 27 November 2020 (UTC)

carbon isotope discrimmination

In this section it mentions rubisco preferentially binding to carbon-12 but then goes on to say C12:C13 is lower in the plant than in air, should it not be the other way round? — Preceding unsigned comment added by Jammacus (talk • contribs) 17:16, 25 March 2015 (UTC)

Assessment comment

The comment(s) below were originally left at Talk:Biological carbon fixation/Comments, and are posted here for posterity. Following several discussions in past years, these subpages are now deprecated. The comments may be irrelevant or outdated; if so, please feel free to remove this section.

Rated "top" as high school/SAT biology content and because of media coverage and public interest in the climate change debate. - tameeria 23:25, 18 February 2007 (UTC)

Last edited at 23:25, 18 February 2007 (UTC). Substituted at 10:52, 29 April 2016 (UTC)

Net vs Gross makes no sense

I can't figure out the original meaning from the edits, but the "net vs gross" section does not talk about net vs gross. Instead it just sums up the various sources. — Preceding unsigned comment added by 216.185.73.133 (talk) 15:27, 21 June 2018 (UTC)

Alternative pathways to Calvin-Benson

Hello, me and my group have to edit the alternative pathways to Calvin-Benson cycle, the question is: in this section (Carbon Fixation) have we to put all the information on the alternative pathways or just an introduction and then go to the page of the alternative cycle and put things there? Thank u all. — Preceding unsigned comment added by Gabrieledef96 (talk • contribs) 15:56, 28 November 2019 (UTC)

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Ecological Significance and Human Impact

The article provides a valuable overview of biological carbon fixation, highlighting its importance in photosynthesis and chemosynthesis for organic matter production. However, I believe it would be beneficial to delve deeper into two key aspects.

- Firstly, it is essential to emphasize the ecological relevance of primary production as the foundation of terrestrial and aquatic processes. Biological carbon fixation triggers the production of organic matter by plants and other photosynthetic organisms, establishing the basis for food chains and maintaining gas balance in the atmosphere by absorbing CO2 and releasing oxygen. This interaction is crucial for the health and stability of ecosystems. - Secondly, addressing the human impact on this process is crucial. Human activities such as fossil fuel combustion and deforestation are drastically altering the carbon cycle, increasing the concentration of CO2 in the atmosphere and contributing to global warming and climate change. Understanding biological carbon fixation and its implications is vital to address these environmental challenges and promote sustainable practices that protect our ecosystems and the global climate. - Comment added by: User:Floralepe Floralepe (talk) 23:54, 24 March 2024 (UTC)