Talk:Light-independent reactions

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Untitled[edit]

This page needs serious expansion. It's been 16+ years since I taught this material, so I would appreciate the job being done by someone current in the area. David Shear 19:23, 16 October 2005 (UTC)[reply]

Intermediate Steps[edit]

The information here is the same as the information in my textbook, i was wondering if knows the complete RuBP regeneration phase. There are at least 3 molecules not shown in the diagram. Id love to add the amazing diagram im looking at now but it has another 10000000 years left on anti-wikipedia time. I also know the enzyme rate, which i will be adding now.

Andy Benson or Adam Benson[edit]

Who is Andy Benson? I haven't been able to find any information on him anywhere on the internet. On the Calvin cycle page his name is given as Andy Benson and on the Melvin Calvin page his name is given as Adam Benson. The funny thing is that both names are used equally as often in the articles I was able to locate on the internet. Someone needs to resolve this because I am clueless . . . 20:39, October 21, 2005 (UTC)

Added Reference to Benson ARP 17:41, 1 December 2005 (UTC)[reply]

Calvin Cycle diagram[edit]

Hey I just made/added an overview of the calvin cycle for this page and the rubisco page, I was wondering what everybody thinks. I'm worried it's to complicated/busy, I am wondering if i should dumb it down (ie get rid of the molecule diagrams). Anything else to change, I really want it to be great. Adenosine | Talk 08:35, September 2, 2005 (UTC)

But I think the figure is excellent; outstanding — especially in its doubly-enlarged form. Good artwork, layout & color! Nice touch with the splash stars. Please keep the molecule diagrams. In my opinion, they're more important than enzyme names since they show what goes in and what comes out. I used to hand plastic models around the class when I taught biochemistry. David Shear 19:23, 16 October 2005 (UTC)[reply]

God Bless who ever wrote this article. You just saved my ass, because I have a textbook that's written for people who already have an excellent understanding of basic biology, not an intro student such as myself. This is a great break-down for me. Thanks! - Poisonouslizzie | Talk 16:40, November 10, 2005 (ETZ)

I think that the diagram is good but is perhaps too complicated for someone without a fair grasp of the subject beforehand. I know there are much simpler diagrams in text books that I have seen.

Nice artwork and all, but isn't the diagram incorrect? I'm pretty sure it's glyceraldehyde-3-phosphate that is used in the "central metabolic pathways", i.e. glycolysis? Not 3-phosphoglycerate that is shown.

Re: Andy Benson[edit]

I am an undergraduate student in the life sciences and my Biochemistry textbook (Pratt & Cornely, 2004) gives the name as Andrew Benson. I don't know if that helps clear any confusion...

Thank you, too, for the diagrammatic overview of the Calvin cycle. It is less complicated than the diagrams in my text and the molecular structures make the visual overview easier than deciphering the chemical/technical names.

69.154.111.168 04:19, 7 December 2005 (UTC)[reply]

carbon dioxide///PGAL///ribulose diphosphate[edit]

a quick question... or two... how would one describe the interaction of carbon dioxide in the calvin-benson cycle?

also, how can the interaction of PGAL and ribulose diphosphate in the formation of glucose be described?

im a student at nassau community college, and i have a test in my Bio109 class tomorrow... and im having a little trouble clearly answering these questions.

please help me out if you can! thank you. [[User:69.123.155.24|69.123.155.24](UTC)Joyce


misleading....[edit]

six carbon sugars are not oxidized in the mitochondria... pyruvate is. someone should change that statement because it gives the wrong impression —The preceding unsigned comment was added by Acid.runner (talk • contribs) 23:35, 27 April 2007 (UTC).[reply]

Someones has been messing around with this page. In paragraph 1, someone has written that "Skiddy" helped discover this pathway. —Preceding unsigned comment added by 70.71.250.83 (talk) 04:51, 1 October 2007 (UTC)[reply]

It's been fixed. -- Gogo Dodo 04:55, 1 October 2007 (UTC)[reply]


somebody screws up this page[edit]

"Although many texts list a product of photosynthesis as C6H12O6, this is mainly a convenience to counter the equations PWnd newb PWnd newb PWnd newb PWnd newb PWnd newb PWnd newb PWnd newb PWnd newb PWnd newb PWnd newb PWnd newb PWnd newb PWnd newb PWnd newb PWnd newb PWnd newb of respiration," I guess thats not correct..

I also suppose that "(How PWnd newb PWnd newb PWnd newb PWnd newb PWnd newb PWnd newb PWnd newb PWnd newb PWnd newb ever, note that two PGAs are produced for every CO2 that enters the cycle, so this step utilizes 2ATP per CO2 fixed." isnt correct either.

same with "and the NADPH itself was oxidized and h PWnd newb PWnd newb PWnd newb PWnd newb PWnd newb PWnd newb PWnd newb PWnd newb PWnd newb encv PWnd newb PWnd newb PWnd newb PWnd newb PWnd newb e becomes NADP+. Again, two NADPH are utilized per CO2 fixed." and "E4P and a DH PWnd newb PWnd newb PWnd newb PWnd newb PWnd newb PWnd newb PWnd newb PWnd newb AP are converted into sedoheptulose-1,7-bisphosphate (7C) by transaldolase enzyme."

isnt it possible to ban his/her IP?

unfortunately, I dont know enough about the topic to reform the sentences..

SCyh 20:02, 18 December 2007 (GMT+1)

Calvin Cycle and Krebs Cycle[edit]

How are the Calvin Cycle and Krebs Cycle related? The Krebs Cycle was placed in "Calvin Cycle"'s See Also. Calvin cycle deals with photosynthesis in the stroma of the [chloroplast]]. However, the Krebs Cycle deals with celluar respiration in the matrix of the mitochondria. The only relation is the word "cycle", but the processes deal with two separate things. The name (and similarity) confuses students. Bdodo1992 (talk) 01:21, 15 January 2008 (UTC)[reply]

carbon balance in overview[edit]

The second carbon balance listed in the overview doesn't conserve carbons as far as I can tell.

3 CO2 + 6 C21H29N7O17P3 + 5 H2O + 9 C10H16N5O13P3 → C3H5O3-PO32- + 2 H+ + 6 NADP+ + 9 C10H15N5O10P2 + 8 Pi

Also it's a very weird equation to have in there... as it really provides no context for why you would write it that way. --72.85.232.202 (talk) 00:13, 25 June 2008 (UTC)[reply]

  • Nevermind, I see. It's just expanded out NADPH... that's somewhat silly, as NADP+ is not expanded out. I think the equation is just confusing really, and doesn't add much, as people can just click through if they are interested in seeing the cofactors. --72.85.232.202 (talk) 00:15, 25 June 2008 (UTC)[reply]
I've now commented out this equation; as noted above unless NADP+ is expanded it doesn't make sense. Peter coxhead (talk) 13:03, 28 February 2012 (UTC)[reply]

Sith reaction?[edit]

"The light-independent Calvin cycle, also (misleadingly) known as the "sith reaction" or "dark stage," "...

"Sith reaction"? Really? Never heard that before, nor can I find any references on the net.

ertdredge 13:39, 25 April 2009 (GMT+5)

Fong papers[edit]

Hi all,

Prof. Francis K. Fong tried to insert this edit and it was reverted for obvious reasons; he's engaged in discussion at User talk:DVdm and there is an ANI thread about it.

Could someone familiar with the subject matter please look at the diff and put any appropriate material from it into the article? Some Google searching does show that Prof. Fong did significant work in this area in the 1980's before getting into a dispute with Purdue at about that time, but I don't know anything more about it.

Thanks,

67.122.209.190 (talk) 14:10, 4 January 2011 (UTC)[reply]

Under a heading "Diversions and dead-ends", Portis and Parry, Discoveries in Rubisco (Ribulose 1,5-bisphosphate carboxylase/oxygenase): a historical perspective say that "A non-cyclic pathway for carbon fixation is proposed by Fong and Butcher (1988)". Not a ringing endorsement of Fong's argument. Fences&Windows 03:12, 5 January 2011 (UTC)[reply]
Hmm, I guess it's ok to mention it as an alternate view but not devote a lot of space to it. What about the other Calvin et al papers that Fong's diff cited? Are they mentioned? I don't have easy access to the Portis and Perry survey and I wouldn't understand it anyway. 67.122.209.190 (talk) 07:00, 5 January 2011 (UTC)[reply]
It shouldn't be mentioned, it was barely cited. Fong's insistence on this matter is something he should resolve off Wikipedia. We are not here to right great wrongs. If you can find someone other than Fong who supports his work, I'd like to see it as I didn't find any sources. Fences&Windows 23:22, 5 January 2011 (UTC)[reply]
I thought you did find a source, the historical survey mentioned, which itself is apparently fairly widely cited. I would have thought that if a historical survey of the topic cited Fong and Butcher's paper, that established enough notability to warrant a cite in Wikipedia (maybe along with other papers that it mentions, to not create undue weight). It occurs to me though, I'm clueless about the topic to the point of not knowing whether the cite (if we add one) should go into some other article rather than this one. Do you have access to Science Citations Index? Does it mention the Fong paper? 67.122.209.190 (talk) 03:08, 6 January 2011 (UTC)[reply]
  • I linked to the Portis and Perry survey. Adding the Fong/Butcher paper without undue weight would require a big expansion of the article which is way outside my capabilities. Nice job to Fences & Windows finding the pdf; I only saw that there was a paywall version. People looking at the pdf can find their way to the references that it points to, so this seems good enough for now. 67.122.209.190 (talk) 05:01, 6 January 2011 (UTC)[reply]

New diagrams[edit]

I've added some new "simple" diagrams to try to give a better intuitive understanding of the complex steps of the Calvin cycle, and also expanded the text a bit. Comments and reactions welcome. Peter coxhead (talk) 13:06, 28 February 2012 (UTC)[reply]

Alternative description[edit]

I removed the following passage from the article. It does have merits, but also some obvious shortcomings. Maybe it can serve as inspiration to improvements to the article. --Ettrig (talk) 10:04, 7 May 2012 (UTC)[reply] 

                           Calvin Cycle (or) C3 Cycle
  Light independent reactions take place in the stroma of the chloroplast.
  The ATP and NADPH synthesized during light phase utilized in the reduction of CO2
  to carbohydrates in the light independent phase (Dark Phase).
  Light independent phase is the major phase of photosynthesis, in this a series of bio-
  chemical reactions take place, each mediated by a specific enzyme.
  The heart of light independent reactions is the Calvin cycle, during which CO2 is fixed
  and converted into carbohydrates.
  Light independent phase does not directly depend on light, but it is dependent on the
  products of light reaction (ATP & NADPH).
  Based on the first stable compound obtained in the dark phase, CO2 fixations in plants
  are classified into C3 cycle (Calvin cycle) and C4 cycle (Hatch & Slack cycle).
  C3 cycle:
      Melvin Calvin and his coworkers discovered the sugar producing reactions involve
      nearly two dozen enzymes in a series of steps.
      Calvin & co., used the radioactive isotype 14C to study the carbon fixation (dark
      phase) in algae, led to discover the first stable compound in CO2 fixation i.e., a 3
      carbon containing molecule 3-Phospho Glyceric Acid (3-PGA). Hence, the dark
      phase came to be called C3 cycle (or) Calvin Cycle.
      The Calvin cycle is also called Photosynthetic Carbon Reduction (PCR) cycle (or)
      Reductive Pentose Phosphate (RPP) cycle.
      The Calvin cycle can be divided into three steps,
           1. Corboxylation.
           2. Reduction.
           3. Regeneration of RuBP.

1. Corboxylation: 

      It is the most crucial step in Calvin cycle. In this step, CO2 is fixed into two stable
      (3C) sugar molecules (3-PGA).
      The primary CO2 acceptor molecule in the green plants is RuBP, a 5C pentose
      sugar. RuBP refers to Ribulose 1,5-bis Phosphate.
      In this step, CO2 first combines with RuBP (5C) to form a 6 Carbon containing
      intermediate molecule that is immedieately splits into two 3C containing first stable
      sugar molecules called 3-PGA.
      This reaction takes place in the presence of enzyme RUBISCO. It refers to RuBP
      Carboxylase/Oxygenase. It is the abundant (25 to 50%) soluble protein in the leaves
      of green plants.
      During the formation of one glucose molecule, 6 CO2 molecules fixed by six (5C)
      RuBP and form total twelve 3-PGA.

2. Reduction: 

      The twelve 3-PGA undergoes reduction with the help of the assimilatory power to
      form twelve Phospho Glyceraldehyde (PGAL) molecules. Total 12 NADPH2 and 12
      ATP molecules utilized in this reduction.
      NADPH2 provides the hydrogen and ATP supplies energy for the reduction.
      The enzyme Glyceraldehyde 3-Phosphate dehydrogenase catalyzes this reaction.
      Among these twelve 3-PGA, two are transported into the cytoplasm and involved in
      the formation of one hexose (glucose) molecule.
      The hexose sugars may further be converted to sucrose or to starch and stored in
      storage cells.

3. Regeneration of RuBP: 

     The 5C RuBP is constantly required for the fixation of CO2 in the Calvin cycle. It is
     regenerated through another chain of reactions.
     Ten of the twelve Glyceraldehyde 3-Phosphate molecules are restructed using
     another 6 ATP and become six (5C) RuBP.
     Out of the five 3-PGA molecules, two are isomerised into Dihydroxy Acetone
     Phosphate (DHAP). The reaction is catalyzed by Triose Phosphate Isomerase.
     One G-3-P condenses with DHAP to form Fructose 1,6-Bis Phosphate. This reaction
     is catalysed by aldolase.
     Fructose 1,6-bis Phosphate undergoes dephosphorylation to form Fructose 6-
     Phosphate. This reaction is catalysed by fructose 1,6-bis phosphatase.
     Fructose 6-Phosphate combines with one molecule of G-3-P to form one molecule of
     (4C) Erythrose 4-Phosphate and one molecule of (5C) Xylulose 5-Phosphate. This
     reaction is catalysed by transketolase.
     (4C) Erythrose 4-Phosphate condenses with one DHAP(3C) and forms (7C) Sedo
     Heptulose 1,7-bis phosphate, in the presence of aldolase.
     (7C) Sedo Heptulose 1,7-bis phosphate removes one inorganic phosphate (iP) and
     forms the (7C) Sedo Heptulose 7-phosphate, in the presence of phosphatase.
     (7C) Sedo Heptulose 7-phosphate combines with G-3-P to form one molecule of
     (5C) Ribose 5-Phosphate and one molecule of (5C) Xylulose 5-phosphate, in the
     presence of transketolase.
     Two molecules of xylulose 5-phosphate are converted into two molecules of
     Ribulose 5-Phosphate, in the presence of epimerase.
     One molecule of Ribose 5-Phosphate is isomerized into Ribulose 5-Phosphate, in
     the presence of isomerase.
     The three molecules of Ribulose 5-Phosphate undergoes phosphorylation and form
     the three (5C) Ribulose 1,5-Bis Phosphate (RuBP), in the presence of kinase. 3 ATP
     molecules utilized in this reaction.
  For every CO2 molecule entering in the Calvin cycle, 3 ATP and 2 NADPH2 are
  required.
  To make one molecule of Glucose 6 turns of the cycle are required i.e., 18 molecules of
  ATP and 12 NADPH2 are needed.

Move discussion in progress[edit]

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