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Effects of CO2 on the Calvin Cycle

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Effects of CO2 on the Calvin Cycle

Postby Dr.Watts » Mon Oct 15, 2007 2:36 am

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Last edited by Dr.Watts on Tue Oct 16, 2007 11:32 pm, edited 1 time in total.
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Postby blcr11 » Mon Oct 15, 2007 7:12 am

Once CO2 is removed, RuDP can no longer be converted to PGA. PGA levels fall, then, because it can no longer be replenished via the cycle. But whatever PGA has already entered the cycle can still proceed--that is, until it gets to RuDP, which now cannot be used to make more PGA. So RuDP accumulates as the levels back up behind the block in CO2 fixation/PGA production. This is also kind of an object lesson in general metabolism. In the absence of any other utilization pathway, if a step is blocked along the pathway, substrate levels behind the block accumulate, while products beyond the block fall.
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Postby mith » Mon Oct 15, 2007 2:51 pm

RuBp isn't increasing, it's RuDp according to your graph
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Postby xRadio » Mon Oct 15, 2007 3:08 pm

mith wrote:RuBp isn't increasing, it's RuDp according to your graph


its the same thing
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Postby mith » Mon Oct 15, 2007 4:02 pm

bisphosphate Vs diphosphate?
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Postby xRadio » Mon Oct 15, 2007 8:03 pm

mith wrote:bisphosphate Vs diphosphate?


I dont think it matters in this situation, and the question states its RuBP. Therefore I own you.
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Postby Dr.Watts » Mon Oct 15, 2007 8:22 pm

blcr11 wrote:Once CO2 is removed, RuDP can no longer be converted to PGA. PGA levels fall, then, because it can no longer be replenished via the cycle. But whatever PGA has already entered the cycle can still proceed--that is, until it gets to RuDP, which now cannot be used to make more PGA. So RuDP accumulates as the levels back up behind the block in CO2 fixation/PGA production. This is also kind of an object lesson in general metabolism. In the absence of any other utilization pathway, if a step is blocked along the pathway, substrate levels behind the block accumulate, while products beyond the block fall.


ooh thats perfect.. i didnt realize that the accumulated PGA would go on in the cycle :D

thanks alot!
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Postby mith » Mon Oct 15, 2007 9:39 pm

<---owned :(
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Postby xRadio » Tue Oct 16, 2007 9:59 pm

What kind of plant would this occur in? C3, C4, or CAM?
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Postby MrMistery » Wed Oct 17, 2007 9:02 am

well you would need at least two graphs to compare, but i would say that in C3. cause C4 plants have PEP carboxylase that has a higher aphinity for CO2(actually for HCO3-)
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Postby xRadio » Thu Oct 18, 2007 1:56 am

MrMistery wrote:well you would need at least two graphs to compare, but i would say that in C3. cause C4 plants have PEP carboxylase that has a higher aphinity for CO2(actually for HCO3-)


ahh yes yes of courseeeeeee
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