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2. Research - if it has been said it will be on the internet. Ignorance is no longer a justifiable reason for buying the wrong thing. Take the time to research in detail everything that you could possible want to know about
3. Testimonials - don't know anybody that has bought a Calvin Cycle? Wrong! If the Calvin Cycle is good the internet will let you know. Use the Internet as a friend and get testimonials before you buy.
4. Questions - Got a question about Calvin Cycle then search the Forums, FAQ's, Blogs etc. Don't be afraid to ask .....
5. Reputation - Never heard of the company selling Calvin Cycle? Don't worry, no reason why you should know every company in the world, but you know someone that does! Use the internet to find out what people are saying about Calvin Cycle and build up a picture of their reputation for sales, returns, customer service, delivery etc.
6. Returns - still worried that even after all of the above your Calvin Cycle wont be what you want? Check out the returns policy. There is so much competition now that someone, somewhere is bound to offer the terms that you are comfortable with.
7. Feedback - happy with your Calvin Cycle then let people know, after all you are depending on others people input in your buying decision, so why not give a little back.
8. Security - check for the yellow padlock on the Calvin Cycle site before you buy, and the s after http:/ /i.e. https:// = a secure site
9. Contact - got a question about Calvin Cycle, or want to leave a comment then check out the sites contact page. Reputable companies have them and respond.
10. Payment - ready to pay for your Calvin Cycle, then use your credit card or PayPal! Be aware of companies that don't accept them, there may be genuine reasons but given the huge amount of choice you have when buying online there is no reason at all not to buy via credit card or PayPal.
The
Calvin cycle (or
Calvin-Benson cycle or carbon fixation) is a series of biochemistry reactions that takes place in the stroma of
chloroplasts in photosynthesis organisms. It was discovered by Melvin Calvin and Andrew Benson at the University of California, Berkeley with James Bassham also contributing. It is one of the light-independent reactions or dark reactions.
Steps of the Calvin cycle
- The enzyme RuBisCO catalyses the carboxylation of Ribulose-1,5-bisphosphate, a 5 carbon compound, by carbon dioxide (a total of 6 carbons). Rubisco is a large, slow enzyme averaging 3 substrate per second compared to 1000/s of most other enzyme in the Calvin cycle. Two molecules of glycerate 3-phosphate, a 3-carbon compound, are created. (also: 3-phosphoglycerate, 3-phosphoglyceric acid, 3PGA)
- The enzyme phosphoglycerate kinase catalyses the phosphorylation of 3PGA by ATP (which was produced in the light-dependent stage). 1,3-bisphosphoglycerate (glycerate-1,3-bisphosphate) and Adenosine diphosphate are the products. (However, note that two PGAs are produced for every CO2 that enters the cycle, so this step happens twice.)
- The enzyme G3P dehydrogenase catalyses the redox of 1,3BPGA by NADPH (which was another product of the light-dependent stage). Glyceraldehyde 3-phosphate (also G3P, GP) is produced, and the NADPH itself was oxidised and hence becomes NADP+.
(Simplified versions of the Calvin cycle integrate the remaining steps, except for the last one, into one general step - the regeneration of RuBP - also, one G3P would exit here.)
Up to this point, as per the overall equation given above, 6 carbon dioxide molecules would have been converted, with the use of 6 RuBP, 12 ATP and 12 NADPH, to 12 G3P molecules. One F6P, (= 2 G3P) then exits the cycle, while 10 of these G3P molecules continue, giving a ratio of 1:5 G3P. Obviously, the ratio of carbon dioxide entering the cycle to RuBP already present is also 1:5.
- F6P is then combined with another G3P (total 9C) and then cleaved into xylulose-5-phosphate (X5P) and erythrose-4-phosphate by transketolase.
- E4P and DHAP are converted into sedoheptulose-1,7-bisphosphate (7C) by a transaldolase enzyme.
- S7P is then combined with another G3P (total 10C) and then cleaved into another X5P and ribose-5-phosphate (R5P) again by transketolase.
- Finally, phosphoribulokinase phosphorylates RuP into RuBP, ribulose-1,5-bisphosphate, completing the Calvin cycle. This requires the input of one ATP.
All the G3P produced earlier is converted into RuBP (5C), so 10 G3Ps (30C, 10 phosphates) were needed to produce 6 RuBPs (30C, 6 phosphates). 6 ATPs were also needed in the last step, giving a total of 18 ATPs used up per 6 CO2s. However, four phosphate ions are lost and these also form ATP. The energy in those ATPs is used to drive some of the reactions.
At high temperatures, RuBisCO will react with O2 instead of CO2 in
photorespiration. This turns RuBP into 3PGA and 2-phosphoglycolate, a 2-carbon molecule which can be converted into 3PGA, some of which will exit the Calvin cycle. However, if this continues the RuBP will eventually be depleted, which slows down the cycle if electrons are entering from the light-dependent reaction too quickly.
The cycle has to be repeated for six times, because each time the cycle is done one atom of carbon is produced, so six carbon atoms are needed for the production of fructose and other similar plant compounds that are consisted of exactly six carbon atoms.This Process is also called as DARK Cycle Reaction.
Products of the Calvin cycle
The immediate product of the Calvin cycle is glyceraldehyde-3-phosphate (G3P) and water. Two G3P molecules (or one F6P molecule) that have exited the cycle are used to make larger carbohydrates. In simplified versions of the Calvin cycle they may be converted to F6P or F5P after exit, but this conversion is also part of the cycle.
See also
References
- Bassham, J.A. (2003). Mapping the carbon reduction cycle: a personal retrospective. Photosynthesis Research, volume 76, pages 25-52 (see: ).Mario Otmman (1998)
- Diwan, Joyce J. (2005). Photosynthetic Dark Reaction at
The
Calvin cycle (or
Calvin-Benson cycle or carbon fixation) is a series of
biochemistry reactions that takes place in the stroma of chloroplasts in
photosynthesis organisms. It was discovered by
Melvin Calvin and
Andrew Benson at the
University of California, Berkeley with
James Bassham also contributing. It is one of the light-independent reactions or dark reactions.
Steps of the Calvin cycle
- The enzyme RuBisCO catalyses the carboxylation of Ribulose-1,5-bisphosphate, a 5 carbon compound, by carbon dioxide (a total of 6 carbons). Rubisco is a large, slow enzyme averaging 3 substrate per second compared to 1000/s of most other enzyme in the Calvin cycle. Two molecules of glycerate 3-phosphate, a 3-carbon compound, are created. (also: 3-phosphoglycerate, 3-phosphoglyceric acid, 3PGA)
- The enzyme phosphoglycerate kinase catalyses the phosphorylation of 3PGA by ATP (which was produced in the light-dependent stage). 1,3-bisphosphoglycerate (glycerate-1,3-bisphosphate) and Adenosine diphosphate are the products. (However, note that two PGAs are produced for every CO2 that enters the cycle, so this step happens twice.)
- The enzyme G3P dehydrogenase catalyses the redox of 1,3BPGA by NADPH (which was another product of the light-dependent stage). Glyceraldehyde 3-phosphate (also G3P, GP) is produced, and the NADPH itself was oxidised and hence becomes NADP+.
(Simplified versions of the Calvin cycle integrate the remaining steps, except for the last one, into one general step - the regeneration of RuBP - also, one G3P would exit here.)
- Triose phosphate isomerase converts some G3P reversibly into dihydroxyacetone phosphate (DHAP), also a 3-carbon molecule.
- Aldolase and Fructose-1,6-bisphosphatase convert some of these two into fructose-6-phosphate (6C). A phosphate ion is lost into solution.
Up to this point, as per the overall equation given above, 6 carbon dioxide molecules would have been converted, with the use of 6 RuBP, 12 ATP and 12 NADPH, to 12 G3P molecules. One F6P, (= 2 G3P) then exits the cycle, while 10 of these G3P molecules continue, giving a ratio of 1:5 G3P. Obviously, the ratio of carbon dioxide entering the cycle to RuBP already present is also 1:5.
- F6P is then combined with another G3P (total 9C) and then cleaved into xylulose-5-phosphate (X5P) and erythrose-4-phosphate by transketolase.
- E4P and DHAP are converted into sedoheptulose-1,7-bisphosphate (7C) by a transaldolase enzyme.
- S7P is then combined with another G3P (total 10C) and then cleaved into another X5P and ribose-5-phosphate (R5P) again by transketolase.
- Finally, phosphoribulokinase phosphorylates RuP into RuBP, ribulose-1,5-bisphosphate, completing the Calvin cycle. This requires the input of one ATP.
All the G3P produced earlier is converted into RuBP (5C), so 10 G3Ps (30C, 10 phosphates) were needed to produce 6 RuBPs (30C, 6 phosphates). 6 ATPs were also needed in the last step, giving a total of 18 ATPs used up per 6 CO2s. However, four phosphate ions are lost and these also form ATP. The energy in those ATPs is used to drive some of the reactions.
At high temperatures, RuBisCO will react with O2 instead of CO2 in
photorespiration. This turns RuBP into 3PGA and 2-phosphoglycolate, a 2-carbon molecule which can be converted into 3PGA, some of which will exit the Calvin cycle. However, if this continues the RuBP will eventually be depleted, which slows down the cycle if electrons are entering from the light-dependent reaction too quickly.
The cycle has to be repeated for six times, because each time the cycle is done one atom of carbon is produced, so six carbon atoms are needed for the production of
fructose and other similar plant compounds that are consisted of exactly six carbon atoms.This Process is also called as DARK Cycle Reaction.
Products of the Calvin cycle
The immediate product of the Calvin cycle is glyceraldehyde-3-phosphate (G3P) and water. Two G3P molecules (or one F6P molecule) that have exited the cycle are used to make larger carbohydrates. In simplified versions of the Calvin cycle they may be converted to F6P or F5P after exit, but this conversion is also part of the cycle.
See also
References
- Bassham, J.A. (2003). Mapping the carbon reduction cycle: a personal retrospective. Photosynthesis Research, volume 76, pages 25-52 (see: ).Mario Otmman (1998)
- Diwan, Joyce J. (2005). Photosynthetic Dark Reaction at
Calvin cycle - Wikipedia, the free encyclopedia
The Calvin cycle (or Calvin-Benson-Bassham cycle or carbon fixation) is a series of biochemical reactions that takes place in the stroma of chloroplasts in photosynthetic organisms ...
The Calvin Cycle
The Calvin cycle is a metabolic pathway found in the stroma of the chloroplast in which carbon enters in the form of CO 2 and leaves in the form of sugar.
calvin
This animation of the Calvin cycle is designed to show, in 3 stages, the major events in the synthesis of sugar in the stroma of chloroplasts.
Calvin cycle (carbon fixation)
Calvin Cycle (carbon fixation stages) When cursor points to a box further details will be displayed in the status window below. If you click on the box you will change to ...
Calvin Cycle
Step 2: Calvin Cycle. The second stage of photosynthesis, which takes place in the stroma of the chloroplast, can occur without the presence of sunlight.
Calvin cycle 2
Calvin Cycle. When cursor points to a box further details will be displayed in the status window below. If you click on the box you will change to appropriate reaction scheme or ...
The Calvin Cycle
The Calvin Cycle Process. The BIG Picture! Before continuing, be sure to familiarize yourself with the . important players in the Calvin Cycle by going here.
Calvin Cycle
Light reactions: Energy of light is conserved as “high energy” phosphoanhydride bonds of ATP; reducing power of NADPH. Proteins & pigments responsible for the light ...
Definition: calvin cycle from Online Medical Dictionary
The Online Medical Dictionary is a searchable dictionary of definitions from medicine, science and technology.
photosynthesis dark phase
animated outline of photosynthesis light-independent (or “dark”) phase . photosynthesis light phase. INDEX. This animation is the copyrighted property of John Kyrk.
