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Steps of the Calvin Cycle:
(1) The enzyme RuBisCO catalyses the carboxylation of Ribulose-1,5-bisphosphate, a 5 carbon compound, by carbon dioxide (a total of 6 carbons) in a two-step reaction. The initial product of the reaction is a six-carbon intermediate so unstable that it immediately splits in half, forming two molecules of glycerate 3-phosphate, a 3-carbon compound. (also: 3-phosphoglycerate, 3-phosphoglyceric acid, 3PGA)
(2) 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 ADP are the products. (However, note that two PGAs are produced for every CO2 that enters the cycle, so this step utilizes 2ATP per CO2 fixed.
(3) The enzyme G3P dehydrogenase catalyses the reduction of 1,3BPGA by NADPH (which is another product of the light-dependent stage). Glyceraldehyde 3-phosphate (also G3P, GP, TP, PGAL) is produced, and the NADPH itself was oxidized and becomes NADP+. Again, two NADPH are utilized per CO2 fixed.
(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.)
(4) Triose phosphate isomerase converts some G3P reversibly into dihydroxyacetone phosphate (DHAP), also a 3-carbon molecule.
(5) Aldolase and fructose-1,6-bisphosphatase convert a G3P and a DHAP into fructose-6-phosphate (6C). A phosphate ion is lost into solution.
(6) Then fixation of another CO2 generates two more G3P.
(7) F6P has two carbons removed by transketolase, giving erythrose-4-phosphate. The two carbons on transketolase are added to a G3P, giving the ketose xylulose-5-phosphate (Xu5P).
(8) E4P and a DHAP (formed from one of the G3P from the second CO2 fixation) are converted into sedoheptulose-1,7-bisphosphate (7C) by aldolase enzyme.
(9) Sedoheptulose-1,7-bisphosphatase (one of only three enzymes of the Calvin cycle which are unique to plants) cleaves sedoheptulose-1,7-bisphosphate into sedoheptulose-7-phosphate, releasing an inorganic phosphate ion into solution.
(10) Fixation of a third CO2 generates two more G3P. The ketose S7P has two carbons removed by transketolase, giving ribose-5-phosphate (R5P), and the two carbons remaining on transketolase are transferred to one of the G3P, giving another Xu5P. This leaves one G3P as the product of fixation of 3 CO2, with generation of three pentoses which can be converted to Ru5P.
(11) R5P is converted into ribulose-5-phosphate (Ru5P, RuP) by phosphopentose isomerase. Xu5P is converted into RuP by phosphopentose epimerase.
(12) Finally, phosphoribulokinase (another plant unique enzyme of the pathway) phosphorylates RuP into RuBP, ribulose-1,5-bisphosphate, completing the Calvin cycle. This requires the input of one ATP.
SHORTER ANSWER : The Calvin cycle uses ATP and NADPH from the light-depenedent reactions to produce high-energy sugars.
Wiki User
∙ 13y ago
Wiki User
∙ 12y agoSteps of the Calvin Cycle: (1) The enzyme RuBisCO catalyses the carboxylation of Ribulose-1,5-bisphosphate, a 5 carbon compound, by carbon dioxide (a total of 6 carbons) in a two-step reaction. The initial product of the reaction is a six-carbon intermediate so unstable that it immediately splits in half, forming two molecules of glycerate 3-phosphate, a 3-carbon compound. (also: 3-phosphoglycerate, 3-phosphoglyceric acid, 3PGA) (2) 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 ADP are the products. (However, note that two PGAs are produced for every CO2 that enters the cycle, so this step utilizes 2ATP per CO2 fixed. (3) The enzyme G3P dehydrogenase catalyses the reduction of 1,3BPGA by NADPH (which is another product of the light-dependent stage). Glyceraldehyde 3-phosphate (also G3P, GP, TP, PGAL) is produced, and the NADPH itself was oxidized and becomes NADP+. Again, two NADPH are utilized per CO2 fixed. (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.) (4) Triose phosphate isomerase converts some G3P reversibly into dihydroxyacetone phosphate (DHAP), also a 3-carbon molecule. (5) Aldolase and fructose-1,6-bisphosphatase convert a G3P and a DHAP into fructose-6-phosphate (6C). A phosphate ion is lost into solution. (6) Then fixation of another CO2 generates two more G3P. (7) F6P has two carbons removed by transketolase, giving erythrose-4-phosphate. The two carbons on transketolase are added to a G3P, giving the ketose xylulose-5-phosphate (Xu5P). (8) E4P and a DHAP (formed from one of the G3P from the second CO2 fixation) are converted into sedoheptulose-1,7-bisphosphate (7C) by aldolase enzyme. (9) Sedoheptulose-1,7-bisphosphatase (one of only three enzymes of the Calvin cycle which are unique to plants) cleaves sedoheptulose-1,7-bisphosphate into sedoheptulose-7-phosphate, releasing an inorganic phosphate ion into solution. (10) Fixation of a third CO2 generates two more G3P. The ketose S7P has two carbons removed by transketolase, giving ribose-5-phosphate (R5P), and the two carbons remaining on transketolase are transferred to one of the G3P, giving another Xu5P. This leaves one G3P as the product of fixation of 3 CO2, with generation of three pentoses which can be converted to Ru5P. (11) R5P is converted into ribulose-5-phosphate (Ru5P, RuP) by phosphopentose isomerase. Xu5P is converted into RuP by phosphopentose epimerase. (12) Finally, phosphoribulokinase (another plant unique enzyme of the pathway) phosphorylates RuP into RuBP, ribulose-1,5-bisphosphate, completing the Calvin cycle. This requires the input of one ATP.
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What products of the light reactions are used up in the Calvin cycle?
NADPH and ATP
What is the Calvin cycle?
The Calvin cycle is the dark reaction in plants, that results in formation of the glucose molecule. The Calvin Cycle synthesizes G3P Basically, Photosynthesis is divided up into the Light reactions and the Calvin Cycle. The "photo" part is the light reaction part, and the "synthesis" is the Calvin Cycle. The Calvin Cycle's whole existence is to produce sugar. It does this with incorporating CO2 to eventually produce G3P, a sugar that can go on to make glucose etc... The Calvin cycle is powered by NADPH and ATP, which come from the light reactions. Of course this is a simplified version, as there are a number of intermediate molecules, but the idea is the same.For more info I would recommend reading Campbell and Reece (6th ed, 2005)
What events occur during the Calvin cycle?
The Calvin Cycle has 3 series of reactions. They are Carbon Dioxide fixation, Carbon dioxide reduction, and regeneration of the first substrate RuBP ( ribulose 1,5 bisphosphate). It also produces ATP. Glucose is its outcome which is G3P (glyceraldehyde-3-phosphate).
What is cyclic about the reactions that make up the Krebs cycle?
The first reactant and last product are the same.
What is function and structure of stroma?
The stroma of a plant is the region outside of the thylakoid space. This serves two functions in the both the light-dependent and light-independent (Calvin cycle) reactions. In the light-dependent reactions, the H+ ions that build up within the thylakoid begin to form a concentration gradient between the thylakoid and the stroma. As a result, the H+ ions need to diffuse into the stroma. In order to do this, the ions must travel through an enzyme known as ATP synthase. Once it does, the movement of H+ ions through ATP synthase into the stroma provides energy for ADP to become ATP. The ATP formed is an energy source to power the Calvin cycle. Now, the light-independent (Calvin cycle) reactions occur in the stroma.
What products of the light reactions are used up in the Calvin cycle?
NADPH and ATP
Photosynthesis and cellular respiration make up this cycle?
Calvin cycle
What is the Calvin cycle?
The Calvin cycle is the dark reaction in plants, that results in formation of the glucose molecule. The Calvin Cycle synthesizes G3P Basically, Photosynthesis is divided up into the Light reactions and the Calvin Cycle. The "photo" part is the light reaction part, and the "synthesis" is the Calvin Cycle. The Calvin Cycle's whole existence is to produce sugar. It does this with incorporating CO2 to eventually produce G3P, a sugar that can go on to make glucose etc... The Calvin cycle is powered by NADPH and ATP, which come from the light reactions. Of course this is a simplified version, as there are a number of intermediate molecules, but the idea is the same.For more info I would recommend reading Campbell and Reece (6th ed, 2005)
How can photosynthesis be increased by increasing the temperature?
Temperature affects living things mainly by affecting the rate of chemical reactions. These are catalysed by enzymes, which are speeded up by increasing the temperature. The Calvin cycle is a series of chemical reactions, so increasing the temperature increases the rate of reactions in the Calvin cycle and so increases the rate of photosynthesis.
What events occur during the Calvin cycle?
The Calvin Cycle has 3 series of reactions. They are Carbon Dioxide fixation, Carbon dioxide reduction, and regeneration of the first substrate RuBP ( ribulose 1,5 bisphosphate). It also produces ATP. Glucose is its outcome which is G3P (glyceraldehyde-3-phosphate).
What is the cycle about the reactions that make up the Krebs cycle?
The first reactant and last product are the same.
What is cycle about the reactions that make up the Krebs cycle?
The first reactant and last product are the same.
Why is the Calvin cycle sometimes called the dark reactions?
Photosynthesis, mainly the dark reactions which are responsible for the direct production of the product, is a reaction pathway that builds up a complex molecule from smaller molecules, so it is an anabolic pathway. When catabolic means breaking down {repeat: what does a cat do to your furniture} then anabolic means building up.
How many pgal molecules can there be during the Calvin cycle?
There can be up to 12 PGAL molecules during the Calvin cycle
What is cyclic about the reactions that make up the Krebs cycle?
The first reactant and last product are the same.
What two products of the light reactions are used up in the Calvin cycle?
NADPH and ATP
What is function and structure of stroma?
The stroma of a plant is the region outside of the thylakoid space. This serves two functions in the both the light-dependent and light-independent (Calvin cycle) reactions. In the light-dependent reactions, the H+ ions that build up within the thylakoid begin to form a concentration gradient between the thylakoid and the stroma. As a result, the H+ ions need to diffuse into the stroma. In order to do this, the ions must travel through an enzyme known as ATP synthase. Once it does, the movement of H+ ions through ATP synthase into the stroma provides energy for ADP to become ATP. The ATP formed is an energy source to power the Calvin cycle. Now, the light-independent (Calvin cycle) reactions occur in the stroma.
