Ch20.2 - C a lv in c y c le a c c o u n tin g 3Cs enter as CO2 3 x 5 = 15Cs F ig u r e 2 0 1 4 3 x 6 = 18Cs 3Cs exit as a triose phosphate(net

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Figure 20-14 6 NADPH and 9 ATP required for net synthesis of 1 molecule glyceraldehyde 3-phosphate Calvin cycle “accounting”: 3 x 5 = 15C’s 3 x 6 = 18C’s + 3C’s enter as CO 2 - 3C’s exit as a triose phosphate (net product)
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Overall carbon assimilation “reaction”: 3CO 2 + 9ATP + 6 NADPH + 6H + glyceraldehyde-3-phosphate + 9ADP + 8P i + 6 NADP + The ninth phosphate is incorporated into the triose phosphate itself. So, where does 9th P i come from to regenerate 9 ATP from 9 ADP in the stroma? The P i -triose phosphate antiport system: 20-15 What would happen if this process is blocked?
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Stage 2 of carbon assimilation Glycolytic enzymes 20-16 The P i -triose phosphate antiporter:
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Regulation of carbon assimilation in plants: Figure 20-17/18 What is being shown in the graph below?
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Regulation of carbon assimilation in plants: When photosynthetic reactions are active: stromal pH -- stromal [Mg 2+ ] -- Both conditions promote fructose 1,6-bisphosphatase and Rubisco activity. Figure 20-17/18 (regulation by light)
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Regulation of Calvin Cycle enzymes by formation/reduction of disulfide bonds: What amino acid residues of these enzymes are available for disulfide bond formation? Fig 20-19
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NADP+ is the typical electron acceptor from ferredoxin. But some electrons can be transferred to thioredoxin . Figure 19-56 Regulation of Calvin Cycle enzymes by disulfide bond formation:
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Regulation of Calvin Cycle enzymes by reduction of disulfide bonds: Light-driven redox chain activates: •ribulose 5-phosphate kinase •fructose 1,6-bisphosphatase •sedoheptulose 1,7-bisphosphatase •glyceraldehyde 3-phosphate dehydrogenase Figure 20-19
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Oxidative pentose phosphate pathway (regulation of 1st step): Figure 14-20 G6PDH is inactivated during day (by reducing disulfides) but activated at night (via oxidation); why is the regulation opposite for this enzyme? Glucose 6-phosphate dehydrogenase
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Regulation of carbon dioxide assimilation (summary ): Starch and sucrose synthesized in daylight is used for fuel (via glycolysis) at night. In the dark, carbohydrate metabolism (energy metabolism) in plants resembles that of animals. Rubisco and fructose 1,6-bisphophatase:
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This note was uploaded on 09/21/2010 for the course CH 53380 taught by Professor Raymond during the Spring '10 term at University of Texas at Austin.

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Ch20.2 - C a lv in c y c le a c c o u n tin g 3Cs enter as CO2 3 x 5 = 15Cs F ig u r e 2 0 1 4 3 x 6 = 18Cs 3Cs exit as a triose phosphate(net

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