Calvin Cycle

Calvin Cycle - O2 consumption & CO2 production...

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CALVIN CYCLE or CARBON FIXATION v Calvin cycle uses ATP and NADPH to convert CO2 to sugar v Occurs in the stroma
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Three Phases Ø Calvin cycle has three phases Carbon fixation Reduction (2ATP + 2NADPH) Regeneration of the CO2 acceptor (ATP) Ø or each glucose molecule produced requires 18 ATP + 12 NADPH or nearly 80% energy conservation
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(2) 3-PGA ALL carbons are from CO2 phosphorylation reduction G3P: fructose-1,6 bisphosphate hydrolytic product of glycolysis reversal of steps 7 ± 6 of glycolysis Very complex multiple pathways for regeneration (cytoplasm)
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Vein Leaf cross section Mesophyll CO2 O 2 Stomata Hot, dry days, plants close their stomata Conserving water but limiting access to CO2 Causing oxygen to build up
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Photorespiratio n Ø Enzyme Rubisco requires CO2 > 50 ppm Ø Rubisco will "fix" O2 to RuBP , which reduces photosynthetic rate and produces CO2 Ø Photorespiration:
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Unformatted text preview: O2 consumption & CO2 production Some plants have evolved alternative means to deliver CO2 by forming 4-carbon compounds These plants are called C4 plants C4 Plants CO2 is first incorporated into a four carbon acid The acid is then transported into bundle sheath cells for Calvin cycle supplies CO2 directly to Rubisco pyruvate is regenerated back to phosphoenolpyruvate (PEP) by ATP hydrolysis Sp atia l sep ara tion CAM Plants Temporal separation of CO2 fixation and Calvin cycle Stomata open at night, incorporating CO2 into organic acids Organic acids stored in vacuole Stomata close during day, CO2 released from organic acids for Calvin cycle when ample ATP and NADPH from light reactions Stomata closed down: restricted gas diffusion Stomata open only at night (no light for photosynthesis) Photosynthesis Overview...
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Calvin Cycle - O2 consumption & CO2 production...

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