Calvin Cycle

Calvin Cycle - O2 consumption& CO2 production Ø Some...

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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 Ø Some plants have evolved alternative means to deliver CO2 by forming 4-carbon compounds Ø 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 Ø Stomata open at night, incorporating CO2 into organic acids Ø Organic acids stored in vacuole Ø 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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This note was uploaded on 03/28/2008 for the course BIOL 212 taught by Professor Shen during the Spring '08 term at Iowa State.

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Calvin Cycle - O2 consumption& CO2 production Ø Some...

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