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19 Cards in this Set
- Front
- Back
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Calvin Cycle
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Co2 enters, sugar leaves, ATP is spent and NADPH is consumed
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glyceraldehyde 3 phosphate
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three carbon sugar produced by 3 turns of calvin which fix three molecules of Co2.
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Phase 1 of Calvin Cycle
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Carbon fixation- each co2 is attached to a 5 carbon sugar (RuBP). makes a 6 carbon intermediate that splits to from 2 molecules of 3 phosphoglycerate
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rubisco
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RuBP carboxylase, enzyme that catalyzes first step by adding Co2 to RuBP. most abundant protein on earth.
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Phase 2 of Calvin Cycle
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Reduction- each molecules of 3 phosphoglycerate receives another phosphate from ATP making 1,3-biphosphoglycerate. A pair of electrons from NADPH reduces this to G3P(the sugar made in glycolysis when glucose is split)
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3 molecules of CO2
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6 molecules G3P. 1 molecule is used by a plant cell, but the other 5 must be recycled to regenerate 3 more molecules of RuBP.
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Phase 3 of Calvin Cycle
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Regeneration of Co2 Acceptor (RuBP). Carbon skeletons of G3P are rearranged into 3 RuBP, using three more molecules ATP. From here, the cycle continues.
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one G3P molecule
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calvin cycle consumes 9 ATP and 6 NADPH.
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C3 Plants
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plants whose first step is catalyzed by rubisco and produce 3 phosphoglycerate.
(rice, wheat, soybeans) |
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photorespiration
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consumes oxygen, releases CO2, generates no ATP, decreases photosynthetic output. occurs on hot dry days when stomata close and the o2 concentration in the leaf exceeds that of Co2. wastes CO2.
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C4 Plants
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prefaces the calvin cycle with reaction that incorporate co2 into 4 carbon compounds, the end product of which supplies Co2 for the calvin cycle.
(corn). leaves have bundle sheath cells and mesophyll cells. Co2 is first incorporated into organic intermediates before calvin. |
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bundle-sheath cells
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tightly packed sheaths around the veins of the leaf.
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mesophyll cells
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between the bundle sheath and the leaf surface- more loosely arranged.
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PEP carboxylase
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adds Co2 to phosphophoenolpyruvate (PEP) making 4 carbon oxaloacetate. has a higher affinity for CO2 than does rubisco and thus can fix Co2 when stomata are partially closed.
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crassulacean acid metabolism (CAM)
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co2 entering open stomata during the night is converted into organic acids which release co2 for the calvin cycle during the day when stomata are closed.
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CAM Plants
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mesophyll cells store organic acids in their vacuoles until morning. Co2 is first incorporated into organic intermediates before calvin.
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where are they now: sugar
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supplies entire plant with chemical energy and carbon skeletons to synthesize all the major organic molecules of cells.
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where are they now: organic material
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50% consumed by respiration. stock pile extras by making starch and stores other throughout plant.
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cellulose
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makes up cell walls, most abundant organic material on earth
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