Lec 11 Photosynthesis (II) 1-6

Lec 11 Photosynthesis (II) 1-6 - Biol 113 AU2011 Lecture 11...

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1 Lecture 11 Photosynthesis (II) D. The Calvin cycle uses ATP and NADPH to convert CO 2 to sugar E. Alternative mechanisms of carbon fixation have evolved in hot, arid climate F. Two mechanisms to minimize cost of photorespiration G. H 2 0 is not the only reducing agent to provide electrons for CO 2 fixation H. Animations to review cellular respiration and photosynthesis Biol 113 AU2011 Light Fd Cytochrome complex ADP + i H + ATP P ATP synthase To Calvin Cycle STROMA (low H + concentration) Thylakoid membrane THYLAKOID SPACE (high H + concentration) STROMA (low H + concentration) Photosystem II Photosystem I 4 H + 4 H + Pq Pc Light NADP + reductase NADP + + H + NADPH +2 H + H 2 O O 2 e e 1 / 2 Energy released by the ‘fall” of free energy of electrons during transport drives the creation of a proton gradient across the thylakoid membrane Diffusion of H + (protons) across the membrane drives ATP synthesis The ATP is used to drive carbon fixation during Calvin cycle Fig. 10.18 D. The Calvin Cycle Uses ATP and NADPH to Convert CO 2 to Sugar The Calvin cycle, like the citric acid cycle, regenerates its starting material after molecules enter and leave the cycle The cycle builds sugar from smaller molecules by using ATP and the reducing power of electrons carried by NADPH Ribulose bisphosphate (RuBP) 3-Phosphoglycerate Short-lived intermediate Phase 1: Carbon fixation (Entering one at a time) Rubisco Input CO 2 P 3 6 3 3 P P P P ATP 6 6 ADP P P 6 1,3-Bisphosphoglycerate 6 P P 6 6 6 NADP + NADPH i Phase 2: Reduction Glyceraldehyde-3-phosphate (G3P) 1 P Output G3P (a sugar) Glucose and other organic compounds Calvin Cycle 3 3 ADP ATP 5 P Phase 3: Regeneration of the CO 2 acceptor (RuBP) G3P Fig. 10.19 Carbon enters the cycle as CO 2 and leaves as a sugar named glyceraldehyde-3- phosphate (G3P) For net synthesis of 1 G3P, the cycle must take place three times, fixing 3
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This note was uploaded on 01/05/2012 for the course BIO 113 taught by Professor Swenson during the Fall '08 term at Ohio State.

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Lec 11 Photosynthesis (II) 1-6 - Biol 113 AU2011 Lecture 11...

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