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Unformatted text preview: 1 Biol 113 AU2010 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 I. Answering questions about all lectures so far which have been centered on the fundamental concepts and processes of energy transfer/transformation 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. 10.17 Chloroplasts: Capture of Light Energy The chloroplast is a member of a family of organelles called plastids Chloroplasts contain the green pigment chlorophyll, as well as enzymes and other molecules that function in photosynthesis Chloroplasts are found in leaves and other green organs of plants and in algae Chloroplast structure includes: Thylakoids , membranous sacs, stacked to form a granum Stroma , the internal fluid Ribosomes Thylakoid Stroma Granum Inner and outer membranes 1 m Fig. 6.18 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...
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