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國立台灣大學生物資源暨農業學院 植物光生態生理學 (Plant Photo-ecophysiology) 第7章 ATP的合成 楊棋明 博士 中央研究院植物研究所暨生物多樣性研究中心 Email: [email protected] Tel: 02-27821258#612, 613 1 Four stages of photosynthesis in higher plants Stage 1: absorption of light Thylakoid membrane light Chl 2H2O Chl* light O2+4H++4e- Stage 2: electron transport and generation of a proton-motive force (pmf)/pH gradient 2H2O+2NADP+ 2H++2NADPH+O2 Stage 3: synthesis of ATP ADP3-+Pi2- Stroma light ATP4- Stage 4: carbon fixation 6CO2+18ATP4-+12NADPH+12H2O C6H2O+18ADP3-+18Pi2-+12NADP++6H+ 2 Chemical structure of ATP, ADP and AMP and their energy ATP+H2O ADP+H2O AMP+H2O ADP+Pi+ 7.3kcal/mol AMP+Pi+7.3kcal/mol Adenosine+Pi+3.4kcal/mol Adenine 7.3kcal/mol 3.4kcal/mol Ribose 7.3kcal/mol ATP ADP AMP Adenosine 3 ATP synthesis in chloroplast (1): the chemiosmotic hypothesis Pete Mitchell (UK) in 1961 proposed a chemiosmotic hypothesis to account for ATP formation accompanying electron transport in mitochondria and chloroplasts. Pete Mitchell was awarded the Nobel Prize in 1978. Paul Boyer (USA) and John Walker (UK), elucidating the ATPase structure and function, were awarded the Nobel Prize in 1997. The Chemiosmotic Hypothesis: Intact membranes are almost impermeable to the passive flow of protons. The electron donors and acceptors of electron and proton are arranged vectorially in the membrane. During photosynthetic electron transport, protons are translocated from the external medium (stroma) into the osmotic space of the intra-thylakoid membrane. 4 ATP synthesis in chloroplast (2): the chemiosmotic hypothesis 5 ATP synthesis in chloroplast (3): ATPase or ATP synthase/ coupling factors/ CF0CF1 complex Paul Boyer (USA) and John Walker (UK), elucidating the ATPase structure and function, were awarded the Nobel Prize in 1997. 6 Inside-out and outside-in of mitochondrial and chloroplast 7 Construction of artificial ATP synthesis system lumen 8 ATP synthesis (4): bacteria, mitochondria, chloroplast 9 Comparison of chemiosmosis in mitochondria and chloroplasts 10 Subunits and their structures of ATPase complex in eukaryotes ★ (α3β3γδε) C, chloroplast N, nucleus 11 ATPase in the bacteria, mitochondria, chloroplast 12 Rotational model for ATP synthesis ★ ★ ★ ★ ★ ★ 13 Experimental evidence for rotation of ATPase ATPase is a rotatory motor. 14 Mitochondrial ATPase 15 Structure and location of ATPase on the thylakoid membrane 16 Have you a nice day 17