费晓方《细胞生物学》07chapter5ii energy generation in mitochondria and chloroplasts.ppt

Chloroplast and photosynthesis,Comparison of a mitochondrion and a chloroplast.,The chloroplast. This photosynthetic organelle contains three distinct membranes (the outer membrane, the inner membrane, and the thylakoid membrane) that define three separate internal compartments (the intermembrane space, the stroma, and the thylakoid space). The thylakoid membrane contains all of the energy-generating systems of the chloroplast. In electron micrographs this membrane appears to be broken up into separate units that enclose individual flattened vesicles but these are probably joined into a single, highly folded membrane in each chloroplast. As indicated, the individual thylakoids are interconnected, and they tend to stack to form aggregates called grana.,1、Chloroplast membrane,(A) A wheat leaf cell in which a thin rim of cytoplasm containing chloroplasts surrounds a large vacuole. (B) A thin section of a single chloroplast, showing the starch granules and lipid droplets that have accumulated in the stroma as a result of the biosyntheses occurring there. (C) A high-magnification view of a granum, showing its stacked thylakoid membrane. (Courtesy of K. Plaskitt.),2、Stroma,Stroma contains many metabolic enzyme and its own genome and genetic system. Stroma also contains a special set of ribosomes, RNA and DNA. 核酮糖-1，5-二磷酸羧化酶/加氧酶（rebulose-1,5-biphosphate carboxylase/oxygenase, Rubisco),3、Thylakoid,Grana Granum thylakoid Stroma lamella Stroma thylakoid,The thylakoid membrane contain all the light-capturing systems, the electron-transport chain, and ATP synthase.,Five protein complex: PSII PSI Cytochrome b6/f complex CF0-CF1 ATP synthase Chla/b light-harvesting complex,The main function of chloroplast,photosynthesis,Light reaction,Carbon-fixation reaction,Primary reaction,Photosynthetic electron transfer chain,Photophosphorylation,C4,C3,CAM,Pigment,-CHO in chl b,Prophyrin ring,The ratio of chl a and chl b is 3:1 The ratio of chlorophyll and carotenoid is 3:1,Pigment contain chlorophyll, carotenoid and phycobilin. Chlorophyll contain chl a and chl b. Carotenoid is accessory pigment. The main type contain -carotene and lutein.,Primary reaction,约300个叶绿素分子和一些肽链构成。 全部叶绿素b和大部分叶绿素a都是天线色素。,集光复合体,The antenna complex and photochemical reaction center in a photosystem,Pheo in PII,Chla（A0） in PI,Photosynthetic electron transfer chain,photosystem I photosystem II cytochrome b6/f complex,Photosystem II P680,14 chlorophyll molecule,吸收高峰为波长680nm处，又称P680 。至少包括12条多肽链。位于EFs, EFu上，基粒与基质非接触区域的类囊体膜上。包括一个集光复合体（light-hawesting comnplex ，LHC ）、一个反应中心和一个含锰原子的放氧复合体（oxygen evolving complex）。,D1多肽链上的酪氨酸残基,COO-,C,H3N+,H,CH2,OH,M,M3+,M2+,M+,M4+,cytochrome b6/f complex,可能以二聚体形成存在，每个单体含有四个不同的亚基。细胞色素b6（b563）、细胞色素f、铁硫蛋白、以及亚基（被认为是质体醌的结合蛋白）。,（PSI） P700,能被波长700nm的光激发，又称P700 。包含多条肽链，位于基粒与基质接触区和基质类囊体膜中。由集光复合体和作用中心构成。结合100个左右叶绿素分子、除了几个特殊的叶绿素为中心色素外，其它叶绿素都是天线色素。三种电子载体分别为A0（一个chla分子)、A1(为维生素K1)及3个不同的4Fe-4S。,Light-dependent reaction: Electron transport in the thylakoid membrane and noncyclic photophosphorylation:,Noncyclic photophosphorylation,Cyclic photophosphorylation:,Cyclic photophosphorylation,PSI and PSII,Photosynthesis in a chloroplast. Water is oxidized and oxygen is released in the photosynthetic electron-transfer reactions, while carbon dioxide is assimilated (fixed) to produce carbohydrate in the carbon-fixation reactions.,Changes in redox potential during photosynthesis.,光合过程中氧化还原电势的变化,Photosynthesis,? resemblance ? difference,Comparison of a mitochondrion and a chloroplast.,叶绿体功能示意图,叶绿体的ATP合成酶结构示意图,叶绿体类囊体膜中进行光合磷酸化的图解,叶绿体类囊体膜上进行光合磷酸化,（三）暗反应 C3途径(C3 pathway)：亦称卡尔文 (Calvin)循环。CO2受体为RuBP，最初产物为3-磷酸甘油酸(PGA)。 C4途径(C4 pathway) ：亦称哈奇-斯莱克(Hatch-Slack)途径，CO2受体为PEP，最初产物为草酰乙酸(OAA)。 景天科酸代谢途径（Crassulacean acid metabolism pathway，CAM途径）：夜间固定CO2产生有机酸，白天有机酸脱羧释放CO2，进行CO2固定。,碳固定的循环,类囊体膜上光合过程中的电子流动,Carbon dioxide fixation and the synthesis of carbohydrate in C3 plants (Calvin cycle),Figure 14-43 The initial reaction in carbon fixation. This reaction, in which carbon dioxide is converted into organic carbon, is catalyzed in the chloroplast stroma by the abundant enzyme ribulose bisphosphate carboxylase. The product, 3-phosphoglycerate, is also an important intermediate in glycolysis: the two carbon atoms shaded in blue are used to produce phosphoglycolate when the enzyme adds oxygen instead of CO2。,The structure and function in C4 plants,4. Organelle DNA and protein importing,A. Organelle DNA,The size range of organelle DNA is similar to that of viral DNAs. Mit DNA: from 300,000bp (some land plants). DNA of Mit genome (in mammals) 16,500bp(0.001% of nuclear genome) ; Chl genomes are about 10 times larger and contain about 120 genes. Chl DNA: from 70,000to 200,000bp (genome of land plants);,Genes in mtDNA encode rRNAs, tRNAs, and some mitochondrial proteins Human mt DNA: 16,569bp 2 rRNAs, 22 tRNAs, 13 polypeptides: NADH reductase. 7 sub. Cty b-c1 complex. 1 cytb Cyt oxidase. 3 subunits ATP synthase: 2 F0 sub,Products of mt genes are not exported,The organization of the liverwort(地钱) Chl genome,B. Mit and Chl have their own genetic systems,Mit and Chl are organelles semiautocephaly. The synthesis of mt proteins is coordinated,C. The transport protein into Mit. And Chl.,Tree proteins translocators in Mit membranes:,TOM, TIM,and OXA complex are multimeric membrane protein, that catalyze protein transport across Mit membrane, TOM, TIM stand for translocase of the outer and inner Mit membranes respectively. TOM functions across the outer membrane; TIM(TIM23 and TIM22) function across the inner membrane. OXA mediates the insertion of inner membrane proteins that are synthesized within the Mit. OXA also helps TOM and TIM to insert some proteins into the matrix.,Translocation of precursors to the matrix occurs at the sites where the outer and inner membranes are close together;,The protein import by Mit:,N-terminal signal sequence is recognized by receptors of TOM; The protein is translocated across both Mit membranes at or near special contact sites.,Only unfolded proteins can be imported into Mit;,Mit precursor proteins remain unfolded through interactions with hsp70 chaperone proteins in the cytosol after they are synthesized.,ATP hydrolysis and H+ gradient are used to dtive protein import into Mit,Protein transport into the inner Mit membrane and the intermembrane space requires two signal sequences,Two signal sequences are required to direct proteins to the Thylakoid membrane in Chl.,Translocation into thylakoid space or thylakoid M can occur by any one of at least four routes.,5. The proliferation and origin of Mit and Chl.,A. Organelle growth and division determine the number of Mitochondria and Plastids in a cell,Mit fission and fusion (a dividing Mit in a liver cell); Dividing or Budding of Mit. Chloroplasts: dividing and formation of chloroplasts from proplastids begins by the light-induced budding of the inner membrane.,B. Origin: The endosymbiont theory,Compare the ribosomal RNA with the base sequence of various bacterial rRNAs: Purple bactria-Mitochondria Cyanobacteria-Chloroplasts,Suggested evolutionary pathway for the origin of Mit.,NAD （nicotinamide adenine dinucleotide）， NADP,Flavin mononucleotide(FMN)& Flavin adenine dinucleotide,细胞色素：含血红素铁，通过Fe3+/ Fe2+变化传递电子，包括细胞色素a、a3、b、c、c1，其中a、a3含有铜原子。,铁硫蛋白：分子结构中每个铁原子和4个硫原子结合，通过Fe3+/Fe2+互变进行电子传递，有2Fe-2S和4Fe-4S两种类型。,辅酶Q：脂溶性小分子醌类化合物，有3种形式，即：氧化型醌Q，还原型氢醌QH2和自由基半醌QH。,