细胞生物学：07Chapter5II energy generation in mitochondria and chloroplasts

1、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 sp

2、ace, 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

3、, 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 thi

4、n 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 contain

5、s 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

6、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 Photo

7、synthetic 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 accessor

8、y 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 cyt

9、ochrome b6/f complex Photosystem II P680 14 chlorophyll molecule 吸收高峰为波长吸收高峰为波长680nm处，又称处，又称P680 。 至少包括至少包括12条多肽链。位于条多肽链。位于EFs, EFu上，上， 基粒与基质非接触区域的类囊体膜上。包基粒与基质非接触区域的类囊体膜上。包 括括一个集光复合体一个集光复合体（light-hawesting comnplex ，LHC ）、）、一个反应中心一个反应中心 和和一个含锰原子的放氧复合体一个含锰原子的放氧复合体（oxygen evolving complex）。）。 D1多肽链上的酪

10、氨酸残基 COO- CH3N+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。细胞色素不同的亚基。细胞色素b6（b563）、细胞）、细胞 色素色素f、铁硫蛋白、以及亚基、铁硫蛋白、以及亚基（被认为是（被认为是 质体醌的结合蛋白）。质体醌的结合蛋白）。 （PSI） P700 能被波长能被波长700nm的光激发，又称的光激发，又称P700 。包含多条肽链，位于。包含多条肽链，位于 基粒与基质接触区和基质类囊体膜中。由集光复合体基粒与基质接触区和基质类囊体膜中

11、。由集光复合体和作和作 用中心构成。结合用中心构成。结合100个左右叶绿素分子、除了几个特殊的个左右叶绿素分子、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 载体分别为载体分别为A0（一个（一个chla分子分子)、A1(为维生素为维生素K1)及及3个不同个不同 的的4Fe-4S。 Light-dependent reaction: Electron transport in the thylakoid membrane and noncyclic photophosphorylation: Noncyclic phot

12、ophosphorylation 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-fixati

13、on reactions. Changes in redox potential during photosynthesis. 光合过程中氧化还原电势的变化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功能示意图 叶绿体的叶绿体的ATP合成酶结构示意图合成酶结构示意图 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叶绿体类囊体膜上进行光合磷酸化 （三）

14、暗反应（三）暗反应 C3途径途径(C3 pathway)：亦称卡尔文：亦称卡尔文 (Calvin)循环。循环。 CO2受体为受体为RuBP，最初产物为，最初产物为3-磷酸甘油酸磷酸甘油酸(PGA)。 C4途径途径(C4 pathway) ：亦称哈奇：亦称哈奇-斯莱克斯莱克(Hatch- Slack)途径，途径，CO2受体为受体为PEP，最初产物为草酰乙酸，最初产物为草酰乙酸 (OAA)。 景天科酸代谢途径（景天科酸代谢途径（Crassulacean acid metabolism pathway，CAM途径）：夜间固定途径）：夜间固定CO2产生有机酸，白天产生有机酸，白天 有机酸脱羧释放有机酸

15、脱羧释放CO2，进行，进行CO2固定。固定。 碳固定的循环碳固定的循环 类囊体膜上光合过程中的电子流动类囊体膜上光合过程中的电子流动 vCarbon 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

16、 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 funct

17、ion in C4 plants 4. Organelle DNA and protein importing A. Organelle DNA vThe 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 contai

18、n about 120 genes. Chl DNA: from 70,000 to 200,000bp (genome of land plants); vGenes 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

19、 Products of mt genes are not exported The organization of the liverwort(地钱地钱) 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. vTree proteins translocators in

20、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 memb

21、rane. 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. vTranslocation of precursors to the matrix occurs at the sites where the outer and inner membranes are close together; vThe protein imp

22、ort 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. vOnly unfolded proteins can be imported into Mit; Mit precursor proteins remain unfolded through interactions with hsp70 chaperone protein

23、s in the cytosol after they are synthesized. vATP hydrolysis and H+ gradient are used to dtive protein import into Mit vProtein transport into the inner Mit membrane and the intermembrane space requires two signal sequences vTwo 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 d