第七章、在线粒体和叶绿体中的能量产生

1、Energy Generation in Mitochondria and ChloroplastsChapter 7(1) Mitochondria: in all eukaryotic cells The relationship between the structure and function of mit.(2) Chloroplasts: in plant cells The relationship between the structure and function of chl.Mit: Oxidative phosphorylation ATPChl: Photosynt

2、hesis ATP + NADPH SugarA. Mitochondrial structure and functionvThe size and number of mitochondria reflect the energy requirements of the cell.1. Mitochondria and oxidative phosphorylationFigure7-4Relationship between mitochondria and microtubules.Figure7-3Mitochondrial plasticity.Rapidchangesofshap

3、eareobservedwhenamitochondrionisvisualizedinalivingcell.Figure7-5Localization of mitochondria near sites of high ATP utilization in cardiac muscle and a sperm tail.vInner and outer mitochondrial membranes enclose two spaces: the matrix and intermembrane space.Outer membrane: Contains channel-forming

4、 protein, called Porin. Permeable to all molecules of 5000 daltons or less.Inner membrane (Impermeability): Contains proteins with three types of functions:(1) Electron-transport chain: Carry out oxidation reactions; (2) ATP synthase: Makes ATP in the matrix; (3) Transport proteins: Allow the passag

5、e of metabolites Intermembrane space: Contains several enzymes use ATP to phosphorylate other nucleotides.Matrix: Enzymes; Mit DNA, Ribosomes, etc.Figure14-6Fractionation of purified mitochondria into separate components.Thesetechniqueshavemadeitpossibletostudythedifferentproteinsineachmitochondrial

6、compartment.Themethodshown,whichallowstheprocessingoflargenumbersofmitochondriaatthesametime,takesadvantageofthefactthatinmediaoflowosmoticstrengthwaterflowsintomitochondriaandgreatlyexpandsthematrixspace(yellow).Whilethecristaeoftheinnermembraneallowittounfoldtoaccommodatetheexpansion,theoutermembr

7、anewhichhasnofoldstobeginwithbreaks,releasingastructurecomposedofonlytheinnermembraneandthematrix.B. Specific functions localized within the Mit by disruption of the organelle and fractionationLocalization of metabolic functions within the mitochondrionOuter membrane:Phospholipid synthesisfatty acid

8、 desaturationFatty acid elongationInner membrane:Electron transportOxidative phosphorylationMetabolite transportIntermembrane spaceNucleotide phosphorylationMatrixPyruvate oxidationTCA cycle oxidation of fatsDNA replication, RNA transcription, Protein translation2. Molecular basis of oxidative phosp

9、horylationA. Molecular basis of oxidation: Electron- transport chainB. Molecular basis of phosphorylation: ATP synthasev The structure of the ATP synthaseF1 particle is the catalytic subunit;The F0 particle attaches to F1 and is embedded in the inner membrane.F1: 5 subunits in the ratio 3 :3 :1 :1 :

10、1 F F0: 0: 1a1a：2b2b：12c12c vF1 particles have ATP synthase activityv Proton translocation through F0 drives ATP synthesis by F1: Binding Change Model and rotational catalysisBoyer proposed in 1979, and was greatly stimulated by the publication in 1994 of the structure for F1 complex (X-ray) from bo

11、vine heart mitochondriavDirect experimental evidence supporting the rotational catalysis.Japan researcher, Nature 386: 300, 1997.v The ATP synthase is a reversible coupling device v Other roles for the proton-motive force in addition to ATP synthaseC. Mithchells Chemiosmotic theory (1961)vThe pH and

12、 electrical gradient resulting from transport of protons links oxidation to phosphorylation.vWhen electrons are passed to carriers only able to accept electrons, the H+ is translocated across the inner membrane.More than 21026 molecules (160kg) of ATP per day in our bodies.Electrons pass from NADH o

13、r FADH2 to O2, the terminal electron acceptor, through a chain of carriers in the inner membrane (FMN, Fe-S center, Heme group Fe, CoQ);As electrons move through the electron-transport chain, H+ are pumped out across the inner membrane, and form Proton motive force;Electrons move through the inner m

14、embrane via a series of carriers of decreasing redox potentialIf not all the detergent is removed, what will happen?Figure7-26An experiment demonstrating that the ATP synthase is driven by proton flow.Bycombiningalight-drivenbacterialprotonpump(bacteriorhodopsin),anATPsynthasepurifiedfromoxheartmito

15、chondria,andphospholipids,vesicleswereproducedthatsynthesizedATPinresponsetolight.vSummary of the major activities during aerobic respiration in a mitochondrionNADHO2: 3ATP/2e;FADH2 O2 : 2ATP/2e生物氧化产生ATP的统计 一个葡萄糖分子经过细胞呼吸全过程产生多少ATP？ 糖酵解：底物水平磷酸化产生 4 ATP（细胞质） 己糖分子活化消耗 2 ATP（细胞质） 产生 2NADH，经电子传递产生 4或 6 A

16、TP （线粒体）净积累 6 6或或8 8 ATPATP 丙酮酸氧化脱羧：产生 2NADH（线粒体），生成 6 6ATPATP 三羧酸循环：底物水平的磷酸化产生（线粒体）2 2ATPATP； 产生 6NADH（线粒体），生成 1818ATPATP； 产生 2FADH2（线粒体），生成 4 4 ATPATP 总计生成 3636或或38 38 ATPATP 3. Chloroplast and photosynthesisA. Comparison of a mitochondrion and a chloroplast. Figure14-39The chloroplast.Thisphotosy

17、ntheticorganellecontainsthreedistinctmembranes(theoutermembrane,theinnermembrane,andthethylakoidmembrane)thatdefinethreeseparateinternalcompartments(theintermembranespace,thestroma,andthethylakoidspace).Thethylakoidmembranecontainsalloftheenergy-generatingsystemsofthechloroplast.Inelectronmicrograph

18、sthismembraneappearstobebrokenupintoseparateunitsthatencloseindividualflattenedvesicles(seeFigure14-40),buttheseareprobablyjoinedintoasingle,highlyfoldedmembraneineachchloroplast.Asindicated,theindividualthylakoidsareinterconnected,andtheytendtostacktoformaggregatescalledgrana.(A)Awheatleafcellinwhi

19、chathinrimofcytoplasmcontainingchloroplastssurroundsalargevacuole.(B)Athinsectionofasinglechloroplast,showingthestarchgranulesandlipiddropletsthathaveaccumulatedinthestromaasaresultofthebiosynthesesoccurringthere.(C)Ahigh-magnificationviewofagranum,showingitsstackedthylakoidmembrane.(CourtesyofK.Pla

20、skitt.)Figure7-42Photosynthesis in a chloroplast.Waterisoxidizedandoxygenisreleasedinthephotosyntheticelectron-transferreactions,whilecarbondioxideisassimilated(fixed)toproducecarbohydrateinthecarbon-fixationreactions.B. PhotosynthesisC. The antenna complex and photochemical reaction center in a pho

21、tosystemLight-dependent reaction: Electron transport in the thylakoid membrane and noncyclic photophosphorylation: Cyclic photophosphorylation: Changes in redox potential during photosynthesis.vCarbon dioxide fixation and the synthesis of carbohydrate in C3 plants (Calvin cycle)Figure14-43The initia

22、l reaction in carbon fixation.Thisreaction,inwhichcarbondioxideisconvertedintoorganiccarbon,iscatalyzedinthechloroplaststromabytheabundantenzymeribulose bisphosphate carboxylase.Theproduct,3-phosphoglycerate,isalsoanimportantintermediateinglycolysis:thetwocarbonatomsshadedinblueareusedtoproducephosp

23、hoglycolatewhentheenzymeaddsoxygeninsteadofCO2。The structure and function in C4 plants4. Organelle DNA and protein importingA. Organelle DNAvThe 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

24、nuclear genome) ; Chl genomes are about 10 times larger and contain about 120 genes.Chl DNA: from 70,000 to 200,000bp (genome of land plants);vGenes in mtDNA encode rRNAs, tRNAs, and some mitochondrial proteinsHuman mt DNA: 16,569bp 2 rRNAs, 22 tRNAs, 13 polypeptides: NADH reductase. 7 sub. Cty b-c1

25、 complex. 1 cytb Cyt oxidase. 3 subunits ATP synthase: 2 F0 sub Products of mt genes are not exported The organization of the liverwort(地钱地钱) Chl genomeB. Mit and Chl have their own genetic systemsMit and Chl are organelles semiautocephaly. The synthesis of mt proteins is coordinatedC. The transport

26、 protein into Mit. And Chl. vTree 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 mem

27、brane; 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.vTranslocation of precursors to the matrix occurs at the sites where the outer

28、and inner membranes are close together;vThe 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.vOnly unfolded proteins can be imported into Mit;Mit precursor proteins remain unfolded through interactions with hsp70 chaperone proteins in the cytosol after they are syn