Glucose metabolism Glycolysis: 2 NADH, 2 ATP (net) Pre-TCA cycle: 2 NADH TCA cycle: 6 NADH, 2 FADH 2, 2 A/GTP Some ATP Big bonus: NADH, FADH 2 → REDUCING

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    04-Jan-2016

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  • Glucose metabolismGlycolysis: 2 NADH, 2 ATP (net)

    Pre-TCA cycle: 2 NADH

    TCA cycle: 6 NADH, 2 FADH2, 2 A/GTP

    Some ATPBig bonus: NADH, FADH2 REDUCING POWER

  • Energy harvest by respirationCarbon-carbon bonds: chemical energy

    NADH, FADH2: energy of oxidation Proton gradient: potential energy

    ATP synthesis: useable chemical energy

  • Reducing power/Energy of oxidationNot very user-friendlyHow to harvest the energy?

    Electron transport chainChange energy of oxidation into potential energy (H+ gradient)Change potential energy into chemical energy(F1Fo ATP synthase)

  • What is energy of oxidation?Reducing potentials:NAD+ + H+ + 2e- NADH E' ~ -0.414Vubiquinone + 2H+ + 2e- ubiquinol E' ~ +0.045

    Electrons (e-) flow spontaneously from NADH to ubiquinoneNADHubiquinone(reduced form)(oxidized form)NADH IS A STRONGER REDUCING AGENT THAN UBIQUINOL

  • Cataloging the red/ox reactionTransfer of e- from NADH to ubiquinoneNADH NAD+ + H+ + 2e-ubiquinone + 2H+ + 2e- ubiquinolNADH + ubiquinone + H+ ubiquinol + NAD+E' (V)+0.414+0.045+0.459*extra energy*not yet useableDE' > 0 ~ DG' < 0

  • Electrons are passed among redox carriersNADHNAD+FMN (FMNH2)Fe-S ClusterUbiquinone (coenzyme Q)Cytochrome CO2H2OREDUCING STRENGTHCouple energetically favorable reactionsto energetically unfavorable reactionsOverall -DG

  • MATRIXGeneration of NADHINTERMEMBRANE SPACERedox energy is transformed into potential energy

  • MATRIXINTERMEMBRANE SPACEHigh pH (lower [H+])Electrically negativeLow pH (higher [H+])Electrically positiveFlow of H+ into the matrixIs energetically favorable 1. Input energy to move H+ out 2. Harvest energy

  • Mitochondria actually look like the cartoonshttp://www.tmd.ac.jp/http://faculty.ircc.edu

  • Redox energy is transformed into potential energyEstablishment of a chemical and electric gradient across the inner membraneF1Fo ATP synthaseTransforms potentialEnergy into useableChemical energy

  • Electron transport between electron carriers occurs in protein complexes within the inner membrane

  • Complex INADH: Ubiquinone oxidoreductase 850kDa, 43 subunitsConverts NADH to NAD+e- transferred through complexFMN, Fe-S clusters4 protons are pumped from the matrix into the intermembrane spaceReduces ubiquinone (Q) to ubiquinol (QH2)

  • Ubiquinol (reduced coenzyme Q)

  • Complex IIICoenzyme Q:cytochrome c oxidoreductase250 kDa11 subunits2 coQ oxidized, one CytC reducede- carriers:Hemes, Fe-S clustersNet 4 H+ pumped to intermembrane space

  • Complex III, cont.

  • Cytochrome CHeme group carries electronsLoosely associated with membraneShuttles e- from complex III to IV

  • Complex IVCytochrome C oxidase160 kDa13 subunitsReduces oxygen O2 + 2H+ + 2e- H2O

  • Complex II (Use of FADH2)Succinate dehydrogenaseMembrane-bound enzyme in the TCA cycle140 kDa4 subunitsFAD, Fe-S clusters carry electronse- transferred ubiquinone(Q)QH2 carries e- to complex 3

  • Electron transport

  • Overall reaction starting with 2 e- from one NADHNADH + H+ + O2 NAD+ + H2ODG' ~ -220 kJ/mol (of NADH)

    -highly favorable-coupled to transport of ~10 H+ against a chemical/electrical gradient

  • Oxidative phosphorylationInvolves reduction of O2 to H2O by NADH and FADH2ATP synthesized through e- transfers

    Inner mitochondrial membraneEmbedded protein complexesSuccinate dehydrogenaseImpermeable to most small molecules (and H+)Creation of electrochemical gradients

  • ATP generation2 NADH, 2 ATP from glycolysis (glucose)1 NADH from pre-TCA (each pyruvate)3 NADH, FADH2 from TCA (each acetyl CoA)2 e- from NADH yields 2.5 ATP*2 e- from FADH2 yields 1.5 ATP

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