Cellular Respiration Stage 4: Electron Transport Chain

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Cellular Respiration Stage 4: Electron Transport Chain. Cellular respiration. What’s the point?. The point is to make ATP !. ATP. ATP accounting so far…. Glycolysis  2 ATP Kreb’s cycle  2 ATP Life takes a lot of energy to run, need to extract more energy than 4 ATP !.
Cellular RespirationStage 4: Electron Transport ChainCellular respirationWhat’s thepoint?The pointis to makeATP!ATPATP accounting so far…
  • Glycolysis 2ATP
  • Kreb’s cycle 2ATP
  • Life takes a lot of energy to run, need to extract more energy than 4 ATP!
  • There’s got to be a better way!I need a lotmore ATP!A working muscle recycles over 10 million ATPs per secondO2There is a better way!
  • Electron Transport Chain
  • series of proteins built into inner mitochondrial membrane
  • along cristae
  • transport proteins& enzymes
  • transport of electrons down ETC linked to pumping of H+ to create H+ gradient
  • yields ~36 ATP from 1 glucose!
  • only in presence of O2 (aerobic respiration)
  • Thatsounds morelike it!Mitochondria
  • Double membrane
  • outer membrane
  • inner membrane
  • highly folded cristae
  • enzymes & transport proteins
  • intermembrane space
  • fluid-filled space between membranes
  • Oooooh!Form fits function!InnermitochondrialmembraneElectron Transport ChainIntermembrane spaceCQcytochromebc complexcytochrome coxidase complexNADH dehydrogenaseMitochondrial matrixRemember the Electron Carriers? glucoseKrebs cycleGlycolysisG3P8 NADH2 FADH22 NADHTime tobreak openthe piggybank!ep12Electron Transport ChainBuilding proton gradient!NADH  NAD+ + HintermembranespaceH+H+H+innermitochondrialmembraneH  e- + H+Ce–Qe–He–FADH2FADHNADH 2H+ + O2 H2ONAD+cytochromebc complexcytochrome coxidase complexNADH dehydrogenasemitochondrialmatrixWhat powers the proton (H+) pumps?…H+H+H+H+H+H+H+H+H+H+H+H+Ce–Qe–12e–FADH2FADNADH 2H+ + O2 H2ONAD+cytochromebc complexNADH dehydrogenasecytochrome coxidase complexStripping H from Electron Carriers
  • Electron carriers pass electrons & H+ to ETC
  • H cleaved off NADH & FADH2
  • electrons stripped from H atoms  H+ (protons)
  • electrons passed from one electron carrier to next in mitochondrial membrane (ETC)
  • flowing electrons = energy to do work
  • transport proteins in membrane pump H+ (protons) across inner membrane to intermembrane space
  • H+H+H+TA-DA!!Moving electronsdo the work!ADP+ PiATPH2OO2But what “pulls” the electrons down the ETC?oxidative phosphorylationElectrons flow downhill
  • Electrons move in steps from carrier to carrier downhill to oxygen
  • each carrier more electronegative
  • controlled oxidation
  • controlled release of energy
  • H+H+H+H+H+H+H+H+ADP + PiH+“proton-motive” forceWe did it!
  • Set up a H+ gradient
  • Allow the protonsto flow through ATP synthase
  • Synthesizes ATP
  • ADP + PiATPATPChemiosmosis
  • The diffusion of ions across a membrane
  • build up of proton gradient just so H+ could flow through ATP synthase enzyme to build ATP
  • Chemiosmosis links the Electron Transport Chain to ATP synthesis1961 | 1978Peter Mitchell
  • Proposed chemiosmotic hypothesis
  • revolutionary idea at the time
  • proton motive force1920-1992IntermembranespacePyruvate fromcytoplasmInnermitochondrialmembraneH+H+ElectrontransportsystemCQNADHe-H+2. Electrons provide energy to pump protons across the membrane.1. Electrons are harvested and carried to the transport system.e-Acetyl-CoANADHe-H2Oe-Krebscycle3. Oxygen joins with protons to form water.1FADH2O22O2+2H+H+CO2ATPH+ATPATP4. Protons diffuse back indown their concentrationgradient, driving the synthesis of ATP.ATPsynthaseMitochondrial matrix~40 ATPCellular respiration++2 ATP2 ATP~36 ATPC6H12O6+6CO2+6H2O+~40 ATP6O2Summary of cellular respiration
  • Where did the glucose come from?
  • Where did the O2 come from?
  • Where did the CO2 come from?
  • Where did the CO2 go?
  • Where did the H2O come from?
  • Where did the ATP come from?
  • What else is produced that is not listed in this equation?
  • Why do we breathe?
  • H+H+H+Ce–Qe–12e–FADH2FADNADH 2H+ + O2 H2ONAD+cytochromebc complexNADH dehydrogenasecytochrome coxidase complexTaking it beyond…
  • What is the final electron acceptor in Electron Transport Chain?
  • O2
  • So what happens if O2 unavailable?
  • ETC backs up
  • nothing to pull electrons down chain
  • NADH & FADH2 can’t unload H
  • ATP production ceases
  • cells run out of energy
  • and you die!
  • What’s thepoint?The pointis to makeATP!ATP
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