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Cellular Respiration Stage 4: Electron Transport Chain

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 !.

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Cellular Respiration Stage 4: Electron Transport Chain

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  1. Cellular RespirationStage 4: Electron Transport Chain

  2. Cellular respiration

  3. What’s thepoint? The pointis to makeATP! ATP

  4. ATP 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! What’s the point? A working muscle recycles over 10 million ATPs per second

  5. O2 There is a better way! • Electron Transport Chain • series of molecules 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 ~34 ATP from 1 glucose! • only in presence of O2 (aerobic respiration) Thatsounds morelike it!

  6. Mitochondria • Double membrane • outer membrane • inner membrane • highly folded cristae • enzymes & transport proteins • intermembrane space • fluid-filled space between membranes Oooooh!Form fits function!

  7. Innermitochondrialmembrane Electron Transport Chain Intermembrane space C Q cytochromebc complex cytochrome coxidase complex NADH dehydrogenase Mitochondrial matrix

  8. Remember the Electron Carriers? glucose Krebs cycle Glycolysis G3P 8 NADH 2 FADH2 4 NADH Time tobreak openthe bank!

  9. e p 1 2 Electron Transport Chain Building proton gradient! NADH  NAD+ + H intermembranespace H+ H+ H+ innermitochondrialmembrane H  e- + H+ C e– Q e– H e– FADH2 FAD H NADH 2H+ + O2 H2O NAD+ cytochromebc complex cytochrome coxidase complex NADH dehydrogenase mitochondrialmatrix What powers the proton (H+) pumps?…

  10. H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ H+ C e– Q e– 1 2 e– FADH2 FAD NADH 2H+ + O2 H2O NAD+ cytochromebc complex NADH dehydrogenase cytochrome coxidase complex Stripping H from Electron Carriers • NADH passes electrons 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) • transport proteins in membrane pump H+ (protons) across inner membrane to intermembrane space TA-DA!! Moving electronsdo the work! ADP+ Pi ATP

  11. O2 But what “pulls” the electrons down the ETC? electronsflow downhill to O2 oxidative phosphorylation

  12. Electrons flow downhill • Electrons move in steps from carrier to carrier downhill to O2 • each carrier more electronegative • controlled oxidation • controlled release of energy make ATPinstead offire!

  13. H+ H+ H+ H+ H+ H+ H+ H+ ADP + Pi H+ “proton-motive” force We did it! • Set up a H+ gradient • Allow the protonsto flow through ATP synthase • Synthesizes ATP ADP + PiATP ATP Are wethere yet?

  14. Chemiosmosis • 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 synthesis So that’sthe point!

  15. 1961 | 1978 Peter Mitchell • Proposed chemiosmotic hypothesis • revolutionary idea at the time proton motive force 1920-1992

  16. Intermembrane space Pyruvate from cytoplasm Inner mitochondrial membrane H+ H+ Electron transport system C Q NADH e- H+ 2. Electrons provide energy to pump protons across the membrane. 1. Electrons are harvested and carried to the transport system. e- Acetyl-CoA NADH e- H2O e- Krebs cycle 3. Oxygen joins with protons to form water. 1 FADH2 O2 2 O2 + 2H+ H+ CO2 H+ 2 ATP ATP 32 4. Protons diffuse back in down their concentration gradient, driving the synthesis of ATP. ATP synthase Mitochondrial matrix

  17. ~40 ATP Cellular respiration + + + 2 ATP ~2 ATP 2 ATP ~34 ATP

  18. C6H12O6 + 6CO2 + 6H2O + ~40 ATP 6O2 Summary 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?

  19. Taking 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!

  20. What’s thepoint? The pointis to makeATP! ATP

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