Electron transport chain


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  • Oxidation refers to the loss of electrons to any electron acceptor, not just to oxygen. Uses exergonic flow of electrons through ETC to pump H+ across membrane.
  • Pumping H+ across membrane … what is energy to fuel that? Can’t be ATP! that would cost you what you want to make! Its like cutting off your leg to buy a new pair of shoes. :-( Flow of electrons powers pumping of H + O 2 is 2 oxygen atoms both looking for electrons
  • Electrons move from molecule to molecule until they combine with O & H ions to form H 2 O It’s like pumping water behind a dam -- if released, it can do work
  • Chemiosmosis is the diffusion of ions across a membrane. More specifically, it relates to the generation of ATP by the movement of hydrogen ions across a membrane. Hydrogen ions (protons) will diffuse from an area of high proton concentration to an area of lower proton concentration. Peter Mitchell proposed that an electrochemical concentration gradient of protons across a membrane could be harnessed to make ATP. He likened this process to osmosis, the diffusion of water across a membrane, which is why it is called chemiosmosis.
  • Where did the glucose come from? from food eaten Where did the O 2 come from? breathed in Where did the CO 2 come from? oxidized carbons cleaved off of the sugars (Krebs Cycle) Where did the CO 2 go? exhaled Where did the H 2 O come from? from O 2 after it accepts electrons in ETC Where did the ATP come from? mostly from ETC What else is produced that is not listed in this equation? NAD, FAD, heat!
  • What if you have a chemical that punches holes in the inner mitochondrial membrane?
  • Electron transport chain

    1. 1. Cellular Respiration Stage 4: Electron Transport ChainAP Biology 2006-2007
    2. 2. Cellular respirationAP Biology
    3. 3. What’s the point? The point is to make ATP! ATPAP Biology 2006-2007
    4. 4. 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! There’s got to be a better way! I need a lot more ATP! A working muscle recycles overAP Biology 10 million ATPs per second
    5. 5. There 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 O (aerobic respiration) 2 That sounds more O2AP Biology like it!
    6. 6. Mitochondria  Double membrane  outer membrane  inner membrane  highly folded cristae  enzymes & transport proteins  intermembrane space  fluid-filled space between membranes Oooooh! Form fitsAP Biology function!
    7. 7. Electron Transport Chain Inner mitochondrial Intermembrane space membrane C Q NADH cytochrome cytochrome c dehydrogenase bc complex oxidase complex Mitochondrial matrixAP Biology
    8. 8. Remember the Electron Carriers? glucose Krebs cycleGlycolysis G3P 2 NADH 8 NADH 2 FADH2 Time to break openthe piggybank!AP Biology
    9. 9. Electron Transport ChainNADH → NAD+ + H Building proton gradient! e intermembrane space p H+ H+ H+ inner mitochondrialH → e- + H+ C membrane Q e– e – H e– FADH2 FAD NADH H 2H+ + 1 O2 H2O NAD + 2 NADH cytochrome cytochrome c dehydrogenase bc complex oxidase complex mitochondrial matrixAP Biology What powers the proton (H+) pumps?…
    10. 10. Stripping 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+ H + TA-DA!! H H + + H H + + H H+ + H+ H+ H H+ + Moving electrons do the work! C Q e– e– e – FADH2 FAD ADP 1 NADH 2H+ + O2 H2O + Pi NAD+ 2 NADH cytochrome cytochrome c dehydrogenase bc complex oxidase complex ATPAP Biology H+
    11. 11. But what “pulls” theelectrons down the ETC? H 2O O2 electrons flow downhillAP Biology to O2 oxidative phosphorylation
    12. 12. Electrons flow downhill  Electrons move in steps from carrier to carrier downhill to oxygen  each carrier more electronegative  controlled oxidation  controlled release of energy make ATP instead of fire!AP Biology
    13. 13. “proton-motive” force We did it! H+ H+ H+ H+  Set up a H+ H+ H + H+ H+ gradient  Allow the protons to flow through ATP synthase  Synthesizes ATP ADP + Pi ADP + Pi → ATP Are we ATP there yet? H+AP Biology
    14. 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’s the point!AP Biology
    15. 15. 1961 | 1978 Peter Mitchell  Proposed chemiosmotic hypothesis  revolutionary idea at the time proton motive force 1920-1992AP Biology
    16. 16. Pyruvate from Intermembrane Inner H+ cytoplasm space mitochondrial H + membrane Electron transport C system Q NADH e- 2. Electrons H+ provide energy 1. Electrons are harvested to pump Acetyl-CoA and carried to the e- transport system. protons across the membrane. NADH e- H2O Krebs e 3. Oxygen joins - 1 O FADH2 with protons to cycle 2 +2 O2 form water. 2H+ CO2 H+ ATP H+ ATP ATP 4. Protons diffuse back in down their concentration ATP Mitochondrial gradient, driving the synthase matrix synthesis of ATP.AP Biology
    17. 17. ~4 Cellular respiration 0 AT P 2 ATP + 2 ATP + ~36 ATPAP Biology
    18. 18. Summary of cellular respiration C6H12O6 + 6O2 → 6CO2 + 6H2O + ~40 ATP  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?AP Biology
    19. 19. Taking it beyond… H+ H+ H+  What is the final electron acceptor in Q e– C e– Electron Transport Chain? e – FADH2 FAD 1 NADH 2H+ + O2 H2O NAD+ O2 2 NADH cytochrome cytochrome c dehydrogenase bc complex oxidase complex  So what happens if O2 unavailable?  ETC backs up  nothing to pull electrons down chain  NADH & FADH can’t unload H 2  ATP production ceases  cells run out of energyAP Biology  and you die!
    20. 20. What’s the point? The point is to make ATP! ATPAP Biology 2006-2007