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Cellular Respiration Stage 4: Electron Transport Chain By Kim Foglia, Division Ave. H.S., Levittown, N.Y. Modified by K. Crawford AP/IB Biology 2008-2009 Cellular respiration By Kim Foglia, Divison Ave. H.S., Levittown, N.Y. Modified by K. Crawford AP/IB Biology What’s the point? The point is to make ATP! ATP By Kim Foglia, Division Ave. H.S., Levittown, N.Y. Modified by K. Crawford AP/IB Biology 2008-2009 ATP accounting so far… Glycolysis 2 ATP Krebs cycle 2 ATP Life takes a lot of energy to run, need to extract more energy than 4 ATP! By Kim Foglia, Divison Ave. H.S., Levittown, N.Y. Modified by K. Crawford AP/IB Biology A working muscle recycles over 10 million ATPs per second II. Electron Transport Chain Series of molecules built into inner mitochondrial membrane Along cristae Consists of 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) By Kim Foglia, Divison Ave. H.S., Levittown, N.Y. Modified by K. Crawford AP/IB Biology O2 Electron Transport Chain Inner mitochondrial membrane Intermembrane space C Q NADH dehydrogenase cytochrome bc complex Mitochondrial matrix By Kim Foglia, Divison Ave. H.S., Levittown, N.Y. Modified by K. Crawford AP/IB Biology cytochrome c oxidase complex Remember the Electron Carriers? Glycolysis glucose G3P 4 NADH Time to break open the bank! By Kim Foglia, Divison Ave. H.S., Levittown, N.Y. Modified by K. Crawford AP/IB Biology Oxidation of pyruvate + Citric acid cycle 8 NADH 2 FADH2 Electron Transport Chain Builds a proton gradient! NADH NAD+ + H e p intermembrane space H+ H+ H e- + H+ H+ C e– Q e– NADH H FADH2 NAD+ NADH dehydrogenase inner mitochondrial membrane e– H FAD 2H+ + cytochrome bc complex 1 2 O2 H2O cytochrome c oxidase complex mitochondrial matrix By Kim Foglia, Divison Ave. H.S., Levittown, N.Y. What powers the proton (H+) pumps?… Modified by K. Crawford AP/IB Biology III. 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 H H H H intermembrane space H H H H H + + + + + + H+ + + + H+ C e– NADH Q e– FADH2 FAD NAD+ By Kim Foglia, Divison Ave. H.S., Levittown, NADH N.Y. Modified by K. Crawford AP/IB Biology dehydrogenase e– 2H+ cytochrome bc complex + 1 2 O2 H2O cytochrome c oxidase complex ADP + Pi ATP H+ But what “pulls” the electrons down the ETC? O2 By Kim Foglia, Divison Ave. H.S., Levittown, N.Y. Modified by K. Crawford AP/IB Biology oxidative phosphorylation Electrons flow downhill Electrons move in steps from carrier to carrier downhill to O2 Each carrier more electronegative Controlled oxidation Controlled release of energy By Kim Foglia, Divison Ave. H.S., Levittown, N.Y. Modified by K. Crawford AP/IB Biology “proton-motive” force H+ H+ Set up a H+ H+ gradient Allow the protons to flow through ATP synthase Synthesizes ATP ADP + Pi ATP H+ H+ H+ H+ H+ ADP + Pi ATP By Kim Foglia, Divison Ave. H.S., Levittown, N.Y. Modified by K. Crawford AP/IB Biology H+ 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 By Kim Foglia, Divison Ave. H.S., Levittown, N.Y. Modified by K. Crawford AP/IB Biology Chemiosmosis By Kim Foglia, Divison Ave. H.S., Levittown, N.Y. Modified by K. Crawford AP/IB Biology 1961 | 1978 Peter Mitchell Proposed chemiosmotic hypothesis Revolutionary idea at the time proton motive force 1920-1992 By Kim Foglia, Divison Ave. H.S., Levittown, N.Y. Modified by K. Crawford AP/IB Biology Pyruvate from cytoplasm Inner + mitochondrial H membrane H+ Intermembrane space Electron transport C system Q NADH Acetyl-CoA 2. Electrons provide energy 1. Electrons are harvested to pump protons and carried to the transport across the system. membrane. - NADH Krebs cycle e- e FADH2 e- ATP e- H2O 3. Oxygen joins with protons to form water. 1 O 2 +2 2H+ O2 H+ CO2 2 H+ 32 ATP 4. Protons diffuse back in down their concentration By KimMitochondrial Foglia, Divison Ave. H.S., Levittown, N.Y. driving the gradient, matrix Modified by K. Crawford AP/IB Biologysynthesis of ATP. H+ ATP synthase Pyruvate from cytoplasm Inner + mitochondrial H membrane H+ Intermembrane space Electron transport C system Q NADH Acetyl-CoA 2. Electrons provide energy 1. Electrons are harvested to pump protons and carried to the transport across the system. membrane. - NADH Krebs cycle e- e FADH2 e- ATP e- H2O 3. Oxygen joins with protons to form water. 1 O 2 +2 2H+ O2 H+ CO2 2 H+ 32 ATP 4. Protons diffuse back in down their concentration By KimMitochondrial Foglia, Divison Ave. H.S., Levittown, N.Y. driving the gradient, matrix Modified by K. Crawford AP/IB Biologysynthesis of ATP. H+ ATP synthase Cellular respiration 2 ATP + ~2 ATP + 2 ATP + ~34 ATP By Kim Foglia, Divison Ave. H.S., Levittown, N.Y. Modified by K. Crawford AP/IB Biology 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? By Kim Foglia, Divison Ave. H.S., Levittown, N.Y. Why do we breathe? Modified by K. Crawford AP/IB Biology Taking it beyond… What is the final electron acceptor in H+ H+ H+ C Electron Transport Chain? e– NADH O2 Q e– FADH2 FAD NAD+ NADH dehydrogenase e– 2H+ + cytochrome bc complex 1 2 O2 H2O cytochrome c oxidase complex 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! By Kim Foglia, Divison Ave. H.S., Levittown, N.Y. Modified by K. Crawford AP/IB Biology What’s the point? The point is to make ATP! ATP By Kim Foglia, Division Ave. H.S., Levittown, N.Y. Modified by K. Crawford AP/IB Biology 2008-2009