AP Biology - TeacherWeb
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AP Biology Cellular respiration Cellular Respiration Stage 4: Electron Transport Chain AP Biology 2006-2007 AP Biology ATP accounting so far… Glycolysis → 2 ATP Kreb’s cycle → 2 ATP Life takes a lot of energy to run, need to What’s the point? The p point is to make extract more energy gy than 4 ATP! There’s got to be a better way! ATP! I need a lot more ATP! ATP AP Biology 2006-2007 AP Biology A working muscle recycles over 10 million ATPs per second 1 AP Biology There is a better way! Electron Transport Chain Mitochondria Double membrane series of proteins built into ___________________________________ along cristae highly folded cristae transport t t proteins t i & enzymes enzymes & transport proteins transport of electrons down ETC linked to pumping of H+ to create H+ gradient yields ___________ from 1 glucose! only in presence of O2 (_________________) AP Biology outer membrane ____________________ That sounds more like it! ____________________ fluid-filled space between membranes O2 AP Biology Electron Transport Chain Remember the Electron Carriers? Inner mitochondrial membrane Intermembrane space Oooooh! Form fits function! Glycolysis glucose Krebs cycle G3P 2 NADH C 8 NADH 2 FADH2 Q Time to break open the piggybank! NADH dehydrogenase cytochrome bc complex cytochrome c oxidase complex Mitochondrial matrix AP Biology AP Biology 2 AP Biology Electron Transport Chain NADH → NAD+ +H intermembrane space e p H → e- + Building proton gradient! H+ H+ H+ C e– NADH H FADH2 e– FAD 2H+ + cytochrome bc complex 1 2 O2 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 H NAD+ NADH dehydrogenase inner mitochondrial membrane e– Q AP Biology H+ Stripping H from Electron Carriers Electron carriers pass electrons & H+ to ETC H2 O cytochrome c oxidase complex mitochondrial matrix What powers the proton (H+) pumps?… But what “pulls” the electrons down the ETC? transport proteins in membrane pump H+ (protons) across inner membrane to intermembrane space H+ TA-DA!! Moving electrons do the work! H+ H+ H+ H+ H+ H+ + H+ H H+ C e– NADH AP Biology H+ Q e– FADH2 FAD NAD+ NADH dehydrogenase e– 2H+ + cytochrome bc complex 1 2 O2 H2O cytochrome c oxidase complex ADP + Pi ATP H+ Electrons flow downhill Electrons move in steps from carrier to carrier downhill to ___________ each carrier more electronegative controlled oxidation controlled release of energy O2 AP Biology electrons flow downhill to O2 oxidative phosphorylation make ATP instead of fire! AP Biology 3 AP Biology “proton-motive” force We did it! Set up a H+ H+ H+ H+ gradient Allow the protons to flow through ATP synthase Synthesizes ATP ADP + Pi → ATP Are we there yet? H+ H+ H+ H+ H+ Chemiosmosis __________________________________________ build up of proton gradient just so H+ could flow through ATP synthase enzyme to build ATP _______________ links the Electron Transport Chain to ATP synthesis ADP + Pi ATP So that’s the point! H+ AP Biology AP Biology 1961 | 1978 Peter Mitchell Proposed chemiosmotic hypothesis Pyruvate from cytoplasm Inner mitochondrial H+ membrane revolutionary idea at the time H+ Intermembrane space Electron transport C system Q NADH Acetyl-CoA Acetyl CoA 2. Electrons eprovide energy 1. Electrons are harvested to pump protons and carried to the transport across the system. membrane. - NADH Krebs cycle proton motive force ATP 1920-1992 Mitochondrial matrix AP Biology H2O e- 3. Oxygen joins 1 O 2 +2 2H+ with protons to form water. O2 H+ CO2 2 AP Biology e FADH2 H+ e- 32 ATP 4. Protons diffuse back in down their concentration gradient, driving the synthesis of ATP. H+ ATP synthase 4 AP Biology Cellular respiration Summary of cellular respiration C6H12O6 + 6O2 → 6CO2 + 6H2O + ~40 ATP + 2 ATP 2 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 ~36 ATP AP Biology Taking it beyond… What is the final electron acceptor in H+ H+ H+ What’s the point? C Q Electron Transport Chain?e – NADH O2 FADH2 NAD+ NADH dehydrogenase e– e– FAD 2H+ + cytochrome bc complex 1 2 O2 H2O cytochrome c oxidase complex The p point is to make So what happens if O2 unavailable? ETC backs up ATP! nothing to pull electrons down chain NADH & FADH2 can’t unload H AP Biology ATP production ceases cells run out of energy and you die! ATP AP Biology 5