ellular Respiration Stage 4: Electron Transport hain 2006-2007 ellular respiration What s the point? The point is to make! 2006-2007 1
accounting so far Glycolysis 2 Kreb s cycle 2 Life takes a lot of energy to run, need to extract more energy than 4! There s got to be a better way! I need a lot more! A working muscle recycles over 10 million s per second There is a better way! Electron Transport hain u series of proteins built into inner mitochondrial membrane along cristae transport proteins & enzymes u transport of electrons down ET linked to pumping of to create gradient u yields ~36 from 1 glucose! u only in presence of O 2 (aerobic respiration) That sounds more like it! O 2 Mitochondria Double membrane u outer membrane u inner membrane highly folded cristae enzymes & transport proteins u intermembrane space fluid-filled space between membranes Oooooh! Form fits function! 2
Electron Transport hain Intermembrane space Inner mitochondrial membrane Q dehydrogenase Mitochondrial matrix cytochrome bc complex cytochrome c oxidase complex Remember the Electron arriers? Glycolysis glucose G3P Krebs cycle 2 8 2 FADH 2 Time to break open the piggybank! Electron Transport hain NAD + + H e p H e- + Q FADH 2 H NAD + dehydrogenase H FAD Building proton gradient! cytochrome bc complex 2 + O 2 intermembrane space inner mitochondrial membrane 1 2 H 2 O cytochrome c oxidase complex mitochondrial matrix What powers the proton ( ) pumps? 3
Stripping H from Electron arriers Electron carriers pass electrons & to ET u H cleaved off & FADH 2 u electrons stripped from H atoms (protons) electrons passed from one electron carrier to next in mitochondrial membrane (ET) flowing electrons = energy to do work u transport proteins in membrane pump (protons) across inner membrane to intermembrane space H TA-DA!! + H+ H+ Moving electrons do the work! Q FADH2 FAD ADP NAD + 2 1 + 2 O2 H2O + Pi cytochrome cytochrome c dehydrogenase bc complex oxidase complex But what pulls the electrons down the ET? O 2 H 2 O electrons flow downhill to O 2 oxidative phosphorylation Electrons flow downhill Electrons move in steps from carrier to carrier downhill to oxygen u each carrier more electronegative u controlled oxidation u controlled release of energy make instead of fire! 4
We did it! Set up a gradient Allow the protons to flow through synthase Synthesizes ADP + P i ADP + P i proton-motive force Are we there yet? hemiosmosis The diffusion of ions across a membrane u build up of proton gradient just so H+ could flow through synthase enzyme to build hemiosmosis links the Electron Transport hain to synthesis So that s the point! 1961 1978 Peter Mitchell Proposed chemiosmotic hypothesis u revolutionary idea at the time proton motive force 1920-1992 5
Pyruvate from cytoplasm Inner mitochondrial membrane Q Intermembrane space Electron transport system 1. Electrons are harvested Acetyl-oA and carried to the transport system. e - Krebs cycle O 2 e - FADH 2 e - 3. Oxygen joins with protons to form water. 2. Electrons provide energy to pump protons across the membrane. H 2 O 1 O 2 2 + 2 e - O 2 Mitochondrial matrix 4. Protons diffuse back in down their concentration gradient, driving the synthesis of. synthase ellular respiration + + 2 2 ~36 Summary of cellular respiration 6 H 12 O 6 + 6O 2 6O 2 + 6H 2 O + ~40 Where did the glucose come from? Where did the O 2 come from? Where did the O 2 come from? Where did the O 2 go? Where did the H 2 O come from? Where did the come from? What else is produced that is not listed in this equation? Why do we breathe? 6
Taking it beyond What is the final electron acceptor in Q Electron Transport hain? FADH2 FAD NAD O + cytochrome dehydrogenase bc complex 2 So what happens if O 2 unavailable? ET backs up 2 1 + 2 O2 H2O cytochrome c oxidase complex u nothing to pull electrons down chain u & FADH 2 can t unload H production ceases cells run out of energy and you die! What s the point? The point is to make! 2006-2007 7