ellular respiration ellular Respiration Stage 4: Electron Transport hain What s the point? The point is to make! accounting so far Glycolysis 2 Kreb s cycle 2 Life takes a lot of energy to run, need to extract more energy than 4! I need a lot more Than that! There s got to be a better way! A working muscle recycles over 10 million s per second 1
There is a better way! Electron Transport hain series of proteins built into inner mitochondrial membrane along cristae transport proteins & enzymes transport of electrons down ET linked to pumping of to create gradient yields ~36 from 1 glucose! only in presence of O 2 (aerobic respiration) Mitochondria Double membrane outer membrane inner membrane highly folded cristae enzymes & transport proteins intermembrane space fluid-filled space between membranes That sounds more like it!! O 2 Oooooh! Form fits function! Electron Transport hain Intermembrane space Inner mitochondrial membrane Remember the Electron arriers? Glycolysis glucose Krebs cycle G3P 2 8 2 FADH 2 dehydrogenase Mitochondrial matrix cytochrome bc complex cytochrome c oxidase complex Time to break open the piggybank! 2
Electron Transport hain NAD + + H e p H e- + FADH 2 H NAD + dehydrogenase H FAD Building proton gradient! cytochrome bc complex intermembrane space inner mitochondrial membrane 1 2 H 2 O cytochrome c oxidase complex mitochondrial matrix 2 + O 2 Stripping H from Electron arriers Electron carriers pass electrons & to ET H cleaved off & FADH 2 electrons stripped from H atoms (protons) electrons passed from one electron carrier to next in mitochondrial membrane (ET) flowing electrons = energy to do work transport proteins in membrane pump (protons) across inner membrane to intermembrane space TA-DA!! Moving electrons do the work! FAD NAD + 2 1 + 2 O 2 H 2O FADH 2 cytochrome cytochrome c dehydrogenase bc complex oxidase complex H+ What powers the proton ( ) pumps? ADP + P i H+ But what pulls the electrons down the ET? Electrons flow downhill Electrons move in steps from carrier to carrier downhill to oxygen each carrier more electronegative controlled oxidation controlled release of energy O 2 H 2 O make instead of fire! electrons flow downhill to O 2 oxidative phosphorylation 3
We did it! Set up a gradient Allow the protons to flow through synthase Synthesizes ADP + P i Are we there yet? proton-motive force ADP + P i hemiosmosis The diffusion of ions across a membrane 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! Peter Mitchell Proposed chemiosmotic hypothesis revolutionary idea at the time 1961 1978 Pyruvate from cytoplasm Inner mitochondrial membrane Intermembrane space Electron transport system proton motive force 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 1920-1992 Mitochondrial matrix 4. Protons diffuse back in down their concentration gradient, driving the synthesis of. synthase 4
ellular respiration Summary of cellular respiration 6 H 12 O 6 + 6O 2 6O 2 + 6H 2 O + ~38 2 + 2 + ~34 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? H Taking it beyond + What is the final electron e acceptor in Electron Transport FADH 2 FAD hain? NAD O + 2 1 + 2 O 2 cytochrome dehydrogenase bc complex 2 So what happens if O 2 unavailable? ET backs up nothing to pull electrons down chain & FADH 2 can t unload H production ceases cells run out of energy and you die! H 2O cytochrome c oxidase complex What s the point? The point is to make! 5
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