Cellular Respiration Stage 4 Electron Transport Chain AP

Cellular Respiration Stage 4: Electron Transport Chain AP Biology 2006 -2007

Cellular respiration AP Biology

What’s the point? The point is to make ATP! ATP AP Biology

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! AP Biology A working muscle recycles over 10 million ATPs per second

There is a better way! § Electron Transport Chain u 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 u yields ~36 ATP from 1 glucose! u only in presence of O 2 (aerobic respiration) u AP Biology That sounds more like it! O 2

Mitochondria § Double membrane outer membrane u inner membrane u § highly folded cristae § enzymes & transport proteins u intermembrane space § fluid-filled space between membranes AP Biology Oooooh! Form fits function!

Electron Transport Chain Inner mitochondrial membrane Intermembrane space C Q NADH dehydrogenase cytochrome bc complex Mitochondrial matrix AP Biology cytochrome c oxidase complex

Remember the Electron Carriers? Glycolysis 2 NADH Time to break open the piggybank! AP Biology glucose Krebs cycle G 3 P 8 NADH 2 FADH 2

Electron Transport Chain Building proton gradient! NADH NAD+ + H e p intermembrane space H+ H+ H e- + H+ C e– NADH H FADH 2 NAD+ NADH dehydrogenase inner mitochondrial membrane e– Q AP Biology H+ e– H FAD 2 H+ + cytochrome bc complex 1 2 O 2 H 2 O cytochrome c oxidase complex mitochondrial matrix What powers the proton (H+) pumps? …

Stripping H from Electron Carriers § Electron carriers pass electrons & H+ to ETC u u H cleaved off NADH & FADH 2 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 u transport proteins in membrane pump H+ (protons) across inner membrane to intermembrane space + H H+ TA-DA!! Moving electrons do the work! + H H+ H+ H+ H H+ C e– NADH AP Biology + H H+ H+ Q e– FADH 2 FAD NAD+ NADH dehydrogenase e– 2 H+ cytochrome bc complex + 1 2 O 2 H 2 O cytochrome c oxidase complex ADP + Pi ATP H+

But what “pulls” the electrons down the ETC? H 2 O O 2 AP Biology electrons flow downhill to O 2 oxidative phosphorylation

Electrons flow downhill § Electrons move in steps from carrier to carrier downhill to oxygen each carrier more electronegative u controlled oxidation u controlled release of energy u make ATP instead of fire! AP Biology

“proton-motive” force We did it! § Set up a H+ § § H+ H+ gradient Allow the protons to flow through ATP synthase Synthesizes ATP ADP + Pi ATP Are we there yet? AP Biology H+ H+ H+ ADP + Pi ATP H+

Chemiosmosis § The diffusion of ions across a membrane u 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

1961 | 1978 Peter Mitchell § Proposed chemiosmotic hypothesis u revolutionary idea at the time proton motive force 1920 -1992 AP Biology

Pyruvate from cytoplasm Inner + mitochondrial H membrane H+ Intermembrane space Electron transport C system Q NADH Acetyl-Co. A 1. Electrons are harvested and carried to the transport system. NADH Krebs cycle e- e- FADH 2 e- 2. Electrons provide energy to pump protons across the membrane. e- H 2 O 3. Oxygen joins with protons to form water. 1 O 2 +2 2 H+ O 2 H+ CO 2 ATP Mitochondrial matrix AP Biology H+ ATP 4. Protons diffuse back in down their concentration gradient, driving the synthesis of ATP. H+ ATP synthase

~4 0 A Cellular respiration 2 ATP AP Biology + 2 ATP + ~36 ATP TP

Summary of cellular respiration C 6 H 12 O 6 + 6 O 2 § § § § 6 CO 2 + 6 H 2 O + ~40 ATP Where did the glucose come from? Where did the O 2 come from? Where did the CO 2 go? Where did the H 2 O 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

Taking it beyond… § What is the final electron acceptor in H+ H+ H+ C Electron Transport Chain? e– O 2 NADH Q e– FADH 2 FAD NAD+ NADH dehydrogenase e– 2 H+ + cytochrome bc complex 1 2 O 2 H 2 O cytochrome c oxidase complex § So what happens if O 2 unavailable? § ETC backs up nothing to pull electrons down chain u NADH & FADH 2 can’t unload H u AP Biology § ATP production ceases § cells run out of energy § and you die!

What’s the point? The point is to make ATP! ATP AP Biology