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Cellular Respiration: Electron Transport Chain Ch. 9

Cellular Respiration: Electron Transport Chain Ch. 9. Ms. Springstroh AP Biology Adapted from Ms. Gaynor-Day and Mr. Grant. What’s the point?. The point is to make ATP !. ATP. ATP accounting so far…. Glycolysis  2 ATP Kreb’s cycle  2 ATP

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Cellular Respiration: Electron Transport Chain Ch. 9

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  1. Cellular Respiration: Electron Transport ChainCh. 9 Ms. Springstroh AP Biology Adapted from Ms. Gaynor-Day and Mr. Grant

  2. What’s thepoint? The pointis to makeATP! ATP

  3. ATP accounting so far… • Glycolysis 2ATP • Kreb’s cycle 2ATP • 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 lotmore ATP! A working muscle recycles over 10 million ATPs per second

  4. Stage #3: Oxidative Phosphorylation(Electron Transport Chain (ETC) + Chemiosmosis) • Chemiosmosisis a process which connects the processes of electron transport and ATP synthesis • NADH and FADH2 • Drop off e-’s at ETC, which powers ATP synthesis using oxidative phosphorylation **OCUURS IN CRISTAE (folds of inner membrane)

  5. Mitochondria • Double membrane • outer membrane • inner membrane • highly folded cristae • enzymes & transport proteins • intermembrane space • fluid-filled space between membranes Oooooh!Form fits function!

  6. What is “oxidative phosphorylation”? • Recall… • Take H+/e-’s away, molecule = “oxidized” • Give H+/e-’s, molecule = “reduced” • Give phosphate  molecule = “phosphorylated” • So…oxidative phosphorylation= process that couples removal of H+’s/ e-’s from one molecule (NADH or FADH2) & giving phosphate molecules to another molecule (ADP)

  7. Difference between oxidative phosphorylation & substrate-level phosphorylation Oxidative phosphorylation: generates ATP when electrons are taken from NADH or FADH2 (which become oxidized) and go down the electron transport chain. This causes Pi (inorganic phosphate) to join with ADP to form ATP. Substrate-level phosphorylation: generates ATP when an enzyme takes a phosphate from a substrate molecule and gives it directly to ADP.

  8. The Pathway of Electron Transport • In the ETC… • e-’s fall from glucose to oxygen not directly, rather in a series of steps. As the e-’s fall from step to step, energy is released in manageable amounts. **NEEDS O2 TO PROCEED (unlike glycolysis)

  9. ETC Characteristics • Occurs in cristae, which increase surface area of inner mitochondrial membrane  allows more ATP to be produced • ETC takes e-’s from NADH/FADH2and gives them toO2 • O2 “pulls” e-’s “down” ETC due to electronegativity (high affinity for e-’s)

  10. What happens at the end of the ETC chain? • Electrons are passed to oxygen, forming water • O2 = final e- acceptor

  11. How ETC generates ATP • ETC does NOT make ATP directly but provides the stage for chemiosmosis to occur • The energy from “falling” e-’s (exergonic) in the ETC is used to pump H+’s from mitochondrial matrix to intermembranespace • Results in a H+ (proton) gradientinside mitochondria • Inside (matrix) = low [H+] • Outside (intermembrane space) = high [H+]

  12. http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120071/bio11.swf::Electron%20Transport%20System%20and%20ATP%20Synthesishttp://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120071/bio11.swf::Electron%20Transport%20System%20and%20ATP%20Synthesis Inner Mitochondrial membrane Oxidative phosphorylation. electron transport and chemiosmosis Glycolysis ATP ATP ATP H+ H+ H+ H+ Cyt c Protein complex of electron carriers Intermembrane space Q IV I III ATP synthase II Inner mitochondrial membrane H2O FADH2 2 H+ + 1/2 O2 FAD+ NADH+ NAD+ ATP ADP + P i (Carrying electrons from, food) H+ Mitochondrial matrix Chemiosmosis ATP synthesis powered by the flow Of H+ back across the membrane Electron transport chain Electron transport and pumping of protons (H+), which create an H+ gradient across the membrane Oxidativephosphorylation Figure 9.15 • Chemiosmosis and the electron transport chain

  13. Chemiosmosis • Utilizes ATP synthase • the enzyme that actually makes ATP from ADP and Pi • A mechanism which uses energy stored in the H+ gradient across any membrane to drive cellular work • Cellular work in this case = synthesis of ATP

  14. INTERMEMBRANE SPACE H+ H+ H+ H+ H+ H+ H+ H+ ADP + ATP P i MITOCHONDRIAL MATRIX Figure 9.14 Chemiosmosis: The Energy-Coupling Mechanism ATP Synthase

  15. Electron shuttles span membrane MITOCHONDRION CYTOSOL 2 NADH or 2 FADH2 2 FADH2 2 NADH 2 NADH 6 NADH Glycolysis Oxidative phosphorylation: electron transport and chemiosmosis Citric acid cycle 2 Acetyl CoA 2 Pyruvate Glucose + 2 ATP + about 32 or 34 ATP by substrate-level phosphorylation by substrate-level phosphorylation by oxidative phosphorylation About 36 or 38 ATP Maximum per glucose: Figure 9.16 • There are three main processes in this metabolic enterprise + 2 ATP

  16. We will cover the following two slides when we learn about photosynthesis, but you can preview them now if you want. You’ll probably understand most of them!

  17. A Comparison of Chemiosmosis in Chloroplasts and Mitochondria • Chloroplasts and mitochondria • Generate ATP by the SAME basic mechanism: chemiosmosis • But use different sources of energy to accomplish this • http://student.ccbcmd.edu/~gkaiser/biotutorials/cellresp/atpase_flash.html

  18. The spatial organization of chemiosmosis differs in chloroplasts and mitochondria • In both organelles • electron transport chains generate a H+ gradient across a membrane • ATP synthase • Uses this proton-motive force to make ATP

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