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Cellular Catabolism The Electron Transport Chain & Oxidative Phosphorylation

Cellular Catabolism The Electron Transport Chain & Oxidative Phosphorylation. Packet #28 Chapter #9. Summary Thus Far…. At the end of the Krebs Cycle, and before the cell makes more ATP at the electron transport chain, produced so far is… 2 NET ATP Glycolysis 2 GTP Kreb’s Cycle

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Cellular Catabolism The Electron Transport Chain & Oxidative Phosphorylation

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  1. Cellular CatabolismThe Electron Transport Chain & Oxidative Phosphorylation Packet #28 Chapter #9

  2. Summary Thus Far… • At the end of the Krebs Cycle, and before the cell makes more ATP at the electron transport chain, produced so far is… • 2 NET ATP • Glycolysis • 2 GTP • Kreb’s Cycle • Later changed to ATP • 2 FADH • Kreb’s Cycle • 10 NADH • 2 from Glycolysis • See upcoming slides. • 2 as pyruvate is changed to ACoA • 6 from the Kreb’s Cycle • 6 CO2 • 4 from the Kreb’s Cycle • 2 as pyruvate is changed to ACoA

  3. Oxidative Phosphorylation & Chemiosmosis

  4. Oxidative Phosphorylation vs. Chemiosmosis • Oxidative Phosphorylation • Process in mitochondria in which ATP formation is driven by the transfer of electrons from food molecules to oxygen. • The ultimate destination of the electrons, that originated with the food molecule (glucose), is oxygen. • This oxygen atom is combined with H+ ions to make H2O. • More to come later

  5. Oxidative Phosphorylation vs. Chemiosmosis II • Chemiosmosis • Also known as chemiosmotic coupling • This is the mechanism in which a gradient of hydrogen ions (a pH gradient), across the inner mitochondria membrane, is used to drive an energy requiring process. • Examples • ATP production at the electron transport chain • The transport of a molecule across a membrane. • Flashback to previous packet. • Co-transport

  6. Oxidative Phosphorylation vs. Chemiosmosis III • What is the connection between Oxidative Phosphorylation and Chemiosmosis? • In order for oxidative phosphorylation to occur, chemiosmosisMUST be part of the process.

  7. The Goal of the Electron Transport Chain

  8. Goal of the Electron Transport Chain I • The function of the electron transport chain is to convert all of the previously made NADH and FADH into ATP. • This happens via oxidative phosphorylation. • The electron transport chain is located in the inner membrane of the mitochondria and is composed of 5 complexes • Electron carriers and ATP synthase. • The complexes, of the electron transport chain, are used to produce large amounts of ATP

  9. Yields of ATP • 1 FADH produces 2 ATP’s • 1 NADH produces 3 ATP’s • However, one must be mindful of what happens to the NADH entering into the mitochondria after glycolysis has occurred.

  10. NADH, Glycolysis & The Electron Transport Chain • Remember that glycolysis occurs in the cytosol of the cell. • The NADH produced is in the cytosol of the cell. • The NADH produced in the cytosol of the cell must enter the mitochondria via shuttles.

  11. NADH, Glycolysis & The Electron Transport Chain II • There are TWO types of shuttles used for moving the NADH produced in the cytosol into the mitochondria matrix. • Glycerophosphate shuttle • Changes NADH into FADH as it transported into the mitochondria • Malate-aspartate shuttle • NADH remains as NADH as it transported into the mitochondria

  12. ATP Synthase • As the hydrogen ions, resulting from the change of NADH to NAD+, are pumped across ATP synthase (Complex #5), ADP & P are changed into ATP.

  13. Oxidative Phosphorylation at the Electron Transport Chain

  14. Oxidative Phosphorylation at the Electron Transport Chain

  15. Calculating the Total Amount of ATP’s per Glucose molecule

  16. The Big Picture

  17. Calculating the Total Amount of ATP’s per Glucose Molecule • Glycolysis • 2 net ATP • substrate level phosphorylation—chemical reactions • 4-6 ATP (2 NADH) (Shuttles) • Pyruvate to ACOA • 6 ATP (2 NADH) • Krebs Cycle • 2 ATP • From 2 GTP’s • 18 ATP (6 NADH) • 4 ATP (2 FADH) • In the end we have a total of 36-38 net ATPs generated.

  18. Drugs that Impact the Production of ATP

  19. Drugs That Impact the Production of ATP at the Electron Transport Chain • Oligomycin • Drug that binds to the stalk of ATP synthase and closes the H channel • 2, 4-dinitrophenol • This is an uncoupler • These increase the permeability of the inner mitochondrial membrane to protons • Causes electron transport to proceed at a rapid rate without the establishment of a gradient • The energy produced by the transport of electrons is released as heat rather than being used to synthesize ATP • Fever • Aspirin is an uncoupler • This is what explains fevers with overdoses

  20. Review I

  21. Review II

  22. Regulation of Glycolysis/Cell Respiration

  23. Regulation of Glycolysis/Cell Respiration • Regulation is via allosteric activation or inhibition or via the phosphorylation or dephosphorylation of rate-limiting enzymes. • Phosphofructokinase is inhibited by ATP and activated by AMP • Enzyme used to make fructose 1, 6 bisphosphate • Inhibition by citrate • First intermediate of the Kreb’s Cycle

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