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Cellular Respiration: Harvesting Chemical Energy

Cellular Respiration: Harvesting Chemical Energy. Chapter 9. Oxidation/Reduction. What is an oxidation reaction? Where electrons are lost What is a reduction reaction? Where electrons are gained What is happening in a Redox reaction?

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Cellular Respiration: Harvesting Chemical Energy

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  1. Cellular Respiration: Harvesting Chemical Energy Chapter 9

  2. Oxidation/Reduction • What is an oxidation reaction? • Where electrons are lost • What is a reduction reaction? • Where electrons are gained • What is happening in a Redox reaction? • One substance loses an electron(s) and the other gains the electron(s)

  3. Respiration • What is being oxidized in cellular respiration? • Glucose, since it will lose electrons. • What does glucose become once it is oxidized? • Carbon dioxide • What is being reduced? • Oxygen, since ultimately it will gain the electrons • What does reduced oxygen become? • Water

  4. Oxidizing Agent • The oxidizing agent is the recipient of the electrons and therefore is the agent responsible for the oxidation • Why doesn’t the oxidation of glucose occur in one single step? • It would be too explosive and not enough energy would be harnessed • There are other oxidizing agents for respiration besides oxygen

  5. What is the oxidizing agent here?

  6. What is the oxidizing agent here? NAD+

  7. How is energy transferred? • It is important to see that there is a change in the covalent status of electrons as they are transferred throughout respiration • The electrons begin the journey in an unstable configuration and end in a stable molecule

  8. Glycolysis What does the hexokinase enzyme do?

  9. Why would the cell invest ATP, when it is attempting to make more ATP’s?

  10. What would the phosphofructokinase do?

  11. So far how many ATP’s have been invested?

  12. What does the dehydrogenase enzyme do?

  13. What method is used here to generate ATP?

  14. Removal of water rearranges substrate electrons and makes remaining P bond unstable What does pyruvate kinase do?

  15. Substrate Level Phosphorylation ATP made by direct transfer of a phosphate group from an organic substrate to ADP by an enzyme

  16. Energy Input and Output of Glycolysis

  17. The oxidizing agent of Glycolysis • What is the oxidizing agent of glycolysis? • NAD+ • Without NAD+ glycolysis cannot continue • Is glycolysis anaerobic or aerobic? • It is anaerobic, does not require oxygen

  18. Formation of Acetyl CoA

  19. Total Energy Yield So Far • From Glycolysis: • 2 ATP’s and 2 NADH’s • From Pyruvate - Acetyl CoA : • 2 NADH’s • From Krebs Cycle: • 2 ATP’s, 6 NADH’s, and 2 FADH2’s • Where is all of the energy?

  20. IT IS ALL LOCKED IN THE NADH’S AND THE FADH2’S!

  21. So far the ATP’s have been generated via substrate level phosphorylation, now it’s time for chemiosmosis

  22. The Electron Transport Chain • What is the ETC? Where is it located? • It is a series of electron carrier molecules, that transfer electrons to each other through a connected series of redox reactions • It is located within the inner membrane of the mitochondrion

  23. What is the role of oxygen? • The highly electronegative oxygen is the only molecule capable of receiving the stable electron from cytochrome a3. • The cytochrome electron carriers are proteins with heme prosthetic group • The iron of the cytochromes transfers electrons

  24. Chemiosmosis and ETC coupled to ATP synthesis

  25. Overview of Cellular Respiration

  26. The Final Count • For every NADH produced in the mitochondrion, how many ATP’s are created via oxidative phosphorylation? • 3 • For every FADH2 produced, how many ATP’s are created via oxidative phosphorylation? • 2 • For the 2 NADH’s generated in glycolysis how many ATP’s are created? • 2

  27. 2 NADH’s from glycolysis ---->4-6 ATP’s • 8 NADH’s from the mitochondrial matrix ----> 24 ATP’s • 2 FADH2’s from KC -----> 4 ATP’s • Total ATP’s from oxidative phosphorylation = 32 ATP’s • ATP’s from substrate level phosphorylation = 4 • GRAND TOTAL = 36- 38 ATP’s

  28. Efficiency of Respiration • The total G for the combustion of glucose = -686 kcal/mol. • Phosphorylation of ADP to ATP stores approximately 7.3 kcal/mole • Respiration efficiency is 7.3 x 38 = 277.4 kcal/mole • 40% use of available energy is used • A car can use only 25% of energy stored in gasoline • Where does the rest of the energy go?

  29. Variables in ATP yield • Some mitochondria differ in permeability to protons, which effects the proton motive force • Proton motive force may be directed to drive other cellular processes such as active transport • ATP yield is inflated by rounding up • Prokaryotic cellular respiration is slightly higher since no mitochondrial membrane used to transport electrons from NADH

  30. Poisons • Rotenone blocks the first electron carrier, used to poison fish, and insects • Cyanide and carbon monoxide block cyt a3, so what will the symptoms be? • Oligomycin - physically blocks the passage of H+ through ATP synthase. It is used on skin to combat fungal infections. • Uncouplers such as dinitrophenol, makes membrane leaky to H+

  31. How does glycolysis proceed in the absence of oxygen? • What is the oxidizing agent of glycolysis? • NAD+ • How is NAD+regenerated so that glycolysis can continue? • Through the ETC • How is NAD+regenerated in the absence of ETC (no oxygen)?

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