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Chapter 9


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Chapter 9

  1. 1. Chapter 9~ Cellular Respiration: <ul><li>Harvesting Chemical Energy </li></ul>
  2. 2. Cells need energy to perform cellular work: <ul><li>Growth </li></ul><ul><li>Metabolism </li></ul><ul><li>Movement </li></ul><ul><li>Contraction </li></ul><ul><li>Cell division </li></ul><ul><li>Transport </li></ul>
  3. 3. Principles of Energy Harvesting <ul><li>Respiration is a Catabolic pathway </li></ul><ul><li>Organic compounds such as glucose are broken down releasing the energy stored in the chemical bonds </li></ul>
  4. 5. Cellular Respiration <ul><li>C 6 H 12 O 6 + 6O 2 ---> 6CO 2 + 6H 2 O + </li></ul>ATP
  5. 6. Cellular respiration has 3 components: <ul><li>Glycolysis: occurs in the cytosol; degrades glucose into pyruvate </li></ul><ul><li>Kreb’s Cycle: occurs in mitochondrial matrix; pyruvate into carbon dioxide </li></ul><ul><li>Electron Transport Chain: occurs in inner membrane of mitochondrion; electrons passed to oxygen </li></ul>
  6. 8. Respiration is a Redox reaction <ul><li>Oxidation-reduction </li></ul><ul><li>Oxidation is e-loss; reduction is e-gain </li></ul><ul><li>Reducing agent: e-donor </li></ul><ul><li>Oxidizing agent: e-acceptor </li></ul>
  7. 9. “ Leo says Ger”
  8. 10. <ul><li>Na + Cl Na+ + Cl- </li></ul><ul><li>Sodium is ______________? </li></ul><ul><li>Chlorine is _____________? </li></ul>
  9. 11. Some redox reactions change the degree of sharing between covalent bonds
  10. 12. <ul><li>C 6 H 12 O 6 + 6O 2 ---> 6CO 2 + 6H 2 O + </li></ul>ATP
  11. 13. Oxidizing agent in respiration <ul><li>NAD+ (nicotinamide adenine dinucleotide) </li></ul><ul><li>Removes electrons from food (series of reactions) </li></ul><ul><li>NAD+ is reduced to NADH </li></ul><ul><li>Enzyme action: dehydrogenase </li></ul><ul><li>Oxygen is the eventual e- acceptor </li></ul>
  12. 15. Glycolysis <ul><li>1 Glucose 2 pyruvate molecules </li></ul><ul><li>C 6 2C 3 molecules </li></ul>
  13. 16. <ul><li>Energy investment phase : cell uses ATP to phosphorylate fuel </li></ul><ul><li>Energy payoff phase : ATP is produced by substrate-level phosphorylation and NAD+ is reduced to NADH by food oxidation </li></ul><ul><li>Net energy yield per glucose molecule : 2 ATP plus 2 NADH; no CO2 is released. </li></ul>
  14. 18. Other compounds can be converted to simple sugars and consumed during glycolysis <ul><li>Proteins are hydrolyzed into amino acids </li></ul><ul><li>Fats are digested into glycerol and fatty acids </li></ul>
  15. 19. Krebs Cycle (Citric Acid Cycle) <ul><li>Completes the energy yielding oxidation of organic molecules </li></ul>
  16. 20. If molecular oxygen is present……. <ul><li>Each pyruvate is converted into acetyl CoA (begin w/ 2): </li></ul><ul><ul><li>CO2 is released; </li></ul></ul><ul><ul><li>NAD+ ---> NADH; </li></ul></ul><ul><ul><li>coenzyme A (from B vitamin), makes molecule very reactive </li></ul></ul>
  17. 21. For each pyruvate that enters: <ul><li>3 NAD+ reduced to NADH </li></ul><ul><li>1 FAD+ reduced to FADH 2 </li></ul><ul><li>1 ATP molecule </li></ul>
  18. 23. Electron Transport Chains <ul><li>Couple electron transport (exergonic) to ATP synthesis (endergonic) </li></ul><ul><li>Oxygen is the terminal (final) electron receptor, therefore the process produces ATP by “Oxidative Phosphorylation” </li></ul><ul><li>Produces 32-34 molecules of ATP per molecule of glucose </li></ul>
  19. 24. Electron transport chains <ul><li>Involve electron carrier molecules (membrane proteins) </li></ul><ul><li>Shuttle electrons that release energy used to make ATP </li></ul><ul><li>Sequence of reactions that prevents energy release in 1 explosive step </li></ul>
  20. 26. Electron route: <ul><li>food </li></ul><ul><li>NADH </li></ul><ul><li>electron transport chain </li></ul><ul><li>oxygen </li></ul>
  21. 27. Electron transport chain <ul><li>Cytochromes carry electron carrier molecules (NADH & FADH2) down to oxygen </li></ul><ul><li>Chemiosmosis : energy coupling mechanism </li></ul><ul><li>ATP synthase : produces ATP by using the H+ gradient (proton-motive force) pumped into the inner membrane space from the electron transport chain; this enzyme harnesses the flow of H+ back into the matrix to phosphorylate ADP to ATP (oxidative phosphorylation) </li></ul>
  22. 30. Review: Cellular Respiration <ul><li>Glycolysis: 2 ATP (substrate-level phosphorylation) </li></ul><ul><li>Kreb’s Cycle: 2 ATP (substrate-level phosphorylation) </li></ul><ul><li>Electron transport & oxidative phosphorylation: 2 NADH (glycolysis) = 6ATP 2 NADH (acetyl CoA) = 6ATP 6 NADH (Kreb’s) = 18 ATP 2 FADH2 (Kreb’s) = 4 ATP </li></ul><ul><li>38 TOTAL ATP/glucose </li></ul>
  23. 31. FERMENTATION <ul><li>When oxygen is not available, glycolysis is followed by : </li></ul><ul><ul><li>Alcohol fermentation </li></ul></ul><ul><ul><ul><li>pyruvate to ethanol </li></ul></ul></ul><ul><ul><li>lactic acid fermentation </li></ul></ul><ul><ul><ul><li>pyruvate to lactate </li></ul></ul></ul><ul><ul><ul><li>Occurs in muscle of animals when insufficient oxygen is present </li></ul></ul></ul>
  24. 32. Fermentation <ul><li>Does not produce any additional ATP </li></ul><ul><li>Does regenerate oxidized NAD, to keep glycolysis operating </li></ul>