Chapter 9 Cellular Respiration: Harvesting Chemical Energy
<ul><li>Overview: Life Is Work </li></ul><ul><li>Living cells </li></ul><ul><ul><li>Require transfusions of energy from ou...
<ul><li>The giant panda </li></ul><ul><ul><li>Obtains energy for its cells by eating plants </li></ul></ul>Figure 9.1
<ul><li>Energy </li></ul><ul><ul><li>Flows into an ecosystem as sunlight and leaves as heat </li></ul></ul>Light energy EC...
<ul><li>Concept 9.1: Catabolic pathways yield energy by oxidizing organic fuels </li></ul><ul><li>These fuels can consists...
Catabolic Pathways and Production of ATP <ul><li>The breakdown of organic molecules is exergonic </li></ul><ul><li>All exe...
<ul><li>Cellular respiration </li></ul><ul><ul><li>Is the most prevalent and efficient catabolic pathway </li></ul></ul><u...
<ul><li>To keep working </li></ul><ul><ul><li>Cells must regenerate _______ </li></ul></ul>
Redox Reactions: Oxidation and Reduction <ul><li>Catabolic pathways yield energy </li></ul><ul><ul><li>Due to the transfer...
The Principle of Redox <ul><li>Redox reactions </li></ul><ul><ul><li>Transfer electrons from one reactant to another by ox...
<ul><li>In oxidation </li></ul><ul><ul><li>A substance loses electrons, or is oxidized </li></ul></ul><ul><li>In reduction...
<ul><li>Examples of redox reactions </li></ul>Na  +  Cl  Na +   +  Cl – becomes oxidized (loses electron) becomes reduced ...
<ul><li>Some redox reactions </li></ul><ul><ul><li>Do not completely exchange electrons </li></ul></ul><ul><ul><li>Change ...
Oxidation of Organic Fuel Molecules During Cellular Respiration <ul><li>During cellular respiration </li></ul><ul><ul><li>...
Stepwise Energy Harvest via NAD +  and the Electron Transport Chain <ul><li>Cellular respiration </li></ul><ul><ul><li>Oxi...
<ul><li>Electrons from organic compounds </li></ul><ul><ul><li>Are usually first transferred to NAD + , a coenzyme </li></...
<ul><li>NADH, the reduced form of NAD + </li></ul><ul><ul><li>Passes the electrons to the electron transport chain </li></...
<ul><li>If electron transfer is not stepwise </li></ul><ul><ul><li>A large release of energy occurs </li></ul></ul><ul><ul...
<ul><li>The electron transport chain </li></ul><ul><ul><li>Passes electrons in a series of steps instead of in one explosi...
2 H 1 / 2  O 2 (from food via NADH) 2 H +  +  2 e – 2 H + 2 e – H 2 O 1 / 2  O 2 Controlled release of energy for  synthes...
The Stages of Cellular Respiration:  A Preview <ul><li>Respiration is a cumulative function of three metabolic stages </li...
<ul><li>Anaerobic : Without Oxygen </li></ul><ul><li>Aerobic : With Oxygen </li></ul><ul><li>Glycolysis </li></ul><ul><ul>...
<ul><li>Oxidative Phosphorylation </li></ul><ul><ul><li>Is driven by the electron transport chain (ETC). </li></ul></ul><u...
<ul><li>An overview of cellular respiration </li></ul>Figure 9.6 Electrons carried via NADH Glycolsis Glucose Pyruvate ATP...
<ul><li>Both glycolysis and the citric acid cycle </li></ul><ul><ul><li>Can generate ATP by _________ level phosphorylatio...
<ul><li>Concept 9.2: Glycolysis harvests energy by oxidizing glucose to pyruvate </li></ul><ul><li>Glycolysis </li></ul><u...
<ul><li>Glycolysis consists of two major phases </li></ul><ul><ul><li>Energy investment phase </li></ul></ul><ul><ul><li>E...
Dihydroxyacetone phosphate Glyceraldehyde- 3-phosphate H H H H H OH OH HO HO CH 2 OH H H H H O H OH HO OH P CH 2 O P H O H...
2 NAD + NADH 2 + 2 H + Triose phosphate dehydrogenase 2 P  i 2 P C CHOH O P O CH 2 O 2 O – 1, 3-Bisphosphoglycerate 2 ADP ...
<ul><li>Concept 9.3: The citric acid cycle completes the energy-yielding oxidation of organic molecules </li></ul><ul><li>...
<ul><li>Before the citric acid cycle can begin </li></ul><ul><ul><li>Pyruvate must first be converted to acetyl CoA, which...
<ul><li>An overview of the citric acid cycle </li></ul>ATP 2 CO 2 3 NAD + 3 NADH + 3 H + ADP +  P   i FAD FADH 2 Citric ac...
<ul><li>A closer look at the citric acid cycle </li></ul>
Figure 9.12 Acetyl CoA NADH Oxaloacetate Citrate Malate Fumarate Succinate Succinyl CoA  -Ketoglutarate  Isocitrate Citri...
<ul><li>Concept 9.4: During oxidative phosphorylation, ____________ couples electron transport to ATP synthesis </li></ul>...
The Pathway of Electron Transport <ul><li>In the electron transport chain </li></ul><ul><ul><li>Electrons from NADH and FA...
<ul><li>At the end of the chain </li></ul><ul><ul><li>Electrons are passed to oxygen, forming water </li></ul></ul><ul><ul...
Chemiosmosis: The Energy-Coupling Mechanism <ul><li>ATP synthase </li></ul><ul><ul><li>Is the enzyme that actually makes A...
<ul><li>At certain steps along the electron transport chain (ETC) </li></ul><ul><ul><li>Electron transfer causes protein c...
<ul><li>The resulting H +  gradient </li></ul><ul><ul><li>Stores energy </li></ul></ul><ul><ul><li>Drives  chemiosmosis  i...
<ul><li>Chemiosmosis </li></ul><ul><ul><li>Is an energy-coupling mechanism that uses ________ in the form of a H +  gradie...
<ul><li>Chemiosmosis and the electron transport chain </li></ul>Oxidative phosphorylation. electron transport and chemiosm...
An Accounting of ATP Production by Cellular Respiration <ul><li>During respiration, most energy flows in this sequence </l...
<ul><li>There are three main processes in this metabolic enterprise </li></ul>Electron shuttles span membrane CYTOSOL 2 NA...
<ul><li>About 40% of the energy in a glucose molecule </li></ul><ul><ul><li>Is transferred to ATP during cellular respirat...
<ul><li>Concept 9.5: Fermentation enables some cells to produce ATP without the use of oxygen </li></ul><ul><li>Cellular r...
<ul><li>Glycolysis </li></ul><ul><ul><li>Can produce ATP with or without oxygen, in aerobic or anaerobic conditions </li><...
Types of Fermentation <ul><li>Fermentation consists of </li></ul><ul><ul><li>Glycolysis plus reactions that regenerate NAD...
<ul><li>In alcohol fermentation </li></ul><ul><ul><li>Pyruvate is converted to ethanol in two steps, one of which releases...
<ul><li>During lactic acid fermentation </li></ul><ul><ul><li>Pyruvate is reduced directly to NADH to form lactate as a wa...
2 ADP + 2 P 1 2 ATP Glycolysis Glucose 2 NAD + 2 NADH 2 Pyruvate 2 Acetaldehyde 2 Ethanol (a) Alcohol fermentation 2 ADP +...
Fermentation and Cellular Respiration Compared <ul><li>Both fermentation and cellular respiration </li></ul><ul><ul><li>Us...
<ul><li>Fermentation and cellular respiration </li></ul><ul><ul><li>Differ in their final electron acceptor </li></ul></ul...
<ul><li>Pyruvate is a key juncture in catabolism </li></ul>Glucose CYTOSOL Pyruvate No O 2  present Fermentation O 2  pres...
The Evolutionary Significance of Glycolysis <ul><li>Glycolysis </li></ul><ul><ul><li>Occurs in nearly all organisms </li><...
<ul><li>Concept 9.6: Glycolysis and the citric acid cycle connect to many other metabolic pathways </li></ul>
The Versatility of Catabolism <ul><li>Catabolic pathways </li></ul><ul><ul><li>Funnel electrons from many kinds of organic...
<ul><li>The catabolism of various molecules from food </li></ul>Amino  acids Sugars Glycerol Fatty acids Glycolysis Glucos...
Biosynthesis (Anabolic Pathways) <ul><li>The body </li></ul><ul><ul><li>Uses small molecules to build other substances </l...
Regulation of Cellular Respiration via Feedback Mechanisms <ul><li>Cellular respiration </li></ul><ul><ul><li>Is controlle...
<ul><li>The control of cellular respiration </li></ul>Glucose Glycolysis Fructose-6-phosphate Phosphofructokinase Fructose...
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Chapter 9 Cell Respiration
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Hyde Park Academy

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  1. 1. Chapter 9 Cellular Respiration: Harvesting Chemical Energy
  2. 2. <ul><li>Overview: Life Is Work </li></ul><ul><li>Living cells </li></ul><ul><ul><li>Require transfusions of energy from outside sources to perform their many tasks </li></ul></ul>
  3. 3. <ul><li>The giant panda </li></ul><ul><ul><li>Obtains energy for its cells by eating plants </li></ul></ul>Figure 9.1
  4. 4. <ul><li>Energy </li></ul><ul><ul><li>Flows into an ecosystem as sunlight and leaves as heat </li></ul></ul>Light energy ECOSYSTEM CO 2 + H 2 O Photosynthesis in chloroplasts Cellular respiration in mitochondria Organic molecules + O 2 ATP powers most cellular work Heat energy Figure 9.2
  5. 5. <ul><li>Concept 9.1: Catabolic pathways yield energy by oxidizing organic fuels </li></ul><ul><li>These fuels can consists of high energy molecules such as ____________ and ________ </li></ul><ul><li>These molecules are rich in Carbon and Hydrogen. The actual energy is found in the bonds of the molecule. Hydrogen atoms provide an excellent source of energy by means of their _________. </li></ul>
  6. 6. Catabolic Pathways and Production of ATP <ul><li>The breakdown of organic molecules is exergonic </li></ul><ul><li>All exergonic reactions release ________. </li></ul><ul><li>All endergonic reactions require _________. </li></ul><ul><li>Free energy can be defined as the energy available for a system to perform work when temperature and pressure are constant throughout the system. This environment is present within certain cellular components of the body. </li></ul><ul><li>The quantitative value of free energy (G) in exergonic reactions is always negative because there is a net release of free energy. (-G) In endergonic reactions, since energy is required the free energy would be ______, due to a net gain in free energy. </li></ul><ul><li>The ________ the decrease in free energy, the greater amount of work the reaction can perform. </li></ul>
  7. 7. <ul><li>Cellular respiration </li></ul><ul><ul><li>Is the most prevalent and efficient catabolic pathway </li></ul></ul><ul><ul><li>Consumes oxygen and organic molecules such as glucose </li></ul></ul><ul><ul><li>Yields ATP </li></ul></ul><ul><ul><li>ATP is the energy currency of the cell. </li></ul></ul>
  8. 8. <ul><li>To keep working </li></ul><ul><ul><li>Cells must regenerate _______ </li></ul></ul>
  9. 9. Redox Reactions: Oxidation and Reduction <ul><li>Catabolic pathways yield energy </li></ul><ul><ul><li>Due to the transfer of electrons </li></ul></ul>
  10. 10. The Principle of Redox <ul><li>Redox reactions </li></ul><ul><ul><li>Transfer electrons from one reactant to another by oxidation and reduction </li></ul></ul>
  11. 11. <ul><li>In oxidation </li></ul><ul><ul><li>A substance loses electrons, or is oxidized </li></ul></ul><ul><li>In reduction </li></ul><ul><ul><li>A substance gains electrons, or is reduced </li></ul></ul><ul><ul><li>The reducing agent is the substance that __________ electrons. </li></ul></ul><ul><ul><li>The oxidizing agent is the substance that ________ the electrons. </li></ul></ul>
  12. 12. <ul><li>Examples of redox reactions </li></ul>Na + Cl Na + + Cl – becomes oxidized (loses electron) becomes reduced (gains electron)
  13. 13. <ul><li>Some redox reactions </li></ul><ul><ul><li>Do not completely exchange electrons </li></ul></ul><ul><ul><li>Change the degree of electron sharing in covalent bonds </li></ul></ul><ul><ul><li>The greater the atoms electronegativity, the stronger its pull on electrons. </li></ul></ul><ul><ul><li>_______ has the greatest electronegativity among all the elements. </li></ul></ul>CH 4 H H H H C O O O O O C H H Methane (reducing agent) Oxygen (oxidizing agent) Carbon dioxide Water + 2O 2 CO 2 + Energy + 2 H 2 O becomes oxidized becomes reduced Reactants Products Figure 9.3
  14. 14. Oxidation of Organic Fuel Molecules During Cellular Respiration <ul><li>During cellular respiration </li></ul><ul><ul><li>Glucose is oxidized and oxygen is reduced </li></ul></ul><ul><ul><li>The transfer of electrons are in the form of ________ atoms. </li></ul></ul>C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + Energy becomes oxidized becomes reduced
  15. 15. Stepwise Energy Harvest via NAD + and the Electron Transport Chain <ul><li>Cellular respiration </li></ul><ul><ul><li>Oxidizes glucose in a series of steps </li></ul></ul>
  16. 16. <ul><li>Electrons from organic compounds </li></ul><ul><ul><li>Are usually first transferred to NAD + , a coenzyme </li></ul></ul>NAD + H O O O O – O O O – O O O P P CH 2 CH 2 HO OH H H HO OH HO H H N + C NH 2 H N H NH 2 N N Nicotinamide (oxidized form) NH 2 + 2[H] (from food) Dehydrogenase Reduction of NAD + Oxidation of NADH 2 e – + 2 H + 2 e – + H + NADH O H H N C + Nicotinamide (reduced form) N Figure 9.4
  17. 17. <ul><li>NADH, the reduced form of NAD + </li></ul><ul><ul><li>Passes the electrons to the electron transport chain </li></ul></ul>
  18. 18. <ul><li>If electron transfer is not stepwise </li></ul><ul><ul><li>A large release of energy occurs </li></ul></ul><ul><ul><li>As in the reaction of hydrogen and oxygen to form water </li></ul></ul>(a) Uncontrolled reaction Free energy, G H 2 O Explosive release of heat and light energy Figure 9.5 A H 2 + 1 / 2 O 2
  19. 19. <ul><li>The electron transport chain </li></ul><ul><ul><li>Passes electrons in a series of steps instead of in one explosive reaction </li></ul></ul><ul><ul><li>Uses the energy from the electron transfer to form ATP </li></ul></ul>
  20. 20. 2 H 1 / 2 O 2 (from food via NADH) 2 H + + 2 e – 2 H + 2 e – H 2 O 1 / 2 O 2 Controlled release of energy for synthesis of ATP ATP ATP ATP Electron transport chain Free energy, G (b) Cellular respiration + Figure 9.5 B
  21. 21. The Stages of Cellular Respiration: A Preview <ul><li>Respiration is a cumulative function of three metabolic stages </li></ul><ul><ul><li>Glycolysis </li></ul></ul><ul><ul><li>The citric acid cycle </li></ul></ul><ul><ul><li>Oxidative phosphorylation </li></ul></ul>
  22. 22. <ul><li>Anaerobic : Without Oxygen </li></ul><ul><li>Aerobic : With Oxygen </li></ul><ul><li>Glycolysis </li></ul><ul><ul><li>Breaks down glucose into two molecules of pyruvate </li></ul></ul><ul><li>The citric acid cycle </li></ul><ul><ul><li>Completes the breakdown of glucose </li></ul></ul><ul><ul><li>It does this when oxygen is not available </li></ul></ul>
  23. 23. <ul><li>Oxidative Phosphorylation </li></ul><ul><ul><li>Is driven by the electron transport chain (ETC). </li></ul></ul><ul><ul><li>Generates ATP by transferring an inorganic phosphate to ADP. </li></ul></ul><ul><ul><li>Generates ATP by means of a hydrogen ion gradient. </li></ul></ul>
  24. 24. <ul><li>An overview of cellular respiration </li></ul>Figure 9.6 Electrons carried via NADH Glycolsis Glucose Pyruvate ATP Substrate-level phosphorylation Electrons carried via NADH and FADH 2 Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis ATP ATP Substrate-level phosphorylation Oxidative phosphorylation Mitochondrion Cytosol
  25. 25. <ul><li>Both glycolysis and the citric acid cycle </li></ul><ul><ul><li>Can generate ATP by _________ level phosphorylation. An inorganic phosphate is added to a substrate. The reaction is enzymatically catalyzed to produce ATP and a product. </li></ul></ul>Figure 9.7 Enzyme Enzyme ATP ADP Product Substrate P +
  26. 26. <ul><li>Concept 9.2: Glycolysis harvests energy by oxidizing glucose to pyruvate </li></ul><ul><li>Glycolysis </li></ul><ul><ul><li>Means “splitting of sugar” </li></ul></ul><ul><ul><li>Breaks down glucose into pyruvate </li></ul></ul><ul><ul><li>Occurs in the cytoplasm of the cell </li></ul></ul>
  27. 27. <ul><li>Glycolysis consists of two major phases </li></ul><ul><ul><li>Energy investment phase </li></ul></ul><ul><ul><li>Energy payoff phase </li></ul></ul>Glycolysis Citric acid cycle Oxidative phosphorylation ATP ATP ATP 2 ATP 4 ATP used formed Glucose 2 ATP + 2 P 4 ADP + 4 P 2 NAD + + 4 e - + 4 H + 2 NADH + 2 H + 2 Pyruvate + 2 H 2 O Energy investment phase Energy payoff phase Glucose 2 Pyruvate + 2 H 2 O 4 ATP formed – 2 ATP used 2 ATP 2 NAD + + 4 e – + 4 H + 2 NADH + 2 H + Figure 9.8
  28. 28. Dihydroxyacetone phosphate Glyceraldehyde- 3-phosphate H H H H H OH OH HO HO CH 2 OH H H H H O H OH HO OH P CH 2 O P H O H HO HO H HO CH 2 OH P O CH 2 O CH 2 O P HO H HO H OH O P CH 2 C O CH 2 OH H C CHOH CH 2 O O P ATP ADP Hexokinase Glucose Glucose-6-phosphate Fructose-6-phosphate ATP ADP Phosphoglucoisomerase Phosphofructokinase Fructose- 1, 6-bisphosphate Aldolase Isomerase Glycolysis 1 2 3 4 5 CH 2 OH Oxidative phosphorylation Citric acid cycle Figure 9.9 A
  29. 29. 2 NAD + NADH 2 + 2 H + Triose phosphate dehydrogenase 2 P i 2 P C CHOH O P O CH 2 O 2 O – 1, 3-Bisphosphoglycerate 2 ADP 2 ATP Phosphoglycerokinase CH 2 O P 2 C CHOH 3-Phosphoglycerate Phosphoglyceromutase O – C C CH 2 OH H O P 2-Phosphoglycerate 2 H 2 O 2 O – Enolase C C O P O CH 2 Phosphoenolpyruvate 2 ADP 2 ATP Pyruvate kinase O – C C O O CH 3 2 6 8 7 9 10 Pyruvate O Figure 9.8 B
  30. 30. <ul><li>Concept 9.3: The citric acid cycle completes the energy-yielding oxidation of organic molecules </li></ul><ul><li>The citric acid cycle </li></ul><ul><ul><li>Takes place in the ________ of the mitochondrion </li></ul></ul>
  31. 31. <ul><li>Before the citric acid cycle can begin </li></ul><ul><ul><li>Pyruvate must first be converted to acetyl CoA, which links the cycle to glycolysis </li></ul></ul>CYTOSOL MITOCHONDRION NADH + H + NAD + 2 3 1 CO 2 Coenzyme A Pyruvate Acetyle CoA S CoA C CH 3 O Transport protein O – O O C C CH 3 Figure 9.10
  32. 32. <ul><li>An overview of the citric acid cycle </li></ul>ATP 2 CO 2 3 NAD + 3 NADH + 3 H + ADP + P i FAD FADH 2 Citric acid cycle CoA CoA Acetyle CoA NADH + 3 H + CoA CO 2 Pyruvate (from glycolysis, 2 molecules per glucose) ATP ATP ATP Glycolysis Citric acid cycle Oxidative phosphorylation Figure 9.11
  33. 33. <ul><li>A closer look at the citric acid cycle </li></ul>
  34. 34. Figure 9.12 Acetyl CoA NADH Oxaloacetate Citrate Malate Fumarate Succinate Succinyl CoA  -Ketoglutarate Isocitrate Citric acid cycle S CoA CoA SH NADH NADH FADH 2 FAD GTP GDP NAD + ADP P i NAD + CO 2 CO 2 CoA SH CoA SH CoA S H 2 O + H + + H + H 2 O C CH 3 O O C COO – CH 2 COO – COO – CH 2 HO C COO – CH 2 COO – COO – COO – CH 2 HC COO – HO CH COO – CH CH 2 COO – HO COO – CH HC COO – COO – CH 2 CH 2 COO – COO – CH 2 CH 2 C O COO – CH 2 CH 2 C O COO – 1 2 3 4 5 6 7 8 Glycolysis Oxidative phosphorylation NAD + + H + ATP Citric acid cycle Figure 9.12
  35. 35. <ul><li>Concept 9.4: During oxidative phosphorylation, ____________ couples electron transport to ATP synthesis </li></ul><ul><li>NADH and FADH 2 </li></ul><ul><ul><li>Donate electrons to the electron transport chain, which powers ATP synthesis via oxidative phosphorylation </li></ul></ul>
  36. 36. The Pathway of Electron Transport <ul><li>In the electron transport chain </li></ul><ul><ul><li>Electrons from NADH and FADH 2 lose energy in several steps </li></ul></ul>
  37. 37. <ul><li>At the end of the chain </li></ul><ul><ul><li>Electrons are passed to oxygen, forming water </li></ul></ul><ul><ul><li>Oxygen has the greatest affinity </li></ul></ul><ul><ul><li>for electrons (electronegative) </li></ul></ul>H 2 O O 2 NADH FADH2 FMN Fe•S Fe•S Fe•S O FAD Cyt b Cyt c 1 Cyt c Cyt a Cyt a 3 2 H + + 1  2 I II III IV Multiprotein complexes 0 10 20 30 40 50 Free energy ( G ) relative to O 2 (kcl/mol) Figure 9.13
  38. 38. Chemiosmosis: The Energy-Coupling Mechanism <ul><li>ATP synthase </li></ul><ul><ul><li>Is the enzyme that actually makes ATP </li></ul></ul>INTERMEMBRANE SPACE H + H + H + H + H + H + H + H + P i + ADP ATP A rotor within the membrane spins clockwise when H + flows past it down the H + gradient. A stator anchored in the membrane holds the knob stationary. A rod (for “stalk”) extending into the knob also spins, activating catalytic sites in the knob. Three catalytic sites in the stationary knob join inorganic Phosphate to ADP to make ATP. MITOCHONDRIAL MATRIX Figure 9.14
  39. 39. <ul><li>At certain steps along the electron transport chain (ETC) </li></ul><ul><ul><li>Electron transfer causes protein complexes to pump H + from the mitochondrial matrix to the intermembrane space. </li></ul></ul><ul><ul><li>These Hydrogen ions are from the electron carriers _______ and ________ after they become _______. </li></ul></ul>
  40. 40. <ul><li>The resulting H + gradient </li></ul><ul><ul><li>Stores energy </li></ul></ul><ul><ul><li>Drives chemiosmosis in ATP synthase </li></ul></ul><ul><ul><li>Is referred to as a ________-motive force </li></ul></ul>
  41. 41. <ul><li>Chemiosmosis </li></ul><ul><ul><li>Is an energy-coupling mechanism that uses ________ in the form of a H + gradient across a membrane to drive cellular work </li></ul></ul>
  42. 42. <ul><li>Chemiosmosis and the electron transport chain </li></ul>Oxidative phosphorylation. electron transport and chemiosmosis Glycolysis ATP ATP ATP Inner Mitochondrial membrane H + H + H + H + H + ATP P i Protein complex of electron carners Cyt c I II III IV (Carrying electrons from, food) NADH + FADH 2 NAD + FAD + 2 H + + 1 / 2 O 2 H 2 O ADP + Electron transport chain Electron transport and pumping of protons (H + ), which create an H + gradient across the membrane Chemiosmosis ATP synthesis powered by the flow Of H + back across the membrane ATP synthase Q Oxidative phosphorylation Intermembrane space Inner mitochondrial membrane Mitochondrial matrix Figure 9.15
  43. 43. An Accounting of ATP Production by Cellular Respiration <ul><li>During respiration, most energy flows in this sequence </li></ul><ul><ul><li>Glucose to NADH to electron transport chain to proton-motive force to ATP </li></ul></ul>
  44. 44. <ul><li>There are three main processes in this metabolic enterprise </li></ul>Electron shuttles span membrane CYTOSOL 2 NADH 2 FADH 2 2 NADH 6 NADH 2 FADH 2 2 NADH Glycolysis Glucose 2 Pyruvate 2 Acetyl CoA Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis MITOCHONDRION by substrate-level phosphorylation by substrate-level phosphorylation by oxidative phosphorylation, depending on which shuttle transports electrons from NADH in cytosol Maximum per glucose: About 36 or 38 ATP + 2 ATP + 2 ATP + about 32 or 34 ATP or Figure 9.16
  45. 45. <ul><li>About 40% of the energy in a glucose molecule </li></ul><ul><ul><li>Is transferred to ATP during cellular respiration, making approximately 38 ATP </li></ul></ul>
  46. 46. <ul><li>Concept 9.5: Fermentation enables some cells to produce ATP without the use of oxygen </li></ul><ul><li>Cellular respiration </li></ul><ul><ul><li>Relies on oxygen to produce ATP </li></ul></ul><ul><li>In the absence of oxygen </li></ul><ul><ul><li>Cells can still produce ATP through fermentation </li></ul></ul>
  47. 47. <ul><li>Glycolysis </li></ul><ul><ul><li>Can produce ATP with or without oxygen, in aerobic or anaerobic conditions </li></ul></ul><ul><ul><li>Couples with fermentation to produce ATP </li></ul></ul>
  48. 48. Types of Fermentation <ul><li>Fermentation consists of </li></ul><ul><ul><li>Glycolysis plus reactions that regenerate NAD + , which can be reused by glyocolysis </li></ul></ul>
  49. 49. <ul><li>In alcohol fermentation </li></ul><ul><ul><li>Pyruvate is converted to ethanol in two steps, one of which releases CO 2 </li></ul></ul>
  50. 50. <ul><li>During lactic acid fermentation </li></ul><ul><ul><li>Pyruvate is reduced directly to NADH to form lactate as a waste product </li></ul></ul>
  51. 51. 2 ADP + 2 P 1 2 ATP Glycolysis Glucose 2 NAD + 2 NADH 2 Pyruvate 2 Acetaldehyde 2 Ethanol (a) Alcohol fermentation 2 ADP + 2 P 1 2 ATP Glycolysis Glucose 2 NAD + 2 NADH 2 Lactate (b) Lactic acid fermentation H H OH CH 3 C O – O C C O CH 3 H C O CH 3 O – C O C O CH 3 O C O C OH H CH 3 CO 2 2 Figure 9.17
  52. 52. Fermentation and Cellular Respiration Compared <ul><li>Both fermentation and cellular respiration </li></ul><ul><ul><li>Use glycolysis to oxidize glucose and other organic fuels to pyruvate </li></ul></ul>
  53. 53. <ul><li>Fermentation and cellular respiration </li></ul><ul><ul><li>Differ in their final electron acceptor </li></ul></ul><ul><li>Cellular respiration </li></ul><ul><ul><li>Produces more ATP </li></ul></ul>
  54. 54. <ul><li>Pyruvate is a key juncture in catabolism </li></ul>Glucose CYTOSOL Pyruvate No O 2 present Fermentation O 2 present Cellular respiration Ethanol or lactate Acetyl CoA MITOCHONDRION Citric acid cycle Figure 9.18
  55. 55. The Evolutionary Significance of Glycolysis <ul><li>Glycolysis </li></ul><ul><ul><li>Occurs in nearly all organisms </li></ul></ul><ul><ul><li>Probably evolved in ancient prokaryotes before there was oxygen in the atmosphere </li></ul></ul>
  56. 56. <ul><li>Concept 9.6: Glycolysis and the citric acid cycle connect to many other metabolic pathways </li></ul>
  57. 57. The Versatility of Catabolism <ul><li>Catabolic pathways </li></ul><ul><ul><li>Funnel electrons from many kinds of organic molecules into cellular respiration </li></ul></ul>
  58. 58. <ul><li>The catabolism of various molecules from food </li></ul>Amino acids Sugars Glycerol Fatty acids Glycolysis Glucose Glyceraldehyde-3- P Pyruvate Acetyl CoA NH 3 Citric acid cycle Oxidative phosphorylation Fats Proteins Carbohydrates Figure 9.19
  59. 59. Biosynthesis (Anabolic Pathways) <ul><li>The body </li></ul><ul><ul><li>Uses small molecules to build other substances </li></ul></ul><ul><li>These small molecules </li></ul><ul><ul><li>May come directly from food or through glycolysis or the citric acid cycle </li></ul></ul>
  60. 60. Regulation of Cellular Respiration via Feedback Mechanisms <ul><li>Cellular respiration </li></ul><ul><ul><li>Is controlled by allosteric enzymes at key points in glycolysis and the citric acid cycle </li></ul></ul>
  61. 61. <ul><li>The control of cellular respiration </li></ul>Glucose Glycolysis Fructose-6-phosphate Phosphofructokinase Fructose-1,6-bisphosphate Inhibits Inhibits Pyruvate ATP Acetyl CoA Citric acid cycle Citrate Oxidative phosphorylation Stimulates AMP + – – Figure 9.20
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