1. Cellular Respiration and Fermentation chapter 9

2. Catabolic Pathways and Production of ATP Breakdown – exergonic process Breakdown – exergonic process Cellular Respiration  produces energy Cellular Respiration  produces energy Two fundamental processes Two fundamental processes  Substrate-level phosphorylation  Oxidative phosphorylation -- ~90% 2

3. Substrate-level phosphorylation – Direct transfer of a phosphate to ADP to make ATP Substrate-level phosphorylation – Direct transfer of a phosphate to ADP to make ATP 3 Enzyme ADP P Substrate Product Enzyme ATP + Synthesis of ATP – 2 Methods

4. 4 Oxidative phosphorylation – production using energy derived from transfer of electrons & occuring via chemiosmosis 4

5. 5 Redox Reactions  Oxidation-reduction reactions -- redox reactions  Oxidation – loss of electrons  Reduction – gain of electrons  Not reversible! Xe - + Y X + Ye - becomes oxidized (loses electron) becomes reduced (gains electron)

6. 6 Reducing Agent -- electron donor – gets oxidized! Reducing Agent -- electron donor – gets oxidized! Oxidizing Agent -- electron receptor – gets reduced! Oxidizing Agent -- electron receptor – gets reduced! Leo Ger Loss of Electrons – Oxidation Gain of Electrons -- Reduction Oxidation Is Loss; Reduction Is Gain

7. Catabolic Pathways Two fundamental “kinds” Two fundamental “kinds”  Using organic molecules  Using inorganic molecules (prokaryotes only) Breakdown of organic molecules Breakdown of organic molecules  Aerobic – requires oxygen  Anaerobic (fermentation) – absence of oxygen Copyright © 2008 Pearson Education, Inc., publishing as Pearson Benjamin Cummings 7

8. Cellular Respiration Both aerobic and anaerobic pathways Both aerobic and anaerobic pathways Any organic fuel Any organic fuel  carbohydrates, fats, and proteins Generally start with glucose Generally start with glucose C 6 H 12 O 6 + 6 O 2  6 CO 2 + 6 H 2 O + Energy (ATP + heat) C 6 H 12 O 6 + 6 O 2  6 CO 2 + 6 H 2 O + Energy (ATP + heat) 8

9. 9 Organic Fuel is Oxidized ReDox process ReDox process  During cellular respiration, the fuel (such as glucose) is oxidized and oxygen is reduced: C 6 H 12 O 6 + 6O 2 6CO 2 + 6H 2 O + Energy becomes oxidized becomes reduced

10. 10 Stepwise Energy Harvest Glucose -- broken down in a series of steps Glucose -- broken down in a series of steps Electron transport chain -- series of steps instead of one explosive reaction Electron transport chain -- series of steps instead of one explosive reaction

11. LE 9-5 2 H + + 2 e – 2 H (from food via NADH) Controlled release of energy for synthesis of ATP 2 H + 2 e – H2OH2O + 1 / 2 O 2 H2H2 + H2OH2O Explosive release of heat and light energy Cellular respiration Uncontrolled reaction Free energy, G Electron transport chain

12. 12 RESPIRATION C 6 H 12 O 6 + O 2 CO 2 + H 2 O + ENERGY ATP 686 kcal/mole (180 grams)

13. 13 Glycolysis: glucose to pyruvate Glycolysis -- glucose into two molecules of pyruvate Glycolysis -- glucose into two molecules of pyruvate Glycolysis -- occurs in the cytoplasm Glycolysis -- occurs in the cytoplasm  Energy investment phase  Energy payoff phase  Independent reaction

14. LE 9-8 Energy investment phase Glucose 2 ATP used 2 ADP + 2 P 4 ADP + 4 P 4 ATP formed 2 NAD + + 4 e – + 4 H + Energy payoff phase + 2 H + 2 NADH 2 Pyruvate + 2 H 2 O 2 ATP 2 NADH + 2 H + Glucose 4 ATP formed – 2 ATP used 2 NAD+ + 4 e – + 4 H + Net Glycolysis Citric acid cycle Oxidative phosphorylation ATP

15. 15 Glycolysis 10 steps – specific enzyme 10 steps – specific enzyme Energy Investment Energy Investment  Glucose to 2 PGAL  uses ATP Energy Payoff Energy Payoff  PGAL to Pyruvic Acid  Produces ATP  PGAL/ G3P – phosphoglyceraldehyde or glyceraldehyde-3-phosphate

16. 16 Fig. 8-3, p. 175 GLYCOLYSIS Energy investment phase and splitting of glucose Two ATPs invested per glucose Glucose 3 steps 2 ATP 2 ADP Fructose-1,6-bisphosphate P P PP Glyceraldehyde phosphate (G3P) Glyceraldehyde phosphate (G3P) PGAL

17. 17 Fig. 8-3, p. 175 Energy capture phase Four ATPs and two NADH produced per glucose PP (G3P) NAD + NADH 2 ADP 2 ATP Pyruvate 5 steps NADH 2 ADP 2 ATP Net yield per glucose: Two ATPs and two NADH Pyruvate NADH

18. Glycolysis Is Glycolysis really a part of Aerobic Cellular Respiration? Is Glycolysis really a part of Aerobic Cellular Respiration? Occurs in both Aerobic and Anaerobic Respiration! Occurs in both Aerobic and Anaerobic Respiration! 18

19. Steps of Respiration 3? 4? 5? 3? 4? 5? Glycolysis Glycolysis Formation of Acetyl Co-Enzyme A Formation of Acetyl Co-Enzyme A Krebs Cycle Krebs Cycle Electron Transport Chain Electron Transport Chain Chemiosmosis Chemiosmosis 19

20. 20 Pyruvate Glucose CYTOSOL No O 2 present Fermentation or Anaerobic respiration Ethanol or lactate Acetyl CoA MITOCHONDRION O 2 present -- Aerobic cellular respiration Citric acid cycle Glycolysis …. What next? Glycolysis

21. 21 Formation of Acetyl Co-A CYTOSOL Pyruvate NAD + MITOCHONDRION Transport protein NADH + H + Coenzyme ACO 2 Acetyl Co A

22. 22 Formation of Acetyl CoA 1 pyruvate molecule 1 pyruvate molecule  loses 1 molecule of carbon dioxide Acetyl group + coenzyme A Acetyl group + coenzyme A  produce acetyl CoA 1 NADH produced per pyruvate 1 NADH produced per pyruvate NAD + Coenzyme A Acetyl coenzyme A Pyruvate Carbon dioxide CO 2 NADH

23. 23 Different terms Different terms  The citric acid cycle  The Krebs cycle  The Tricarboxylic Acid Cycle Oxidizes acetyl co-A (fuel derived from pyruvate) Oxidizes acetyl co-A (fuel derived from pyruvate) Produced PER Acetyl Co-A Produced PER Acetyl Co-A  1 ATP  3 NADH  1 FADH 2  2 CO 2 Citric Acid Cycle

24. LE 9-11 Pyruvate (from glycolysis, 2 molecules per glucose) ATP Glycolysis Oxidation phosphorylation Citric acid cycle NAD + NADH + H + CO 2 CoA Acetyl CoA CoA Citric acid cycle CO 2 2 3 NAD + + 3 H + NADH3 ATP ADP + P i FADH 2 FAD

25. 25 Citric Acid Cycle 1 acetyl CoA enters cycle 1 acetyl CoA enters cycle  combines with 4-C oxaloacetate  forms 6-C citrate Citrate decomposed back to oxaloacetate Citrate decomposed back to oxaloacetate 2 C enter as acetyl CoA -- 2 leave as CO 2 2 C enter as acetyl CoA -- 2 leave as CO 2 1 acetyl CoA 1 acetyl CoA  transfers H atoms to 3 NAD +, 1 FAD  1 ATP produced NADH and FADH 2 -- electrons to electron transport chain NADH and FADH 2 -- electrons to electron transport chain

26. 26 Fig. 8-6, p. 179 Oxaloacetate NADH NAD + H2OH2O FADH 2 FAD GTP GDP ADP ATP C I T R I C A C I D C Y C L E 4-carbon compound Acetyl coenzyme A Coenzyme A Citrate NAD + NADH CO 2 NADH 5-carbon compound

27. 27 Electron Transport Chain  NADH and FADH 2  account for most of the energy extracted from food  Donate electrons to the electron transport chain Probably the most important step Probably the most important step

28. 28 The electron transport chain generates no ATP The electron transport chain generates no ATP  Moves electrons around Function -- break the large free-energy drop from food to O 2 releasing energy in manageable amounts Function -- break the large free-energy drop from food to O 2 releasing energy in manageable amounts  Alternating oxidized and reduced states  Maintains pH gradient Electrons drop in free energy until passed to O 2 forming water Electrons drop in free energy until passed to O 2 forming water Electron Transport Chain

29. 29 Electron Transport Chain Chemiosmosis 4 2 4

30. LE 9-13 ATP Glycolysis Oxidative phosphorylation: electron transport and chemiosmosis Citric acid cycle NADH 50 FADH 2 40 FMN FeS I FAD FeS II III Q FeS Cyt b 30 20 Cyt c Cyt c 1 Cyt a Cyt a 3 IV 10 0 Multiprotein complexes Free energy (G) relative to O2 (kcal/mol) H2OH2O O2O2 2 H + + 1 / 2

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32. 32 Chemiosmosis ✥ Paul Mitchell theorized in 1961 ✥ Nobel Prize in Chemistry in 1978 ✥ Energy stored in pH gradient

33. 33 Chemiosmosis: The Energy- Coupling Mechanism Electron transfer -- proteins pump H + from mitochondrial matrix to intermembrane space Electron transfer -- proteins pump H + from mitochondrial matrix to intermembrane space  Chemiosmosis -- use of energy in a H + gradient to drive cellular work H + through channels in ATP synthase H + through channels in ATP synthase ATP synthase uses the exergonic flow to drive phosphorylation of ATP ATP synthase uses the exergonic flow to drive phosphorylation of ATP

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36. 36 CO 2 H2OH2O

37. 37 Electron transport chain inhibitors  Lack of organic fuel  Cyanide & Carbon monoxide  Blocks IV  Rotenone & Amytal  Blocks I Oligomycin Oligomycin  Blocks ATP synthase Antimycin Antimycin  Blocks III

38. 38 CYANIDE RESISTANT RESPIRATION Aerobic respiration is inhibited when the terminal electron carrier combines with cyanide, azide or certain other negatively charged ions This poisons the enzyme and stops electron transport

39. 39 CYANIDE RESISTANT RESPIRATION  Some plants, fungi and bacteria  This pathway produces heat rather than ATPs but is aerobic (i.e., oxygen is the terminal electron acceptor)  The heat produced by some plants has important ecological functions.

40. 40 This seems to be important when electron transport is saturated

41. 41 When it flowers -- heats to as high as 46 C (115 F). The heat protects the flowers from freezing at night and disperses compound that attract pollinators Light energy —> Heat Energy is captured from light by Philodendron leaves and used for life processes and growth

42. Skunk Cabbage Air temp – 5-50 ˚F Air temp – 5-50 ˚F  -15-10 ˚C Flower temp – 60-72 ˚F Flower temp – 60-72 ˚F  15-22 ˚C Some flowers generate 0.4 J heat/second/gram whereas hummingbirds generate 0.24 J heat/second/gram Some flowers generate 0.4 J heat/second/gram whereas hummingbirds generate 0.24 J heat/second/gram 42

43. 43 An Accounting of ATP Production by Cellular Respiration During cellular respiration -- energy flows in this sequence: During cellular respiration -- energy flows in this sequence: glucose  NADH  electron transport chain  pH gradient  ATP About 40% of the energy is transferred to ATP -- making about 38 ATP About 40% of the energy is transferred to ATP -- making about 38 ATP

44. LE 9-16 CYTOSOL Electron shuttles span membrane 2 NADH or 2 FADH 2 MITOCHONDRION Oxidative phosphorylation: electron transport and chemiosmosis 2 FADH 2 2 NADH6 NADH Citric acid cycle 2 Acetyl CoA 2 NADH Glycolysis Glucose 2 Pyruvate + 2 ATP by substrate-level phosphorylation + 2 ATP by substrate-level phosphorylation + about 32 or 34 ATP by oxidation phosphorylation, depending on which shuttle transports electrons form NADH in cytosol About 36 or 38 ATP Maximum per glucose:

45. 45 Facultative anaerobes -- they can survive using either fermentation or cellular respiration Facultative anaerobes -- they can survive using either fermentation or cellular respiration Pyruvate is a fork in the metabolic road that leads to two alternative catabolic routes Pyruvate is a fork in the metabolic road that leads to two alternative catabolic routes Fermentation

46. 46 Pyruvate Glucose CYTOSOL No O 2 present Fermentation or Anaerobic respiration Ethanol or lactate Acetyl CoA MITOCHONDRION O 2 present -- Aerobic cellular respiration Citric acid cycle Glycolysis

47. 47 Fermentation vs Respiration Glycolysis -- oxidizes glucose to pyruvate Glycolysis -- oxidizes glucose to pyruvate Different final electron acceptors Different final electron acceptors  Fermentation -- an organic molecule (such as pyruvate)  Respiration -- O 2 Aerobic respiration produces much more ATP Aerobic respiration produces much more ATP

48. 48 Types of Fermentation Fermentation -- glycolysis plus reactions that regenerate NAD +, which can be reused by glycolysis Fermentation -- glycolysis plus reactions that regenerate NAD +, which can be reused by glycolysis Two types Two types  alcohol fermentation  lactic acid fermentation

49. 49 pyruvate is converted to ethanol in two steps, with the first releasing CO 2 pyruvate is converted to ethanol in two steps, with the first releasing CO 2 yeast -- brewing, winemaking, and baking yeast -- brewing, winemaking, and baking Alcohol Fermentation

50. LE 9-17a CO 2 + 2 H + 2 NADH2 NAD + 2 Acetaldehyde 2 ATP 2 ADP + 2 P i 2 Pyruvate 2 2 Ethanol Alcohol fermentation Glucose Glycolysis

51. 51 pyruvate is reduced to NADH, forming lactate as an end product, with no release of CO 2 pyruvate is reduced to NADH, forming lactate as an end product, with no release of CO 2 fungi and bacteria -- cheese and yogurt fungi and bacteria -- cheese and yogurt muscle cells -- lactic acid fermentation muscle cells -- lactic acid fermentation Lactic Acid Fermentation

52. LE 9-17b + 2 H + 2 NADH2 NAD + 2 ATP 2 ADP + 2 P i 2 Pyruvate 2 Lactate Lactic acid fermentation Glucose Glycolysis

53. 53 Glycolysis and metabolic pathways Gycolysis and the citric acid cycle are major intersections to various catabolic and anabolic pathways Gycolysis and the citric acid cycle are major intersections to various catabolic and anabolic pathways

54. LE 9-19 Citric acid cycle Oxidative phosphorylation Proteins NH 3 Amino acids Sugars Carbohydrates Glycolysis Glucose Glyceraldehyde-3- P Pyruvate Acetyl CoA Fatty acids Glycerol Fats

55. 55 The Versatility of Catabolism funnel electrons into cellular respiration funnel electrons into cellular respiration wide range of carbohydrates wide range of carbohydrates amino groups can feed glycolysis or the citric acid cycle amino groups can feed glycolysis or the citric acid cycle fats -- glycerol (used in glycolysis) and fatty acids (used in generating acetyl CoA) fats -- glycerol (used in glycolysis) and fatty acids (used in generating acetyl CoA)  a gram of fat > 2X ATP as an oxidized gram of carbohydrate

56. 56 FIGURE 6.1

57. 57 Biosynthesis (Anabolic Pathways) The body uses small molecules to build other substances The body uses small molecules to build other substances These small molecules may come directly from food, from glycolysis, or from the citric acid cycle These small molecules may come directly from food, from glycolysis, or from the citric acid cycle

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59. 59 Regulation of Cellular Respiration: Feedback Mechanisms most common mechanism for control most common mechanism for control If ATP concentration drop -- respiration speeds up If ATP concentration drop -- respiration speeds up Enzyme control at strategic points in the catabolic pathway Enzyme control at strategic points in the catabolic pathway

60. LE 9-20 Citric acid cycle Oxidative phosphorylation Glycolysis Glucose Pyruvate Acetyl CoA Fructose-6-phosphate Phosphofructokinase Fructose-1,6-bisphosphate – Inhibits ATP Citrate Inhibits Stimulates AMP + –

61. 61 PHOTORESPIRATION  Some plants increase their use of oxygen when CO 2 gets too low, a process known as photorespiration.  Photorespiration interferes with photosynthesis and causes decreased crop yield

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63. 63 Summary Reaction Complete oxidation of glucose Complete oxidation of glucose C 6 H 12 O 6 + 6 O 2 + 6 H 2 O → 6 CO 2 + 12 H 2 O + energy (36 to 38 ATP) 6 CO 2 + 12 H 2 O + energy (36 to 38 ATP) [40% of potential energy -> ATP 60% -> wasted (heat)]

64. 64 Summary Reaction Glycolysis Glycolysis C 6 H 12 O 6 + 2 ATP + 2 ADP + 2 P i + 2 NAD + → 2 pyruvate + 4 ATP + 2 NADH + H 2 O

65. 65 Summary Reaction Conversion of pyruvate to acetyl CoA Conversion of pyruvate to acetyl CoA 2 pyruvate + 2 coenzyme A + 2 NAD + → 2 acetyl CoA + 2 CO 2 + 2 NADH 2 acetyl CoA + 2 CO 2 + 2 NADH

66. 66 Summary Reaction Citric acid cycle Citric acid cycle 2 acetyl CoA + 6 NAD + + 2 FAD + 2 ADP + 2 P i + 2 H 2 O → 4 CO 2 + 6 NADH + + 2 P i + 2 H 2 O → 4 CO 2 + 6 NADH + 2 FADH 2 + 2 ATP + 2 CoA

67. 67 Summary Reactions Hydrogen atoms in Electron Transport Chain Hydrogen atoms in Electron Transport Chain NADH + 3 ADP + 3 P i + 12 O 2 → NAD + + 3 ATP + H 2 O FADH 2 + 2 ADP + 2 P i + 12 O 2 → FAD + 2 ATP + H 2 O

68. 68 Summary Reaction Lactate fermentation Lactate fermentation C 6 H 12 O 6 → 2 lactate + 2 ATP + NAD + Pyruvate → NAD + + lactate/lactic acid

69. 69 Summary Reaction Alcohol fermentation Alcohol fermentation C 6 H 12 O 6 → 2 CO 2 + 2 C 2 H 5 OH + 2 ATP + NAD + Pyruvate -> NAD + + ethanol + CO 2

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