1. Ch. 9 Cellular Respiration Living cells require energy from outside sources Heterotrophs and autotrophs Photosynthesis generates O 2 and organic molecules, which are used in cellular respiration Cells use chemical energy stored in organic molecules to regenerate ATP, which powers work © 2011 Pearson Education, Inc.

2. Figure 9.2 Light energy ECOSYSTEM Photosynthesis in chloroplasts Cellular respiration in mitochondria CO 2  H 2 O  O 2 Organic molecules ATP powers most cellular work ATP Heat energy

3. Cellular respiration is often used to refer to aerobic respiration C 6 H 12 O 6 + 6 O 2  6 CO 2 + 6 H 2 O + Energy (ATP + heat) © 2011 Pearson Education, Inc.

4. Redox Reactions During cellular respiration, the fuel (such as glucose) is oxidized, and O 2 is reduced © 2011 Pearson Education, Inc.

5. Figure 9.UN03 becomes oxidized becomes reduced

6. NAD + In cellular respiration, glucose and other organic molecules are broken down in a series of steps Electrons from organic compounds are usually first transferred to NAD +, a coenzyme As an electron acceptor, NAD + functions as an oxidizing agent during cellular respiration Each NADH (the reduced form of NAD + ) represents stored energy that will eventually synthesize ATP © 2011 Pearson Education, Inc.

7. Figure 9.4 Nicotinamide (oxidized form) NAD  (from food) Dehydrogenase Reduction of NAD  Oxidation of NADH Nicotinamide (reduced form) NADH

8. NADH passes the electrons to the electron transport chain O 2 pulls electrons down the chain in an energy- yielding tumble The energy yielded is used to regenerate ATP © 2011 Pearson Education, Inc.

9. Three stages of respiration Harvesting of energy from glucose has three stages –Glycolysis (breaks down glucose into two molecules of pyruvate) –The citric acid cycle and oxidation of pyruvate (completes the breakdown of glucose) –Oxidative phosphorylation – electron transport (accounts for most of the ATP synthesis) © 2011 Pearson Education, Inc.

10. Figure 9.UN05 Glycolysis (color-coded teal throughout the chapter) 1. Pyruvate oxidation and the citric acid cycle (color-coded salmon) 2. Oxidative phosphorylation: electron transport and chemiosmosis (color-coded violet) 3.

11. Figure 9.6-1 Electrons carried via NADH Glycolysis Glucose Pyruvate CYTOSOL MITOCHONDRION ATP Substrate-level phosphorylation

12. Figure 9.6-2 Electrons carried via NADH Electrons carried via NADH and FADH 2 Citric acid cycle Pyruvate oxidation Acetyl CoA Glycolysis Glucose Pyruvate CYTOSOL MITOCHONDRION ATP Substrate-level phosphorylation

13. Figure 9.6-3 Electrons carried via NADH Electrons carried via NADH and FADH 2 Citric acid cycle Pyruvate oxidation Acetyl CoA Glycolysis Glucose Pyruvate Oxidative phosphorylation: electron transport and chemiosmosis CYTOSOL MITOCHONDRION ATP Substrate-level phosphorylation Oxidative phosphorylation

14. The process that generates most of the ATP is called oxidative phosphorylation because it is powered by redox reactions A smaller amount of ATP is formed in glycolysis and the citric acid cycle by substrate-level phosphorylation For each molecule of glucose degraded to CO 2 and water by respiration, the cell makes up to 32 molecules of ATP © 2011 Pearson Education, Inc.

15. BioFlix: Cellular Respiration

16. Glycolysis Glycolysis (“splitting of sugar”) breaks down glucose into two molecules of pyruvate Glycolysis occurs in the cytoplasm and has two major phases –Energy investment phase –Energy payoff phase Glycolysis occurs whether or not O 2 is present © 2011 Pearson Education, Inc.

17. Figure 9.8 Energy Investment Phase Glucose 2 ADP  2 P 4 ADP  4 P Energy Payoff Phase 2 NAD +  4 e   4 H + 2 Pyruvate  2 H 2 O 2 ATP used 4 ATP formed 2 NADH  2 H + Net Glucose 2 Pyruvate  2 H 2 O 2 ATP 2 NADH  2 H + 2 NAD +  4 e   4 H + 4 ATP formed  2 ATP used

18. Figure 9.9a Glycolysis: Energy Investment Phase ATP Glucose Glucose 6-phosphate ADP Hexokinase 1 Fructose 6-phosphate Phosphogluco- isomerase 2

19. Figure 9.9b Glycolysis: Energy Investment Phase ATP Fructose 6-phosphate ADP 3 Fructose 1,6-bisphosphate Phospho- fructokinase 45 Aldolase Dihydroxyacetone phosphate Glyceraldehyde 3-phosphate To step 6 Isomerase

20. Figure 9.9c Glycolysis: Energy Payoff Phase 2 NADH 2 ATP 2 ADP 2 2 2 NAD  + 2 H  2 P i 3-Phospho- glycerate 1,3-Bisphospho- glycerate Triose phosphate dehydrogenase Phospho- glycerokinase 67

21. Figure 9.9d Glycolysis: Energy Payoff Phase 2 ATP 2 ADP 2 2 22 2 H 2 O Pyruvate Phosphoenol- pyruvate (PEP) 2-Phospho- glycerate 3-Phospho- glycerate 8 9 10 Phospho- glyceromutase Enolase Pyruvate kinase

22. In the presence of O 2, pyruvate enters the mitochondrion (in eukaryotic cells) where the oxidation of glucose is completed © 2011 Pearson Education, Inc.

23. Oxidation of Pyruvate to Acetyl CoA Before the citric acid cycle can begin, pyruvate must be converted to acetyl Coenzyme A (acetyl CoA), which links glycolysis to the citric acid cycle © 2011 Pearson Education, Inc.

24. Figure 9.10 Pyruvate Transport protein CYTOSOL MITOCHONDRION CO 2 Coenzyme A NAD  + H  NADH Acetyl CoA 123

25. The cycle oxidizes organic fuel derived from pyruvate, generating 1 ATP, 3 NADH, and 1 FADH 2 per turn © 2011 Pearson Education, Inc. The Citric Acid Cycle - Krebs

26. Figure 9.11 Pyruvate NAD  NADH + H  Acetyl CoA CO 2 CoA 2 CO 2 ADP + P i FADH 2 FAD ATP 3 NADH 3 NAD  Citric acid cycle + 3 H 

27. The acetyl group of acetyl CoA joins the cycle by combining with oxaloacetate, forming citrate The next seven steps decompose the citrate back to oxaloacetate, making the process a cycle The NADH and FADH 2 produced by the cycle relay electrons extracted from food to the electron transport chain © 2011 Pearson Education, Inc.

28. Figure 9.12-1 1 Acetyl CoA Citrate Citric acid cycle CoA-SH Oxaloacetate

29. Figure 9.12-2 1 Acetyl CoA Citrate Isocitrate Citric acid cycle H2OH2O 2 CoA-SH Oxaloacetate

30. Figure 9.12-3 1 Acetyl CoA Citrate Isocitrate  -Ketoglutarate Citric acid cycle NADH + H  NAD  H2OH2O 32 CoA-SH CO2CO2 Oxaloacetate

31. Figure 9.12-4 1 Acetyl CoA Citrate Isocitrate  -Ketoglutarate Succinyl CoA Citric acid cycle NADH + H  NAD  H2OH2O 324 CoA-SH CO2CO2 CO2CO2 Oxaloacetate

32. Figure 9.12-5 1 Acetyl CoA Citrate Isocitrate  -Ketoglutarate Succinyl CoA Succinate Citric acid cycle NADH ATP + H  NAD  H2OH2O ADP GTPGDP P i 3245 CoA-SH CO2CO2 CO2CO2 Oxaloacetate

33. Figure 9.12-6 1 Acetyl CoA Citrate Isocitrate  -Ketoglutarate Succinyl CoA Succinate Fumarate Citric acid cycle NADH FADH 2 ATP + H  NAD  H2OH2O ADP GTPGDP P i FAD 32456 CoA-SH CO2CO2 CO2CO2 Oxaloacetate

34. Figure 9.12-7 1 Acetyl CoA Citrate Isocitrate  -Ketoglutarate Succinyl CoA Succinate Fumarate Malate Citric acid cycle NADH FADH 2 ATP + H  NAD  H2OH2O H2OH2O ADP GTPGDP P i FAD 324567 CoA-SH CO2CO2 CO2CO2 Oxaloacetate

35. Figure 9.12-8 NADH 1 Acetyl CoA Citrate Isocitrate  -Ketoglutarate Succinyl CoA Succinate Fumarate Malate Citric acid cycle NAD  NADH FADH 2 ATP + H  NAD  H2OH2O H2OH2O ADP GTPGDP P i FAD 3245678 CoA-SH CO2CO2 CO2CO2 Oxaloacetate

36. Figure 9.12a Acetyl CoA Oxaloacetate Citrate Isocitrate H2OH2O CoA-SH 1 2

37. Figure 9.12b Isocitrate  -Ketoglutarate Succinyl CoA NADH NAD  + H  CoA-SH CO2CO2 CO2CO2 34 + H 

38. Figure 9.12c Fumarate FADH 2 CoA-SH 6 Succinate Succinyl CoA FAD ADP GTPGDP P i ATP 5

39. Figure 9.12d Oxaloacetate 8 Malate Fumarate H2OH2O NADH NAD  + H  7

40. Electron Transport Chain The electron transport chain is in the inner membrane (cristae) of the mitochondrion Following glycolysis and the citric acid cycle, NADH and FADH 2 account for most of the energy extracted from food These two electron carriers donate electrons to the electron transport chain, which powers ATP synthesis via oxidative phosphorylation © 2011 Pearson Education, Inc.

41. The Pathway of Electron Transport Most of the chain’s components are proteins, The carriers alternate reduced and oxidized states as they accept and donate electrons Electrons drop in free energy as they go down the chain and are finally passed to O 2, forming H 2 O Electrons are passed through a number of proteins including cytochromes (each with an iron atom) to O 2 © 2011 Pearson Education, Inc.

42. Figure 9.13 NADH FADH 2 2 H  + 1 / 2 O 2 2 e  H2OH2O NAD  Multiprotein complexes (originally from NADH or FADH 2 ) I II III IV 50 40 30 20 10 0 Free energy (G) relative to O 2 (kcal/mol) FMN Fe  S FAD Q Cyt b Cyt c 1 Cyt c Cyt a Cyt a 3 Fe  S

43. Chemiosmosis: ATP production through H + Electron transfer causes proteins to pump H + from the mitochondrial matrix to the intermembrane space H + then moves back across the membrane, passing through the proton, ATP synthase ATP synthase uses the exergonic flow of H + to drive phosphorylation of ATP © 2011 Pearson Education, Inc.

44. Figure 9.14 INTERMEMBRANE SPACE Rotor Stator HH Internal rod Catalytic knob ADP + P i ATP MITOCHONDRIAL MATRIX

45. Figure 9.15 Protein complex of electron carriers (carrying electrons from food) Electron transport chain Oxidative phosphorylation Chemiosmosis ATP synth- ase I II III IV Q Cyt c FAD FADH 2 NADH ADP  P i NAD  HH 2 H  + 1 / 2 O 2 HH HH HH 21 HH H2OH2O ATP

46. An Accounting of ATP Production by Cellular Respiration glucose  NADH  electron transport chain  ATP About 30-32 total ATP are made (26/28 via ETC and 4 via substrate level) Takes energy to move ATP into cytosol after it is made, takes E to move pyruvate in Depends on shuttle systems that bring the NADH electrons into the mitochondria © 2011 Pearson Education, Inc.

47. Figure 9.16 Electron shuttles span membrane MITOCHONDRION 2 NADH 6 NADH 2 FADH 2 or  2 ATP  about 26 or 28 ATP Glycolysis Glucose 2 Pyruvate Pyruvate oxidation 2 Acetyl CoA Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis CYTOSOL Maximum per glucose: About 30 or 32 ATP

48. Anaerobic respiration - Fermentation Most cellular respiration requires O 2 to produce ATP Without O 2, no electron transport chain Fermentation uses substrate-level phosphorylation instead of an electron transport chain to generate ATP © 2011 Pearson Education, Inc.

49. Types of Fermentation Fermentation consists of glycolysis plus reactions that regenerate NAD +, which can be reused by glycolysis Two common types are alcohol fermentation and lactic acid fermentation © 2011 Pearson Education, Inc.

50. In alcohol fermentation, pyruvate is converted to ethanol in two steps, with the first releasing CO 2 Alcohol fermentation by yeast is used in brewing, winemaking, and baking © 2011 Pearson Education, Inc.

51. Animation: Fermentation Overview Right-click slide / select “Play”

52. Figure 9.17 2 ADP 2 ATP Glucose Glycolysis 2 Pyruvate 2 CO 2 2  2 NADH 2 Ethanol 2 Acetaldehyde (a) Alcohol fermentation (b) Lactic acid fermentation 2 Lactate 2 Pyruvate 2 NADH Glucose Glycolysis 2 ATP 2 ADP  2 P i NAD 2 H   2 P i 2 NAD    2 H 

53. In lactic acid fermentation, pyruvate is reduced to NADH, forming lactate as an end product, with no release of CO 2 Lactic acid fermentation by some fungi and bacteria is used to make cheese and yogurt Human muscle cells use lactic acid fermentation to generate ATP when O 2 is scarce © 2011 Pearson Education, Inc.

54. Comparing Fermentation with Anaerobic and Aerobic Respiration All use glycolysis (net ATP = 2) to oxidize glucose and harvest chemical energy of food In all three, NAD + is the oxidizing agent that accepts electrons during glycolysis The processes have different final electron acceptors: an organic molecule (such as pyruvate or acetaldehyde) in fermentation and O 2 in cellular respiration Cellular respiration produces 32 ATP per glucose molecule; fermentation produces 2 ATP per glucose molecule © 2011 Pearson Education, Inc.

55. Obligate anaerobes carry out fermentation or anaerobic respiration and cannot survive in the presence of O 2 Yeast and many bacteria are facultative anaerobes, meaning that they can survive using either fermentation or cellular respiration © 2011 Pearson Education, Inc.

56. Figure 9.18 Glucose CYTOSOL Glycolysis Pyruvate No O 2 present: Fermentation O 2 present: Aerobic cellular respiration Ethanol, lactate, or other products Acetyl CoA MITOCHONDRION Citric acid cycle

57. The Evolutionary Significance of Glycolysis Ancient prokaryotes are thought to have used glycolysis long before there was oxygen in the atmosphere Very little O 2 was available in the atmosphere until about 2.7 billion years ago, so early prokaryotes likely used only glycolysis to generate ATP Glycolysis is a very ancient process © 2011 Pearson Education, Inc.

58. Getting E from other sources electrons from many kinds of organic molecules funnel into cellular respiration Proteins must be digested to amino acids; amino groups can feed glycolysis or the citric acid cycle © 2011 Pearson Education, Inc.

59. Fats are digested to glycerol (used in glycolysis) and fatty acids (used in generating acetyl CoA) Fatty acids are broken down by beta oxidation and yield acetyl CoA An oxidized gram of fat produces more than twice as much ATP as an oxidized gram of carbohydrate © 2011 Pearson Education, Inc.

60. Figure 9.19 Carbohydrates Proteins Fatty acids Amino acids Sugars Fats Glycerol Glycolysis Glucose Glyceraldehyde 3- P NH 3 Pyruvate Acetyl CoA Citric acid cycle Oxidative phosphorylation

61. Regulation of Cellular Respiration via Feedback Mechanisms If ATP concentration begins to drop, respiration speeds up; when there is plenty of ATP, respiration slows down © 2011 Pearson Education, Inc.

62. Figure 9.20 Phosphofructokinase Glucose Glycolysis AMP Stimulates    Fructose 6-phosphate Fructose 1,6-bisphosphate Pyruvate Inhibits ATPCitrate Citric acid cycle Oxidative phosphorylation Acetyl CoA