1. CAMPBELL BIOLOGY IN FOCUS © 2014 Pearson Education, Inc. Urry Cain Wasserman Minorsky Jackson Reece Lecture Presentations by Kathleen Fitzpatrick and Nicole Tunbridge 7 Cellular Respiration and Fermentation

2. Overview: Life Is Work  Living cells require energy from outside sources  Some animals, such as the giraffe, obtain energy by eating plants, and some animals feed on other organisms that eat plants © 2014 Pearson Education, Inc.

3.  Energy flows into an ecosystem as sunlight and leaves as heat  Photosynthesis generates O 2 and organic molecules, which are used as fuel for cellular respiration  Cells use chemical energy stored in organic molecules to regenerate ATP, which powers work © 2014 Pearson Education, Inc. Animation: Carbon Cycle

4. © 2014 Pearson Education, Inc. Figure 7.2 Light energy ECOSYSTEM Photosynthesis in chloroplasts CO 2  H 2 O Cellular respiration in mitochondria Organic molecules  O2 O2 ATP ATP powers most cellular work Heat energy

5. Concept 7.1: Catabolic pathways yield energy by oxidizing organic fuels  Several processes are central to cellular respiration and related pathways © 2014 Pearson Education, Inc.

6. Catabolic Pathways and Production of ATP  The breakdown of organic molecules is exergonic  Fermentation is a partial degradation of sugars that occurs without O 2  Aerobic respiration consumes organic molecules and O 2 and yields ATP  Anaerobic respiration is similar to aerobic respiration but consumes compounds other than O 2 © 2014 Pearson Education, Inc.

7.  Cellular respiration includes both aerobic and anaerobic respiration but is often used to refer to aerobic respiration  Although carbohydrates, fats, and proteins are all consumed as fuel, it is helpful to trace cellular respiration with the sugar glucose C 6 H 12 O 6  6 O 2  6 CO 2  6 H 2 O  Energy (ATP  heat) © 2014 Pearson Education, Inc.

8. Redox Reactions: Oxidation and Reduction  The transfer of electrons during chemical reactions releases energy stored in organic molecules  This released energy is ultimately used to synthesize ATP © 2014 Pearson Education, Inc.

9. The Principle of Redox  Chemical reactions that transfer electrons between reactants are called oxidation-reduction reactions, or redox reactions  In oxidation, a substance loses electrons, or is oxidized  In reduction, a substance gains electrons, or is reduced (the amount of positive charge is reduced) © 2014 Pearson Education, Inc.

10. Figure 7.UN01 becomes oxidized (loses electron) becomes reduced (gains electron)

11. © 2014 Pearson Education, Inc. Figure 7.UN02 becomes oxidized becomes reduced

12.  The electron donor is called the reducing agent  The electron acceptor is called the oxidizing agent  Some redox reactions do not transfer electrons but change the electron sharing in covalent bonds  An example is the reaction between methane and O 2 © 2014 Pearson Education, Inc.

13. Figure 7.3 Reactants Products Methane (reducing agent) Oxygen (oxidizing agent) Carbon dioxide Water becomes reduced becomes oxidized

14.  Redox reactions that move electrons closer to electronegative atoms, like oxygen, release chemical energy that can be put to work © 2014 Pearson Education, Inc.

15. Oxidation of Organic Fuel Molecules During Cellular Respiration  During cellular respiration, the fuel (such as glucose) is oxidized, and O 2 is reduced  Organic molecules with an abundance of hydrogen, like carbohydrates and fats, are excellent fuels  As hydrogen (with its electron) is transferred to oxygen, energy is released that can be used in ATP sythesis © 2014 Pearson Education, Inc.

16. Figure 7.UN03 becomes oxidized becomes reduced

17. Stepwise Energy Harvest via NAD + and the Electron Transport Chain  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 is tapped to synthesize ATP © 2014 Pearson Education, Inc.

18. Figure 7.4 NAD  Nicotinamide (oxidized form) Nicotinamide (reduced form) Oxidation of NADH Reduction of NAD  Dehydrogenase NADH  2[H] (from food) 2 e −  2 H  2 e −  H  HH HH 

19. © 2014 Pearson Education, Inc. Figure 7.UN04

20.  NADH passes the electrons to the electron transport chain  Unlike an uncontrolled reaction, the electron transport chain passes electrons in a series of steps instead of one explosive reaction  O 2 pulls electrons down the chain in an energy- yielding tumble  The energy yielded is used to regenerate ATP © 2014 Pearson Education, Inc.

21. Figure 7.5 Explosive release (a) Uncontrolled reaction (b) Cellular respiration H2OH2O Free energy, G Electron transport chain Controlled release of energy H2OH2O 2 H  2 e − 2 H   2 e − ATP ½ ½ ½ H 2  O2O2 O2O2 O2O2 2 H 

22. The Stages of Cellular Respiration: A Preview  Harvesting of energy from glucose has three stages  Glycolysis (breaks down glucose into two molecules of pyruvate)  Pyruvate oxidation and the citric acid cycle (completes the breakdown of glucose)  Oxidative phosphorylation (accounts for most of the ATP synthesis) © 2014 Pearson Education, Inc. Animation: Cellular Respiration

23. © 2014 Pearson Education, Inc. Figure 7.UN05 Glycolysis (color-coded teal throughout the chapter) Pyruvate oxidation and the citric acid cycle (color-coded salmon) 1. Oxidative phosphorylation: electron transport and chemiosmosis (color-coded violet) 2. 3.

24. © 2014 Pearson Education, Inc. Figure 7.6-1 Electrons via NADH Glycolysis GlucosePyruvate CYTOSOL ATP Substrate-level MITOCHONDRION

25. © 2014 Pearson Education, Inc. Figure 7.6-2 Electrons via NADH Glycolysis GlucosePyruvate oxidation Acetyl CoA Citric acid cycle Electrons via NADH and FADH 2 CYTOSOL ATP Substrate-level ATP Substrate-level MITOCHONDRION

26. © 2014 Pearson Education, Inc. Figure 7.6-3 Electrons via NADH Glycolysis GlucosePyruvate oxidation Acetyl CoA Citric acid cycle Electrons via NADH and FADH 2 Oxidative phosphorylation: electron transport and chemiosmosis CYTOSOL ATP Substrate-level ATP Substrate-level MITOCHONDRION ATP Oxidative

27.  The process that generates most of the ATP is called oxidative phosphorylation because it is powered by redox reactions © 2014 Pearson Education, Inc.

28.  Oxidative phosphorylation accounts for almost 90% of the ATP generated by cellular respiration  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 © 2014 Pearson Education, Inc.

29. Figure 7.7 Substrate P ADP Product ATP  Enzyme

30. Concept 7.2: Glycolysis harvests chemical energy by oxidizing glucose to pyruvate  Glycolysis (“sugar splitting”) 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 © 2014 Pearson Education, Inc.

31. Figure 7.UN06 Glycolysis Pyruvate oxidation Citric acid cycle Oxidative phosphorylation ATP

32. © 2014 Pearson Education, Inc. Figure 7.8 Energy Investment Phase Energy Payoff Phase Net Glucose 2 ADP  2 P 4 ADP  4 P 2 NAD   4 e −  4 H  4 ATP formed − 2 ATP used 2 ATP 4 ATP used formed 2 NADH  2 H  2 Pyruvate  2 H 2 O 2 NADH  2 H  2 ATP

33. © 2014 Pearson Education, Inc. Figure 7.9a Glycolysis: Energy Investment Phase Glucose ATP ADP Glucose 6-phosphate Phosphogluco- isomerase Hexokinase 1234 ATP ADP Fructose 6-phosphate Phospho- fructokinase Fructose 1,6-bisphosphate Aldolase Isomerase 5 Glyceraldehyde 3-phosphate (G3P) Dihydroxyacetone phosphate (DHAP)

34. © 2014 Pearson Education, Inc. Figure 7.9aa-1 Glycolysis: Energy Investment Phase Glucose

35. © 2014 Pearson Education, Inc. Figure 7.9aa-2 Glycolysis: Energy Investment Phase Glucose 6-phosphate ADP ATP Hexokinase 1

36. © 2014 Pearson Education, Inc. Figure 7.9aa-3 Glycolysis: Energy Investment Phase Glucose 6-phosphate ADP ATP Hexokinase 1 Fructose 6-phosphate Phosphogluco- isomerase 2

37. © 2014 Pearson Education, Inc. Figure 7.9ab-1 Glycolysis: Energy Investment Phase Fructose 6-phosphate

38. © 2014 Pearson Education, Inc. Figure 7.9ab-2 Glycolysis: Energy Investment Phase Fructose 6-phosphate Phospho- fructokinase 3 Fructose 1,6-bisphosphate ATP ADP

39. © 2014 Pearson Education, Inc. Figure 7.9ab-3 Glycolysis: Energy Investment Phase Fructose 6-phosphate Phospho- fructokinase 3 Aldolase Isomerase 45 Fructose 1,6-bisphosphate Glyceraldehyde 3-phosphate (G3P) ATP ADP Dihydroxyacetone phosphate (DHAP)

40. © 2014 Pearson Education, Inc. Figure 7.9b Glycolysis: Energy Payoff Phase 2 NAD  Glyceraldehyde 3-phosphate (G3P) Triose phosphate dehydrogenase 6  2 H  2 NADH 2 2 P i 1,3-Bisphospho- glycerate 3-Phospho- glycerate 2-Phospho- glycerate Phosphoenol- pyruvate (PEP) Pyruvate Phospho- glycerokinase Phospho- glyceromutase Enolase Pyruvate kinase 2 ADP 2 2 2 2 2 ATP 2 H 2 O 2 ATP 9 10 8 7

41. © 2014 Pearson Education, Inc. Figure 7.9ba-1 Isomerase 4 Glyceraldehyde 3-phosphate (G3P) Dihydroxyacetone phosphate (DHAP) Glycolysis: Energy Payoff Phase Aldolase 5

42. © 2014 Pearson Education, Inc. Figure 7.9ba-2 Isomerase Glyceraldehyde 3-phosphate (G3P) Dihydroxyacetone phosphate (DHAP) Glycolysis: Energy Payoff Phase 2 NAD  Triose phosphate dehydrogenase  2 H  2 NADH 2 1,3-Bisphospho- glycerate 2 Aldolase P i 5 6 4

43. © 2014 Pearson Education, Inc. Figure 7.9ba-3 Isomerase Glyceraldehyde 3-phosphate (G3P) Dihydroxyacetone phosphate (DHAP) Glycolysis: Energy Payoff Phase 2 NAD  Triose phosphate dehydrogenase  2 H  2 NADH 2 1,3-Bisphospho- glycerate 3-Phospho- glycerate Phospho- glycerokinase 2 ADP 2 ATP 2 Aldolase P i 2 5 7 6 4

44. © 2014 Pearson Education, Inc. Figure 7.9bb-1 3-Phospho- glycerate Glycolysis: Energy Payoff Phase 2

45. © 2014 Pearson Education, Inc. Figure 7.9bb-2 8 3-Phospho- glycerate Glycolysis: Energy Payoff Phase Phospho- glyceromutase 2 2 2 2 H 2 O 2-Phospho- glycerate Phosphoenol- pyruvate (PEP) Enolase 9

46. © 2014 Pearson Education, Inc. Figure 7.9bb-3 3-Phospho- glycerate Glycolysis: Energy Payoff Phase 2 ATP Phospho- glyceromutase 2 2 2 2 2 ADP 2 H 2 O 2-Phospho- glycerate Phosphoenol- pyruvate (PEP) Pyruvate EnolasePyruvate kinase 9 10 8

47. Concept 7.3: After pyruvate is oxidized, the citric acid cycle completes the energy-yielding oxidation of organic molecules  In the presence of O 2, pyruvate enters the mitochondrion (in eukaryotic cells), where the oxidation of glucose is completed  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 © 2014 Pearson Education, Inc.

48. Figure 7.UN07 Glycolysis Pyruvate oxidation Citric acid cycle Oxidative phosphorylation ATP

49. © 2014 Pearson Education, Inc. Figure 7.10 CYTOSOL Pyruvate (from glycolysis, 2 molecules per glucose) CO 2 CoA NAD  NADH MITOCHONDRION CoA Acetyl CoA  H  Citric acid cycle FADH 2 FAD ADP  P i ATP NADH 3 NAD  3  3 H  2 CO 2

50.  The citric acid cycle, also called the Krebs cycle, completes the breakdown of pyruvate to CO 2  The cycle oxidizes organic fuel derived from pyruvate, generating 1 ATP, 3 NADH, and 1 FADH 2 per turn © 2014 Pearson Education, Inc.

51. Figure 7.UN08 Glycolysis Pyruvate oxidation Oxidative phosphorylation ATP Citric acid cycle

52. © 2014 Pearson Education, Inc. Figure 7.11-1 Acetyl CoA Oxaloacetate CoA-SH Citrate H2OH2O Isocitrate Citric acid cycle 2 1

53. © 2014 Pearson Education, Inc. Figure 7.11-2 Acetyl CoA Oxaloacetate Citrate H2OH2O Isocitrate NADH NAD   H  CO2CO2  -Ketoglutarate Citric acid cycle 3 1 CoA-SH 2

54. © 2014 Pearson Education, Inc. Figure 7.11-3 Acetyl CoA Oxaloacetate Citrate H2OH2O Isocitrate NADH NAD   H  CO2CO2  -Ketoglutarate Citric acid cycle CoA-SH CO2CO2 NAD  NADH  H  Succinyl CoA 4 1 3 CoA-SH 2

55. © 2014 Pearson Education, Inc. Figure 7.11-4 Acetyl CoA Oxaloacetate Citrate H2OH2O Isocitrate NADH NAD   H  CO2CO2  -Ketoglutarate Citric acid cycle CoA-SH CO2CO2 NAD  NADH  H  ATP formation Succinyl CoA ADP GDP GTP P i ATP Succinate 5 4 1 CoA-SH 3 2

56. © 2014 Pearson Education, Inc. Figure 7.11-5 Malate Succinate FAD FADH 2 Fumarate H2OH2O 7 6 Acetyl CoA Oxaloacetate Citrate H2OH2O Isocitrate NADH NAD   H  CO2CO2  -Ketoglutarate Citric acid cycle CoA-SH CO2CO2 NAD  NADH  H  ATP formation Succinyl CoA ADP GDP GTP P i ATP 5 4 1 CoA-SH 3 2

57. © 2014 Pearson Education, Inc. Figure 7.11-6 NADH NAD   H  8 Malate Succinate FAD FADH 2 Fumarate H2OH2O 7 6 Acetyl CoA Oxaloacetate Citrate H2OH2O Isocitrate NADH NAD   H  CO2CO2  -Ketoglutarate Citric acid cycle CoA-SH CO2CO2 NAD  NADH  H  ATP formation Succinyl CoA ADP GDP GTP P i ATP 5 4 1 CoA-SH 3 2

58. © 2014 Pearson Education, Inc. Figure 7.11a CoA-SH Acetyl CoA Start: Acetyl CoA adds its two-carbon group to oxaloacetate, producing citrate; this is a highly exergonic reaction. Oxaloacetate Citrate Isocitrate H2OH2O 1 2

59. © 2014 Pearson Education, Inc. Figure 7.11b Isocitrate Redox reaction: Isocitrate is oxidized; NAD  is reduced. Redox reaction: After CO 2 release, the resulting four-carbon molecule is oxidized (reducing NAD  ), then made reactive by addition of CoA. CO 2 release  -Ketoglutarate Succinyl CoA NAD  NADH  H  CO2CO2 CO2CO2 CoA-SH NAD  NADH  H  3 4

60. © 2014 Pearson Education, Inc. Figure 7.11c CoA-SH Redox reaction: Succinate is oxidized; FAD is reduced. Fumarate Succinate Succinyl CoA ATP formation ATP ADP GDP GTP FAD FADH 2 P i 5 6

61. © 2014 Pearson Education, Inc. Figure 7.11d Redox reaction: Malate is oxidized; NAD  is reduced. Fumarate Malate Oxaloacetate H2OH2O NAD   H  NADH 7 8

62.  The citric acid cycle has eight steps, each catalyzed by a specific enzyme  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 © 2014 Pearson Education, Inc.

63. Concept 7.4: During oxidative phosphorylation, chemiosmosis couples electron transport to ATP synthesis  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 © 2014 Pearson Education, Inc.

64. The Pathway of Electron Transport  The electron transport chain is in the inner membrane (cristae) of the mitochondrion  Most of the chain’s components are proteins, which exist in multiprotein complexes  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 © 2014 Pearson Education, Inc.

65. Figure 7.UN09 Glycolysis Pyruvate oxidation Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis ATP

66. © 2014 Pearson Education, Inc. Figure 7.12 Multiprotein complexes (originally from NADH or FADH 2 ) Free energy (G) relative to O 2 (kcal/mol) 50 40 30 20 10 0 NADH NAD  FADH 2 FAD 2 2 e−e− e−e− FMN Fe S Q I II III Cyt b Cyt c 1 Fe S Cyt c IV Cyt a Cyt a 3 2 e−e− O2O2 2 H   ½ H2OH2O

67.  Electrons are transferred from NADH or FADH 2 to the electron transport chain  Electrons are passed through a number of proteins including cytochromes (each with an iron atom) to O 2  The electron transport chain generates no ATP directly  It breaks the large free-energy drop from food to O 2 into smaller steps that release energy in manageable amounts © 2014 Pearson Education, Inc.

68. Chemiosmosis: The Energy-Coupling Mechanism  Electron transfer in the electron transport chain causes proteins to pump H  from the mitochondrial matrix to the intermembrane space  H  then moves back across the membrane, passing through the protein complex, ATP synthase  ATP synthase uses the exergonic flow of H  to drive phosphorylation of ATP  This is an example of chemiosmosis, the use of energy in a H  gradient to drive cellular work © 2014 Pearson Education, Inc.

69. Video: ATP Synthase 3-D Side View Video: ATP Synthase 3-D Top View

70. © 2014 Pearson Education, Inc. Figure 7.13 INTERMEMBRANE SPACE MITOCHONDRIAL MATRIX Rotor Internal rod Catalytic knob Stator HH ATP ADP P i 

71.  The energy stored in a H  gradient across a membrane couples the redox reactions of the electron transport chain to ATP synthesis  The H  gradient is referred to as a proton-motive force, emphasizing its capacity to do work © 2014 Pearson Education, Inc.

72. Figure 7.UN09 Glycolysis Pyruvate oxidation Citric acid cycle Oxidative phosphorylation: electron transport and chemiosmosis ATP

73. © 2014 Pearson Education, Inc. Figure 7.14 Protein complex of electron carriers HH HH HH HH Q I II III FADH 2 FAD NAD  NADH (carrying electrons from food) Electron transport chain Oxidative phosphorylation Chemiosmosis ATP synthase HH ADP  ATP P i H2OH2O 2 H   ½ O 2 IV Cyt c 1 2

74. An Accounting of ATP Production by Cellular Respiration  During cellular respiration, most energy flows in the following sequence: glucose  NADH  electron transport chain  proton-motive force  ATP  About 34% of the energy in a glucose molecule is transferred to ATP during cellular respiration, making about 32 ATP  There are several reasons why the number of ATP molecules is not known exactly © 2014 Pearson Education, Inc.

75. Figure 7.15 Electron shuttles span membrane CYTOSOL 2 NADH 2 FADH 2 or 2 NADH Glycolysis Glucose 2 Pyruvate oxidation 2 Acetyl CoA Citric acid cycle 6 NADH2 FADH 2 Oxidative phosphorylation: electron transport and chemiosmosis  about 26 or 28 ATP  2 ATP About 30 or 32 ATP Maximum per glucose: MITOCHONDRION

76. Concept 7.5: Fermentation and anaerobic respiration enable cells to produce ATP without the use of oxygen  Most cellular respiration requires O 2 to produce ATP  Without O 2, the electron transport chain will cease to operate  In that case, glycolysis couples with fermentation or anaerobic respiration to produce ATP © 2014 Pearson Education, Inc.

77.  Anaerobic respiration uses an electron transport chain with a final electron acceptor other than O 2, for example, sulfate  Fermentation uses substrate-level phosphorylation instead of an electron transport chain to generate ATP © 2014 Pearson Education, Inc.

78. 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 © 2014 Pearson Education, Inc.

79.  In alcohol fermentation, pyruvate is converted to ethanol in two steps  The first step releases CO 2 from pyruvate, and the second step reduces acetaldehyde to ethanol  Alcohol fermentation by yeast is used in brewing, winemaking, and baking © 2014 Pearson Education, Inc. Animation: Fermentation Overview

80. © 2014 Pearson Education, Inc. Figure 7.16 2 ADP  2 2 ATP P i Glucose Glycolysis 2 Pyruvate 2 CO 2 2 NADH  2 H  2 NAD  2 Ethanol (a) Alcohol fermentation 2 Acetaldehyde (b) Lactic acid fermentation 2 Lactate 2 NADH  2 H  2 NAD  2 Pyruvate Glycolysis 2 ATP 2 ADP  2 P i Glucose

81.  In lactic acid fermentation, pyruvate is reduced by 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 © 2014 Pearson Education, Inc.

82. 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 © 2014 Pearson Education, Inc.

83.  Obligate anaerobes carry out only 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  In a facultative anaerobe, pyruvate is a fork in the metabolic road that leads to two alternative catabolic routes © 2014 Pearson Education, Inc.

84. Figure 7.17 Glucose CYTOSOL Glycolysis Pyruvate O 2 present: Aerobic cellular respiration No O 2 present: Fermentation Ethanol, lactate, or other products Acetyl CoA Citric acid cycle MITOCHONDRION

85. 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 © 2014 Pearson Education, Inc.

86. Concept 7.6: Glycolysis and the citric acid cycle connect to many other metabolic pathways  Gycolysis and the citric acid cycle are major intersections to various catabolic and anabolic pathways © 2014 Pearson Education, Inc.

87. The Versatility of Catabolism  Catabolic pathways funnel electrons from many kinds of organic molecules into cellular respiration  Glycolysis accepts a wide range of carbohydrates  Proteins must be digested to amino acids and amino groups must be removed before amino acids can feed glycolysis or the citric acid cycle © 2014 Pearson Education, Inc.

88.  Fats are digested to glycerol (used in glycolysis) and fatty acids  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 © 2014 Pearson Education, Inc.

89. Figure 7.18-5 Proteins Amino acids Carbohydrates Sugars Glucose Glycolysis Glyceraldehyde 3- Pyruvate P Acetyl CoA Citric acid cycle NH 3 Fats Glycerol Fatty acids Oxidative phosphorylation

90. Biosynthesis (Anabolic Pathways)  The body uses small molecules to build other substances  Some of these small molecules come directly from food; others can be produced during glycolysis or the citric acid cycle © 2014 Pearson Education, Inc.