1. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Human Anatomy & Physiology SEVENTH EDITION Elaine N. Marieb Katja Hoehn PowerPoint ® Lecture Slides prepared by Vince Austin, Bluegrass Technical and Community College C H A P T E R 24 Nutrition, Metabolism, and Body Temperature Regulation P A R T A

2. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Nutrition  Nutrient – a substance that promotes normal growth, maintenance, and repair  Major nutrients – carbohydrates, lipids, and proteins  Other nutrients – vitamins and minerals (and technically speaking, water)

3. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings USDA Food Guide Pyramid Figure 24.1a

4. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Nutrition Figure 24.1b

5. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Carbohydrates  Complex carbohydrates (starches) are found in bread, cereal, flour, pasta, nuts, and potatoes  Simple carbohydrates (sugars) are found in soft drinks, candy, fruit, and ice cream

6. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Carbohydrates  Glucose is the molecule ultimately used by body cells to make ATP  Neurons and RBCs rely almost entirely upon glucose to supply their energy needs  Excess glucose is converted to glycogen or fat and stored

7. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Carbohydrates  The minimum amount of carbohydrates needed to maintain adequate blood glucose levels is 100 grams per day  Starchy foods and milk have nutrients such as vitamins and minerals in addition to complex carbohydrates  Refined carbohydrate foods (candy and soft drinks) provide energy sources only and are referred to as “empty calories”

8. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Lipids  The most abundant dietary lipids, triglycerides, are found in both animal and plant foods  Essential fatty acids – linoleic and linolenic acid, found in most vegetables, must be ingested  Dietary fats:  Help the body to absorb vitamins  Are a major energy fuel of hepatocytes and skeletal muscle  Are a component of myelin sheaths and all cell membranes

9. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Lipids  Fatty deposits in adipose tissue provide:  A protective cushion around body organs  An insulating layer beneath the skin  An easy-to-store concentrated source of energy

10. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Lipids  Prostaglandins function in:  Smooth muscle contraction  Control of blood pressure  Inflammation  Cholesterol stabilizes membranes and is a precursor of bile salts and steroid hormones

11. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Lipids: Dietary Requirements  Higher for infants and children than for adults  The American Heart Association suggests that:  Fats should represent less than 30% of one’s total caloric intake  Saturated fats should be limited to 10% or less of one’s total fat intake  Daily cholesterol intake should not exceed 200 mg

12. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Proteins  Complete proteins that meet all the body’s amino acid needs are found in eggs, milk, milk products, meat, and fish  Incomplete proteins are found in legumes, nuts, seeds, grains, and vegetables

13. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Proteins  Proteins supply:  Essential amino acids, the building blocks for nonessential amino acids  Nitrogen for nonprotein nitrogen-containing substances  Daily intake should be approximately 0.8g/kg of body weight

14. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Proteins: Synthesis and Hydrolysis  All-or-none rule  All amino acids needed must be present at the same time for protein synthesis to occur  Adequacy of caloric intake  Protein will be used as fuel if there is insufficient carbohydrate or fat available

15. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Proteins: Synthesis and Hydrolysis  Nitrogen balance  The rate of protein synthesis equals the rate of breakdown and loss  Positive – synthesis exceeds breakdown (normal in children and tissue repair)  Negative – breakdown exceeds synthesis (e.g., stress, burns, infection, or injury)  Hormonal control  Anabolic hormones accelerate protein synthesis

16. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Essential Amino Acids Figure 24.2

17. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Vitamins  Organic compounds needed for growth and good health  They are crucial in helping the body use nutrients and often function as coenzymes  Only vitamins D, K, and B are synthesized in the body; all others must be ingested  Water-soluble vitamins (B-complex and C) are absorbed in the gastrointestinal tract  B 12 additionally requires gastric intrinsic factor to be absorbed

18. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Vitamins  Fat-soluble vitamins (A, D, E, and K) bind to ingested lipids and are absorbed with their digestion products  Vitamins A, C, and E also act in an antioxidant cascade

19. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Minerals  Seven minerals are required in moderate amounts  Calcium, phosphorus, potassium, sulfur, sodium, chloride, and magnesium  Dozens are required in trace amounts  Minerals work with nutrients to ensure proper body functioning  Calcium, phosphorus, and magnesium salts harden bone

20. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Minerals  Sodium and chloride help maintain normal osmolarity, water balance, and are essential in nerve and muscle function  Uptake and excretion must be balanced to prevent toxic overload

21. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Metabolism  Metabolism – all chemical reactions necessary to maintain life  Cellular respiration – food fuels are broken down within cells and some of the energy is captured to produce ATP  Anabolic reactions – synthesis of larger molecules from smaller ones  Catabolic reactions – hydrolysis of complex structures into simpler ones

22. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Metabolism  Enzymes shift the high-energy phosphate groups of ATP to other molecules  These phosphorylated molecules are activated to perform cellular functions

23. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Stages of Metabolism  Energy-containing nutrients are processed in three major stages  Digestion – breakdown of food; nutrients are transported to tissues  Anabolism and formation of catabolic intermediates where nutrients are:  Built into lipids, proteins, and glycogen  Broken down by catabolic pathways to pyruvic acid and acetyl CoA  Oxidative breakdown – nutrients are catabolized to carbon dioxide, water, and ATP

24. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 24.3

25. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Oxidation-Reduction (Redox) Reactions  Oxidation occurs via the gain of oxygen or the loss of hydrogen  Whenever one substance is oxidized, another substance is reduced  Oxidized substances lose energy  Reduced substances gain energy  Coenzymes act as hydrogen (or electron) acceptors  Two important coenzymes are nicotinamide adenine dinucleotide (NAD + ) and flavin adenine dinucleotide (FAD)

26. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Mechanisms of ATP Synthesis: Substrate-Level Phosphorylation  High-energy phosphate groups are transferred directly from phosphorylated substrates to ADP  ATP is synthesized via substrate-level phosphorylation in glycolysis and the Krebs cycle Figure 24.4a

27. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Mechanisms of ATP Synthesis: Oxidative Phosphorylation  Uses the chemiosmotic process whereby the movement of substances across a membrane is coupled to chemical reactions

28. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Mechanisms of ATP Synthesis: Oxidative Phosphorylation  Is carried out by the electron transport proteins in the cristae of the mitochondria  Nutrient energy is used to pump hydrogen ions into the intermembrane space  A steep diffusion gradient across the membrane results  When hydrogen ions flow back across the membrane through ATP synthase, energy is captured and attaches phosphate groups to ADP (to make ATP)

29. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Mechanisms of ATP Synthesis: Oxidative Phosphorylation Figure 24.4b

30. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Carbohydrate Metabolism  Since all carbohydrates are transformed into glucose, it is essentially glucose metabolism  Oxidation of glucose is shown by the overall reaction:  C 6 H 12 O 6 + 6O 2  6H 2 O + 6CO 2 + 36 ATP + heat  Glucose is catabolized in three pathways  Glycolysis  Krebs cycle  The electron transport chain and oxidative phosphorylation

31. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Carbohydrate Catabolism Figure 24.5

32. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Glycolysis  A three-phase pathway in which:  Glucose is oxidized into pyruvic acid  NAD + is reduced to NADH + H +  ATP is synthesized by substrate-level phosphorylation  Pyruvic acid:  Moves on to the Krebs cycle in an aerobic pathway  Is reduced to lactic acid in an anaerobic environment

33. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Glycolysis Figure 24.6 2 2 Glucose 4 ADP 2 NAD + 2 Lactic acid NADH+H + 2 Pyruvic acid Phase 1 Sugar activation Fructose-1,6- bisphosphate Dihydroxyacetone phosphate Glyceraldehyde phosphate Phase 2 Sugar cleavage Phase 3 Sugar oxidation and formation of ATP Key: = Carbon atom = Inorganic phosphate O2O2 Glycolysis Electron trans- port chain and oxidative phosphorylation 2 ADP 2 ATP 4 ATP P PP P PiPi PiPi To Krebs cycle (aerobic pathway) ATP Krebs cycle O2O2

34. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Glycolysis: Phase 1 and 2  Phase 1: Sugar activation  Two ATP molecules activate glucose into fructose-1,6-diphosphate  Phase 2: Sugar cleavage  Fructose-1,6-bisphosphate is cleaved into two 3-carbon isomers  Bishydroxyacetone phosphate  Glyceraldehyde 3-phosphate

35. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Glycolysis: Phase 3  Phase 3: Oxidation and ATP formation  The 3-carbon sugars are oxidized (reducing NAD + )  Inorganic phosphate groups (P i ) are attached to each oxidized fragment  The terminal phosphates are cleaved and captured by ADP to form four ATP molecules

36. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Glycolysis: Phase 3  The final products are:  Two pyruvic acid molecules  Two NADH + H + molecules (reduced NAD + )  A net gain of two ATP molecules

37. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Krebs Cycle: Preparatory Step  Occurs in the mitochondrial matrix and is fueled by pyruvic acid and fatty acids

38. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Krebs Cycle: Preparatory Step  Pyruvic acid is converted to acetyl CoA in three main steps:  Decarboxylation  Carbon is removed from pyruvic acid  Carbon dioxide is released

39. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Krebs Cycle: Preparatory Step  Oxidation  Hydrogen atoms are removed from pyruvic acid  NAD + is reduced to NADH + H +  Formation of acetyl CoA – the resulting acetic acid is combined with coenzyme A, a sulfur-containing coenzyme, to form acetyl CoA

40. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Krebs Cycle  An eight-step cycle in which each acetic acid is decarboxylated and oxidized, generating:  Three molecules of NADH + H +  One molecule of FADH 2  Two molecules of CO 2  One molecule of ATP  For each molecule of glucose entering glycolysis, two molecules of acetyl CoA enter the Krebs cycle PLAY Krebs Cycle

41. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 24.7 NAD + GDP + CO 2 NAD + FAD NADH+H + Cytosol Mitochondrion (fluid matrix) FADH 2 NADH+H + Citric acid (initial reactant) (pickup molecule) Oxaloacetic acid Malic acid Fumaric acid Succinic acid Succinyl-CoA GTP ADP PiPi = Carbon atom Key: = Inorganic phosphate = Coenzyme A CoA Acetyl CoA Pyruvic acid from glycolysis Glycolysis Electron transport chain and oxidative phosphorylation Krebs cycle PiPi CoA ATP Krebs cycle NAD + CO 2 NAD + NADH+H + Isocitric acid  -Ketoglutaric acid CoA ATP

42. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 24.7 NAD + CO 2 NADH+H + Cytosol Mitochondrion (fluid matrix) = Carbon atom Key: = Inorganic phosphate = Coenzyme A CoA Acetyl CoA Pyruvic acid from glycolysis Glycolysis Electron transport chain and oxidative phosphorylation Krebs cycle PiPi CoA ATP

43. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 24.7 NAD + CO 2 NADH+H + Cytosol Mitochondrion (fluid matrix) Citric acid (initial reactant) (pickup molecule) Oxaloacetic acid = Carbon atom Key: = Inorganic phosphate = Coenzyme A CoA Acetyl CoA Pyruvic acid from glycolysis Glycolysis Electron transport chain and oxidative phosphorylation Krebs cycle PiPi CoA Krebs cycle ATP

44. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 24.7 NAD + CO 2 NADH+H + Cytosol Mitochondrion (fluid matrix) Citric acid (initial reactant) (pickup molecule) Oxaloacetic acid = Carbon atom Key: = Inorganic phosphate = Coenzyme A CoA Acetyl CoA Pyruvic acid from glycolysis Glycolysis Electron transport chain and oxidative phosphorylation Krebs cycle PiPi CoA Krebs cycle Isocitric acid ATP

45. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 24.7 NAD + CO 2 NADH+H + Cytosol Mitochondrion (fluid matrix) Citric acid (initial reactant) (pickup molecule) Oxaloacetic acid = Carbon atom Key: = Inorganic phosphate = Coenzyme A CoA Acetyl CoA Pyruvic acid from glycolysis Glycolysis Electron transport chain and oxidative phosphorylation Krebs cycle PiPi CoA Krebs cycle NAD + CO 2 NADH+H + Isocitric acid  -Ketoglutaric acid ATP

46. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 24.7 NAD + CO 2 NADH+H + Cytosol Mitochondrion (fluid matrix) Citric acid (initial reactant) (pickup molecule) Oxaloacetic acid Succinyl-CoA = Carbon atom Key: = Inorganic phosphate = Coenzyme A CoA Acetyl CoA Pyruvic acid from glycolysis Glycolysis Electron transport chain and oxidative phosphorylation Krebs cycle PiPi CoA Krebs cycle NAD + CO 2 NAD + NADH+H + Isocitric acid  -Ketoglutaric acid CoA ATP

47. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 24.7 NAD + GDP + CO 2 NADH+H + Cytosol Mitochondrion (fluid matrix) Citric acid (initial reactant) (pickup molecule) Oxaloacetic acid Succinic acid Succinyl-CoA GTP ADP PiPi = Carbon atom Key: = Inorganic phosphate = Coenzyme A CoA Acetyl CoA Pyruvic acid from glycolysis Glycolysis Electron transport chain and oxidative phosphorylation Krebs cycle PiPi CoA ATP Krebs cycle NAD + CO 2 NAD + NADH+H + Isocitric acid  -Ketoglutaric acid CoA ATP

48. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 24.7 NAD + GDP + CO 2 FAD NADH+H + Cytosol Mitochondrion (fluid matrix) FADH 2 Citric acid (initial reactant) (pickup molecule) Oxaloacetic acid Fumaric acid Succinic acid Succinyl-CoA GTP ADP PiPi = Carbon atom Key: = Inorganic phosphate = Coenzyme A CoA Acetyl CoA Pyruvic acid from glycolysis Glycolysis Electron transport chain and oxidative phosphorylation Krebs cycle PiPi CoA ATP Krebs cycle NAD + CO 2 NAD + NADH+H + Isocitric acid  -Ketoglutaric acid CoA ATP

49. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 24.7 NAD + GDP + CO 2 FAD NADH+H + Cytosol Mitochondrion (fluid matrix) FADH 2 Citric acid (initial reactant) (pickup molecule) Oxaloacetic acid Malic acid Fumaric acid Succinic acid Succinyl-CoA GTP ADP PiPi = Carbon atom Key: = Inorganic phosphate = Coenzyme A CoA Acetyl CoA Pyruvic acid from glycolysis Glycolysis Electron transport chain and oxidative phosphorylation Krebs cycle PiPi CoA ATP Krebs cycle NAD + CO 2 NAD + NADH+H + Isocitric acid  -Ketoglutaric acid CoA ATP

50. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 24.7 NAD + GDP + CO 2 NAD + FAD NADH+H + Cytosol Mitochondrion (fluid matrix) FADH 2 NADH+H + Citric acid (initial reactant) (pickup molecule) Oxaloacetic acid Malic acid Fumaric acid Succinic acid Succinyl-CoA GTP ADP PiPi = Carbon atom Key: = Inorganic phosphate = Coenzyme A CoA Acetyl CoA Pyruvic acid from glycolysis Glycolysis Electron transport chain and oxidative phosphorylation Krebs cycle PiPi CoA ATP Krebs cycle NAD + CO 2 NAD + NADH+H + Isocitric acid  -Ketoglutaric acid CoA ATP

51. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Electron Transport Chain  Food (glucose) is oxidized and the released hydrogens:  Are transported by coenzymes NADH and FADH 2  Enter a chain of proteins bound to metal atoms (cofactors)  Combine with molecular oxygen to form water  Release energy  The energy released is harnessed to attach inorganic phosphate groups (P i ) to ADP, making ATP by oxidative phosphorylation

52. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Mechanism of Oxidative Phosphorylation  The hydrogens delivered to the chain are split into protons (H + ) and electrons  The protons are pumped across the inner mitochondrial membrane by:  NADH dehydrogenase (FMN, Fe-S)  Cytochrome b-c 1  Cytochrome oxidase (a-a 3 )  The electrons are shuttled from one acceptor to the next

53. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Mechanism of Oxidative Phosphorylation  Electrons are delivered to oxygen, forming oxygen ions  Oxygen ions attract H + to form water  H + pumped to the intermembrane space:  Diffuses back to the matrix via ATP synthase  Releases energy to make ATP PLAY InterActive Physiology ®: Muscular System: Muscular Metabolism

54. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 24.8 Electron Transport ChainATP Synthase Core ADP + Cyt c Q Intermembrane space Inner mitochondrial membrane Mitochondrial matrix ATP PiPi H+H+ 2H+H+ + H+H+ H+H+ H+H+ H+H+ O2O2 H2OH2O Glycolysis Electron transport chain and oxidative phosphorylation Krebs cycle e- 1212 NADH + H + NAD + FAD (carrying from food) e- FADH 2 e- ATP 3 2 1

55. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 24.8 Electron Transport Chain Core Cyt c Q Intermembrane space Inner mitochondrial membrane Mitochondrial matrix H+H+ Glycolysis Electron transport chain and oxidative phosphorylation Krebs cycle NADH + H + NAD + (carrying from food) e- ATP 3 2 1

56. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 24.8 Electron Transport Chain Core Cyt c Q Intermembrane space Inner mitochondrial membrane Mitochondrial matrix H+H+ H+H+ Glycolysis Electron transport chain and oxidative phosphorylation Krebs cycle e- NADH + H + NAD + FAD (carrying from food) e- FADH 2 ATP 3 2 1

57. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 24.8 Electron Transport Chain Core Cyt c Q Intermembrane space Inner mitochondrial membrane Mitochondrial matrix H+H+ H+H+ H+H+ Glycolysis Electron transport chain and oxidative phosphorylation Krebs cycle e- NADH + H + NAD + FAD (carrying from food) e- FADH 2 e- ATP 3 2 1

58. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 24.8 Electron Transport ChainATP Synthase Core Cyt c Q Intermembrane space Inner mitochondrial membrane Mitochondrial matrix H+H+ H+H+ H+H+ H+H+ Glycolysis Electron transport chain and oxidative phosphorylation Krebs cycle e- NADH + H + NAD + FAD (carrying from food) e- FADH 2 e- ATP 3 2 1

59. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 24.8 Electron Transport ChainATP Synthase Core ADP + Cyt c Q Intermembrane space Inner mitochondrial membrane Mitochondrial matrix ATP PiPi H+H+ H+H+ H+H+ H+H+ H+H+ Glycolysis Electron transport chain and oxidative phosphorylation Krebs cycle e- NADH + H + NAD + FAD (carrying from food) e- FADH 2 e- ATP 3 2 1

60. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 24.8 Electron Transport ChainATP Synthase Core ADP + Cyt c Q Intermembrane space Inner mitochondrial membrane Mitochondrial matrix ATP PiPi H+H+ 2H+H+ + H+H+ H+H+ H+H+ H+H+ O2O2 H2OH2O Glycolysis Electron transport chain and oxidative phosphorylation Krebs cycle e- 1212 NADH + H + NAD + FAD (carrying from food) e- FADH 2 e- ATP 3 2 1

61. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Electronic Energy Gradient  The transfer of energy from NADH + H + and FADH 2 to oxygen releases large amounts of energy  This energy is released in a stepwise manner through the electron transport chain

62. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Electronic Energy Gradient  The electrochemical proton gradient across the inner membrane:  Creates a pH gradient  Generates a voltage gradient  These gradients cause H + to flow back into the matrix via ATP synthase PLAY Electron Transport

63. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Figure 24.9

64. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings ATP Synthase  The enzyme consists of three parts: a rotor, a knob, and a rod  Current created by H + causes the rotor and rod to rotate  This rotation activates catalytic sites in the knob where ADP and P i are combined to make ATP

65. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Structure of ATP Synthase Figure 24.10

66. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Summary of ATP Production Figure 24.11

67. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Glycogenesis and Glycogenolysis  Glycogenesis – formation of glycogen when glucose supplies exceed cellular need for ATP synthesis  Glycogenolysis – breakdown of glycogen in response to low blood glucose Figure 24.12

68. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Gluconeogenesis  The process of forming sugar from noncarbohydrate molecules  Takes place mainly in the liver  Protects the body, especially the brain, from the damaging effects of hypoglycemia by ensuring ATP synthesis can continue

69. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Lipid Metabolism  Most products of fat metabolism are transported in lymph as chylomicrons  Lipids in chylomicrons are hydrolyzed by plasma enzymes and absorbed by cells  Only neutral fats are routinely oxidized for energy

70. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Lipid Metabolism  Catabolism of fats involves two separate pathways  Glycerol pathway  Fatty acids pathway

71. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Lipid Metabolism  Glycerol is converted to glyceraldehyde phosphate  Glyceraldehyde is ultimately converted into acetyl CoA  Acetyl CoA enters the Krebs cycle

72. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Lipid Metabolism  Fatty acids undergo beta oxidation which produces:  Two-carbon acetic acid fragments, which enter the Krebs cycle  Reduced coenzymes, which enter the electron transport chain

73. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Lipid Metabolism Figure 24.13

74. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Lipogenesis and Lipolysis  Excess dietary glycerol and fatty acids undergo lipogenesis to form triglycerides  Glucose is easily converted into fat since acetyl CoA is:  An intermediate in glucose catabolism  The starting molecule for the synthesis of fatty acids

75. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Lipogenesis and Lipolysis  Lipolysis, the breakdown of stored fat, is essentially lipogenesis in reverse  Oxaloacetic acid is necessary for the complete oxidation of fat  Without it, acetyl CoA is converted into ketones (ketogenesis)

76. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Lipogenesis and Lipolysis Figure 24.14

77. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Lipid Metabolism: Synthesis of Structural Materials  Phospholipids are important components of myelin and cell membranes

78. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Lipid Metabolism: Synthesis of Structural Materials  The liver:  Synthesizes lipoproteins for transport of cholesterol and fats  Makes tissue factor, a clotting factor  Synthesizes cholesterol for acetyl CoA  Uses cholesterol to form bile salts  Certain endocrine organs use cholesterol to synthesize steroid hormones

79. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Protein Metabolism  Excess dietary protein results in amino acids being:  Oxidized for energy  Converted into fat for storage  Amino acids must be deaminated prior to oxidation for energy

80. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Protein Metabolism  Deaminated amino acids are converted into:  Pyruvic acid  One of the keto acid intermediates of the Krebs cycle  These events occur as transamination, oxidative deamination, and keto acid modification

81. Copyright © 2006 Pearson Education, Inc., publishing as Benjamin Cummings Amino Acid Oxidation Figure 24.15