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Citric Acid Cycle

Anabolism and Catabolism (Heterotrophs). Figure 17-1. Oxidative Fuel Metabolism. Summary of Anaerobic Glycolysis. Glucose 2 ADP 2 Pi. . 2 Lactate 2 ATP 2 H2O 2 H . Energetics of Fermentation. Glucose

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Citric Acid Cycle

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    1. Citric Acid Cycle

    2. Anabolism and Catabolism (Heterotrophs)

    3. Oxidative Fuel Metabolism

    4. Summary of Anaerobic Glycolysis

    5. Energetics of Fermentation

    6. Carbon Atom Oxidation

    7. Oxidation-Reduction Reactions

    8. Electron Transfer

    9. Electron Transport Oxidative Phosphorylation

    10. Oxidative Phosphorylation

    11. Citric Acid Cycle

    12. Amphibolic Nature of Citric Acid Cycle

    13. Summary of Citric Acid Cycle

    14. Synthesis of Acetyl-CoA

    15. Sources of Acetyl-CoA Carbohydrates (sugars via glycolysis) Fats (fatty acids) Proteins (amino acids)

    16. Oxidative Fuel Metabolism

    17. Pyruvate Dehydrogenase (PDH) Formation of Acetyl-SCoA Multienzyme Complex

    18. Pyruvate Dehydrogenase (Formation of Acetyl-SCoA)

    19. Pyruvate Dehydrogenase (Multienzyme Complex) E1: Pyruvate Dehydrogenase or Pyruvate Decarboxylase E2: Dihydrolipoyl Transacetylase E3: Dihydrolipoyl Dehydrogenase

    20. Multienzyme Complexes Enhanced reaction rates Channeling of reaction intermediates Coordinate regulation

    21. Electron Micrograph of E. coli Pyruvate Dehydrogenase

    22. Structural Organization of E. coli Pyruvate Dehydrogenase

    23. Pyruvate Dehydrogenase (Mammalian Enzyme) E1, E2, and E3 E3 binding protein Kinase (regulation) Phosphatase (regulation)

    24. Coenzymes and Prosthetic Groups of Pyruvate Dehydrogenase

    25. Thiamin Pyrophosphate

    26. Lipoic Acid

    27. Reduction of Lipoamide

    28. Coenzyme A

    29. NAD+

    30. Flavin Adenine Dinucleotide (FAD)

    31. Reduction of FAD

    32. Pyruvate Dehydrogenase (Formation of Acetyl-SCoA)

    33. Overall Reaction of Pyruvate Dehydrogenase

    34. Mechanism of Pyruvate Dehydrogenase (Decarboxylation of Pyruvate)

    35. Mechanism of Decarboxylation of Pyruvate

    36. Mechanism of Pyruvate Dehydrogenase (Hydroxyethyl Group Transfer)

    37. Mechanism of Hydroxyethyl Group Transfer

    38. Mechanism of Pyruvate Dehydrogenase (Transesterification)

    39. Mechanism of Transesterification

    40. Mechanism of Pyruvate Dehydrogenase (Reoxidation of Dihydrolipoamide)

    41. Mechanism of Pyruvate Dehydrogenase (Oxidation of E3–FADH2)

    42. Mechanism of Reoxidation of Dihydrolipoamide

    43. Mechanism of Oxidation of E3–FADH2

    44. A Swinging Arm Transfers Intermediates

    45. Pyruvate Dehydrogenase (Formation of Acetyl-SCoA)

    46. Regulation of Pyruvate Dehydrogenase Product Inhibition (competitive) NADH Acetyl-SCoA Phosphorylation/Dephosphorylation PDH Kinase: inactivation PDH Phosphatase: reactivation

    47. Regulation of PDH Kinase (Inactivation) Activators NADH Acetyl-SCoA Inhibitors Pyruvate ADP Ca2+ (high Mg2+) K+

    48. Regulation of PDH Phosphatase (Reactivation) Activators Mg2+ Ca2+

    49. Reactions of the Citric Acid Cycle

    50. Enzymes of the Citric Acid Cycle Citrate Synthase Aconitase Isocitrate Dehydrogenase ?-Ketoglutarate Dehydrogenase Succinyl-CoA Synthetase Succinate Dehydrogenase Fumarase Malate Dehydrogenase

    51. Citrate Synthase (citrate condensing enzyme)

    52. Mechanism of Citrate Synthase (Formation of Acetyl-SCoA Enolate)

    53. Mechanism of Citrate Synthase (Acetyl-CoA Attack on Oxaloacetate)

    54. Mechanism of Citrate Synthase (Hydrolysis of Citryl-SCoA)

    55. Regulation of Citrate Synthase Pacemaker Enzyme (rate-limiting step) Rate depends on availability of substrates Acetyl-SCoA Oxaloacetate

    56. Aconitase

    57. Iron-Sulfur Complex (4Fe-4S]

    58. Stereospecificity of Aconitase Reaction

    59. Stereospecificity in Substrate Binding

    60. NAD+–Dependent Isocitrate Dehydrogenase

    61. Mechanism of Isocitrate Dehydrogenase (Oxidation of Isocitrate)

    62. Mechanism of Isocitrate Dehydrogenase (Decarboxylation of Oxalosuccinate)

    63. Mechanism of Isocitrate Dehydrogenase (Formation of ?-Ketoglutarate)

    64. Regulation of Isocitrate Dehydrogenase Pulls aconitase reaction Regulation (allosteric enzyme) Positive Effector: ADP (energy charge) Negative Effector: ATP (energy charge) Accumulation of Citrate: inhibits Phosphofructokinase

    65. Aconitase

    66. ?-Ketoglutarate Dehydrogenase

    67. a-Ketoglutarate Dehydrogenase (Multienzyme Complex) E1: ?-Ketoglutarate Dehydrogenase or ?-Ketoglutarate Decarboxylase E2: Dihydrolipoyl Transsuccinylase E3: Dihydrolipoyl Dehydrogenase (same as E3 in PDH)

    68. Regulation of ?-Ketoglutarate Dehydrogenase Inhibitors NADH Succinyl-SCoA Activator: Ca2+

    69. Origin of C-atoms in CO2

    70. Succinyl-CoA Synthetase (Succinyl Thiokinase)

    71. Citrate Synthase (citrate condensing enzyme)

    72. Thermodynamics (Succinyl-SCoA Synthetase)

    73. Evidence for Phosphoryl-enzyme Intermediate (Isotope Exchange)

    74. Mechanism of Succinyl-CoA Synthetase (Formation of High Energy Succinyl-P)

    75. Mechanism of Succinyl-CoA Synthetase (Formation of Phosphoryl-Histidine)

    76. Mechanism of Succinyl-CoA Synthetase (Phosphoryl Group Transfer)

    77. Nucleoside Diphosphate Kinase (Phosphoryl Group Transfer)

    78. Succinate Dehydrogenase

    79. Malonate Inhibitor of Succinate Dehydrogenase

    80. Covalent Attachment of FAD

    81. Fumarase

    82. Mechanism of Fumarase

    83. Malate Dehydrogenase

    84. Thermodynamics

    85. Citric Acid Cycle

    86. Amphibolic Nature of Citric Acid Cycle

    87. Glycolysis and Gluconeogenesis

    88. Substrate Cycles in Glucose Metabolism

    89. Reversal of Pyruvate Kinase Reaction

    90. Fatty Acid Biosynthesis Condensation of 2-C Units Reversal of b-Oxidation

    91. Pathway Overview

    92. Comparison (Fatty Acid Biosynthesis versus Degradation) Different pathway Different location Uses ACP versus CoASH D-hydroxyacyl group versus L-hydroxyacyl group Uses NADPH versus NAD+ and FAD Uses Malonyl-CoA versus Acetyl-CoA

    93. Transport of Mitochondrial Acetyl-CoA into the Cytosol

    94. Ammonium Assimilation (Biosynthetic Glutamate Dehydrogenase)

    95. Ammonium Assimilation (Glutamine Synthetase)

    96. Microbial Nitrogen Acquisition (Metabolic Sources of Organic Nitrogen) Glutamate (90%) Amino Acids (90%) Purines (50%) Pyrimidines (50%) Glutamine (10%) Amino Acids Amino Sugars NAD+ PABA Purines (50%) Pyrimidines (50%)

    97. Role of Glutamate (Nitrogen Donor)

    98. Role of Glutamine (Nitrogen Donor)

    99. Aspartate and Asparagine Biosynthesis

    100. Glutamate and Glutamine Biosynthesis

    101. Proline Biosynthesis

    102. Arginine Metabolism in Microorganisms (Linear Biosynthetic Pathway)

    103. Generation of Citric Acid Cycle Intermediates

    104. Pyruvate Carboxylase Mitochondrial Matrix

    105. Pyruvate Carboxylase

    106. Biotin Cofactor (CO2 Carrier)

    107. Reaction Mechanism I (Dehydration/Activation of HCO3–)

    108. Reaction Mechanism II (Transfer of CO2 to Pyruvate)

    109. Fates of Oxaloacetate

    110. Regulation of Pyruvate Carboxylase Allosteric Activator Acetyl-SCoA

    111. Glyoxylate Cycle Glyoxysome Plants and Some Microorganisms

    112. Citrate Synthase (citrate condensing enzyme)

    113. Aconitase

    114. Glyoxylate Cycle Enzymes (Glyoxysome)

    115. Malate Dehydrogenase

    116. Net Reaction of Glyoxylate Cycle

    117. Glyoxylate Cycle and the Glyoxysome

    118. Regulation of the Citric Acid Cycle

    119. Amphibolic Nature of TCA Cycle

    120. Products of the Citric Acid Cycle

    121. ATP Production

    122. Regulatory Mechanisms Availability of substrates Acetyl-CoA Oxaloacetate Oxygen (O2) Need for citric acid cycle intermediates as biosynthetic precursors Demand for ATP

    123. Free Energy Changes of Citric Acid Cycle Enzymes

    124. Regulation of Pyruvate Dehydrogenase Product Inhibition (competitive) NADH Acetyl-SCoA Phosphorylation/Dephosphorylation PDH Kinase: inactivation PDH Phosphatase: reactivation

    125. Covalent Modification and Regulation of PDH

    126. Regulation of PDH Kinase (Inactivation) Activators NADH Acetyl-SCoA Inhibitors Pyruvate ADP Ca2+ (high Mg2+) K+

    127. Regulation of PDH Phosphatase (Reactivation) Activators Mg2+ Ca2+

    128. Regulation of Citrate Synthase Pacemaker Enzyme (rate-limiting step) Rate depends on availability of substrates Acetyl-SCoA Oxaloacetate

    129. Regulation of Isocitrate Dehydrogenase Pulls aconitase reaction Regulation (allosteric enzyme) Positive Effector: ADP (energy charge) Negative Effector: ATP (energy charge) Accumulation of Citrate: inhibits Phosphofructokinase

    130. Regulation of ?-Ketoglutarate Dehydrogenase Inhibitors NADH Succinyl-SCoA Activator: Ca2+

    131. Regulation of the Citric Acid Cycle

    132. Regulation of Central Metabolic Pathways

    133. Metabolism During Exercise

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