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Chapter 23 Gluconeogenesis, Glycogen Metabolism, and the Pentose Phosphate Pathway

Chapter 23 Gluconeogenesis, Glycogen Metabolism, and the Pentose Phosphate Pathway. 23.1 Gluconeogenesis. 23.1.1 Overview. 23.1.2 Gluconeogenesis Is Not Merely the Reverse of Glycolysis. 1. Pyruvate carboxylase. 2. Transport of oxaloacetate out of the michondrion.

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Chapter 23 Gluconeogenesis, Glycogen Metabolism, and the Pentose Phosphate Pathway

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  1. Chapter 23 Gluconeogenesis, Glycogen Metabolism, and the Pentose Phosphate Pathway

  2. 23.1 Gluconeogenesis 23.1.1 Overview 23.1.2 Gluconeogenesis Is Not Merely the Reverse of Glycolysis

  3. 1. Pyruvate carboxylase

  4. 2. Transport of oxaloacetate out of the michondrion Pyruvate carboxylase Malate dehydrogenase Malate dehydrogenase

  5. 3. PEP Carboxykinase

  6. 4. Fructose-1,6-Bisphosphatase

  7. 5. Glucose-6-Phosphatase

  8. 23.1.3 Energy Used Pyruvate carboxylase 1ATP * 2 = 2ATP PEP carboxykinase 1GTP * 2 = 2GTP Phosphoglycerate kinase 1ATP * 2 = 2ATP TOTAL = 6ATP

  9. 23.1.4 Precursors for gluconeogenesis Glycerol Lactate Pyruvate Citric acid cycle intermidiates The carbon skeletons of the amino acid

  10. The cori cycle

  11. 23.1.4 Reciprocal Regulation of Glycolysis and Gluconeogenesis

  12. 23.2 Glycogen Metabolism 23.2.1 Glycogen Catabolism • Glycogen phosphorylase • Glycogen-debranching enzyme

  13. glycogen + Pi glycogen + G-1-P (n residues) (n-1 residues) phosphoglucomutase G-1-P G-6-P

  14. 23.2.2 Glycogen Synthesis • UDP-glucose pyrophosphorylase • glycogen synthase • branching enzyme • [amylo-(1-4 1-6) transglycosylase]

  15. 23.2.3 Control of Glycogen Metabolism • Allosteric control and covalent modification Phosphorylase kinase ATP ADP Phosphorylase b phosphorylase a (dephosphorylated , (phosphorylated, inactive) active) Pi Protein phosphatase I

  16. Protein phosphatase Pi Glycogen synthase b Glycogen synthase a (phosphorylated , (dephosphorylated, inactive) active) ADP ATP Protein kinase A

  17. Hormones Regulate Glycogen Synthesis and Degradation Insulin

  18. Glucagon Epinephrine

  19. Cortisol

  20. 23.3 The Pentose Phosphate Pathway 23.3.1 Overview Hexosephosphate shunt Hexose monophosphate shunt Phosphogluconate pathway 23.3.2 Main Reaction of the Pathway

  21. 1. The oxidative steps of the pentose phosphate pathway Glucose-6-phosphate dehydrogenase Gluconolactonase 6-Phosphogluconate dehydrogenase

  22. 2. The nonoxidative steps of the pentose phosphate pathway Phosphopentose isomerase Phosphopentose epimerase Transketolase Transaldolase

  23. Phosphopentose isomerase

  24. Transaldolase

  25. 23.3.3 Utilization of G-6-P Depends on the Cell’s Needs for ATP, NADPH, and Ribose-5-P

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