Chapter 14 notes - Carbohydrate Metabolism I Glycolysis,...

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Unformatted text preview: Carbohydrate Metabolism I Glycolysis, Gluconeogenesis, and the Pentose Phosphate Pathway Glucose Utilization in Animals 2 MCDB310 Chapter 14: Carbohydrate Metabolism H. & E. Buchner (1897): Cell-free yeast extract can convert sucrose into ethanol Glycolysis: Metabolic breakdown of glucose (C 6 ) into 2 molecules of pyruvate (C 3 ) to generate energy Present in all organisms and tissues; localized in cytoplasm Fermentation: Anaerobic breakdown of glucose Glycolysis: Overview 3 MCDB310 Chapter 14: Carbohydrate Metabolism C 6 H 12 O 6 glucose glycolysis ATP ethanol/lactic acid f e r m e n t a t i o n CO 2 + H 2 O The First Stage of Glycolysis - Preparation 4 MCDB310 Chapter 14: Carbohydrate Metabolism Phosphorylated compounds cannot cross membranes spontaneously Phosphorylation reactions (1, 3) are irreversible ( G << 0) (1) Phosphorylation of Glucose MCDB310 Chapter 14: Carbohydrate Metabolism 5 Hexokinase can also phosphorylate other hexoses Induced fit mechanism prevents unwanted ATP hydrolysis (2) Glucose 6P Fructose 6P MCDB310 Chapter 14: Carbohydrate Metabolism 6 Converts the aldose glucose into the ketose fructose Ketose required for subsequent cleavage of C 6 2 C 3 (3) Phosphorylation of Fructose 6P MCDB310 Chapter 14: Carbohydrate Metabolism 7 Committed step in glycolysis: Targets sugar for break-down PFK-1 is highly regulated Introduces second phosphate both products of subsequent cleavage are phosphorylated (4) Cleavage of Fructose 1,6bisP MCDB310 Chapter 14: Carbohydrate Metabolism 8 Cleavage of Frc 1,6bisP is highly unfavorable under standard conditions ( G >> 0), but only slightly under physiological conditions ( G 1.3 kJ/mol) Mechanism of Aldolase (Class I) MCDB310 Chapter 14: Carbohydrate Metabolism 9 (5) Interconversion of Triose Phosphates MCDB310 Chapter 14: Carbohydrate Metabolism 10 Extremely fast reaction (k cat /K M of TIM: 210 8 M-1 s-1 ) Only glyceraldehyde 3P is used in further reactions The Second Stage of Glycolysis Pay Off 11 MCDB310 Chapter 14: Carbohydrate Metabolism Includes 2 steps (7, 10) that generate ATP Step 6 generates NADH (oxidation) NAD + must be recovered to keep glycolysis going ( oxidative phosphorylation, fermentation) All steps except (10) are reversible (6) Oxidation of Glyceraldehyde 3P...
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Chapter 14 notes - Carbohydrate Metabolism I Glycolysis,...

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