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Lecture33-2007 - Regulation depends on the purpose of a...

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1 Regulation of Carbohydrate Metabolism Lecture 33 Chapters 14-4, 15-4C Regulation depends on the purpose of a pathway Pathways for synthesis and degradation are separate, allowing reciprocal regulation: – Glycolysis/Gluconeogenesis Glycogen breakdown/Glycogen synthesis Purpose of carbohydrate metabolism is different depending on cell type. Carbohydrate metabolism in muscle • Goal: – Metabolize glucose for own energy needs. – Store glucose for own needs. Regulation based on Energy State of individual cells Energy State of Cell High energy state has high ratios of: ATP/ADP + AMP – NADH/NAD+ – Acetyl-CoA/CoA High energy state activates glycogen synthesis. Low energy state activates glycogen breakdown.
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2 Regulation in Muscle. Breaks down glycogen for rapid bursts of energy - ATP, G6P + AMP, Epinephrine - Epinephrine Epinephrine (adrenaline): “Fight or Flight” hormone. Catecholamine (derived from Tyr). Made in adrenal cortex. Leads to production of cAMP. Levels of cAMP controlled by relative activities of adenylate cyclase and cAMP phosphodiesterase: + Epinephrine Protein Kinase A Also called cAMP-dependent protein kinase. Heterotetramer: 2 Regulatory subunits (R) bind cAMP 2 Catalytic subunits (C) phosphorylate target proteins Activated by cAMP: R 2 C 2 + 4 cAMP <=> 2 C + R 2 (cAMP) 4 (inactive) (active)
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3 Epinephrine cAMP Glycogen Breakdown Muscle Kinase cascade. Amplification at each step: 1 PKA 10 Phos. Kinase 100 Phosphorylase 1000 Glc released (liver) Allosteric modulators work together with phosphorylation to regulate phosphorylase activity Epinephrine (active) (active) (inactive) (inactive) Muscle Insulin activates PPase-1 and reduces cAMP Regulation of Glycolysis/Gluconeogenesis in Muscle Purpose of pathways: – For energy needs of muscle.
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