W Interorgan Pathways - Interorgan Metabolic Pathways...

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Interorgan Metabolic Pathways • The alanine cycle • The Cori cycle • Glucose transporters • Fuel reserves in organism • Starvation and obesity Learning Objectives
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The Cori Cycle • High oxygen consumption continuous tens minutes after vigorous muscle activity is over. • Lactate produced in the muscle is transported via bloodstream to the liver where it is converted to pyruvate by lactate dehydrogenase. Fig. 22-6
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The Cori Cycle • Gluconeogenesis in the liver regenerates glucose from lactate. The process requires ATP, which is produced by the oxidative phosphorylation with consumption of O 2 . • If glucose were synthesized by the muscle, the demand of the working muscle for ATP would increase dramatically. • During prolonged physical activity, the liver helps muscle to do the job by taking up lactate and returning glucose.
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The Glucose-Alanine Cycle • Glycolysis in muscle yields pyruvate that serves as the acceptor of amino group in reactions catalyzed by certain aminotransferases. R-CH(NH 3 + )-COO - + H 3 C-C(O)-COO - R-C(O)-COO - + H 3 C-CH(NH 3 + )-COO - Amino acid Pyruvate -Keto acid Alanine • Alanine is released to the bloodstream and transported to the liver. • In the liver, alanine is converted to pyruvate, which is used for gluconeogenesis. Fig. 22-7
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The Glucose-Alanine Cycle • Glucose produced from pyruvate is returned to muscle. • The amino groups transported to the liver with alanine are transformed to urea. • During the workload,
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This note was uploaded on 04/10/2011 for the course SCIENCE 2EE3 taught by Professor Zhorov during the Spring '11 term at McMaster University.

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W Interorgan Pathways - Interorgan Metabolic Pathways...

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