Glycogen metabolism

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  • Created by: jessica
  • Created on: 12-12-12 10:11
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  • Glycogen metabolism
    • Synthesis needs Uridine Diphosphate Glucose (UDP-glucose)
      • UDP-glucose made by reaction of UTP and glucose-1-phosphate
        • Irreversible hydrolysis of pyrophosphate drives UDP-glucose synthesis
          • Glucose-1-phosphate + UTP = UDP-glucose + PPi (reversible reaction) PPi + H2O=2Pi
          • Glucose-1-phosphate + UTP+ H2O=UDP-glucose + 2Pi
      • Glycogenin is the primer for glycogen synthesis
    • Glucose residues linked by 1-4 glycosidic bonds
      • Every 10 residues, branches by 1-6 glycosidic bonds
    • Glucose-6-phosphate from glycogen has 3 fates
      • 3:processed by pentose phosphate pathway to yield NADPH and ribose derivatives
      • 1:initial substrate for glycolysis
      • 2:converted into free glucose for release into bloodstream
    • Glycogen molecule has 12 layers of glucose molecules
    • Synthesis equation
      • Glycogen(n) + UDP-glucose = Glycogen(n) + 1 + UDP
    • Degradation has 3 steps
      • 2:remodelling glycogen substrate for more degradation
        • Transferase and alpha 1-6 glucosidase remodel
      • 1:release of glucose-1-phosphate from glycogen
        • Glycogen (n residues) + Pi = Glucose-1-phosphate + Glycogen (n-1 residue) (reversible reaction)
          • Orthophosphate splits linkage between C1 of terminal residue and C4 of adjacent residue
          • Phosphogluco-mutase converts glucose-1-phosphate to glucose-6-phosphate
      • 3:conversion of glucose-1-phosphate into glucose-6-phosphate for further metabolism
    • Degradation Equation
      • Glycogen(n) + 1+Pi=Glycogen(n) + Glucose-1-phosphate
    • Branching
      • increases solubility and synthesis/ degradation rate
    • insulin stimulates synthesis
      • inactivates glycogen synthase and activates protein kinases

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