Biochem 501 Lecture 24: Regulation of Blood Glucose II: Glycogen Metabolism

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Biochem 501 Lecture 24: Regulation of Blood Glucose II: Glycogen Metabolism
2013-10-30 21:40:56
Biochem 501

Biochem 501
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  1. How is excesses Glucose stored?
    As glycogen in animals/starch in plants
  2. Most common tissues for Glycogen synthesis/storage
    • Liver and Skeletal Muscle
    • Muscles use it in glycolysis for ATP
    • Liver breaks it down to glucose and sends it where it is needed
  3. How is Glycogen stored in blood stream?
    In glycogen granules, which also contain tools for making/breaking glycogen
  4. Structure of Glycogen
    • Glucose residues bound together in alpha-1,4-glycosidic bonds.
    • Branched points are alpha-1,6-glycosidic bonds
  5. Degradation of Glycogen
    Glucosen+1 + Pi --> Glucosen + G-1-P
  6. Glycogen Synthesis
    Glucosen + UDP-glucose --> Glucosen+1 + UDP
  7. Glycogen Phosphorylase
    Pops a glucose off with an added Pi on it
  8. Glycogen Transferase
    Moves chain from branches side chain to main chain
  9. alpha-1->6 Glycosidase
    Takes the branch bounded glucose and removes it
  10. Regulation of Glycogen Phosphorylase (a)
    • Glucagon signals phosphorylase b kinase to phosphorylate phosphorylase a making it more active
    •       -epinephrine, Ca2+, AMP all also raise it
    • Phosphorylase a phosphatase dephosphorylates making less active
  11. Glucose-6-Phosphatase
    • In liver/Kidney
    • Not in muscle/adipose
    • Needed to secrete glucose
    • Defines role for glycogen in liver/muscle
    • Used in Bypass step 3 of gluconeogenesis
  12. Where does Glucose-6-Phosphate turn G6P to Glucose and Pi
    ER Lumen, then ported out into blood via GLUT2
  13. 4 Stages of Glycogen Synthesis
    • -Conversion of G6P to G1P by phosphoglucomutase
    • -Glucose phosphate is converted to UDP-glucose by UDP-glucose pyrophosphorylase
    • -UDP-glucose adds itself to glucose chain in glycogen
    • -Make branches with glycosyl-4:6 transferase
  14. Activation of G-1-P for Glycogen synthesis
    G-1-P + UTP --> UDP-glucose + PPi
  15. Plant Starches
    • Amylose: Not branched
    • Amylopectin: Branched like glycogen, less frequent