Lecture #70

  1. what is glycogen
    • homo-polymer of glucose
    • rapidly mobilized storage form of glucose
  2. function of glycogen
    maintain glucose homeostasis
  3. glucose is imp because
    • main energy source:brain and RBC
    • modify lips 
    • for PPP
  4. where do we get glucose
    • meals
    • glycogen and fasting 
    • GNG during prolonged fasting
  5. what is the locatioin of the glucogen?
    • in the cytosol  in cytosolic granuels 
    • liver
    • skeletal muscle
    • kidney
  6. what is the structure of glycogen
    • glycogen has many branches
    • a-1,4 linkages 9 main chain) with a-1,6 at the branching sites
  7. what does alpha-1,4 linkage mean?
    • the hydroxy on the anomeric is linked to the C4
    • a carbon is point downward alpha  mean that the carbon is point downwards
  8. what is the nonreducing end
    • without the aldhyde group 
    • this is where glucoses are added and removed
  9. what is the reducing end
    the end of the glycogen with the aldehyde
  10. what are the steps in glycogen synthesis ?
    Glucose>G6P9 ( via hexokinase or glucokinase ) >G1P ( via phosphoglucomustase)>UDPG (via UDG-glucose pyrophosphorylase ) >glycogen ( via transferase, synthase  and glycogen primer)
  11. what are the steps in glycogen degradation ?
    Glycogen> Glucose ( via glycogen phosphorylase + debranching enzyme)> G1P > G6P ( via phosphoglucomutase) >Glucose ( G6Phosphatase)
  12. synthesis of glycogen
  13. what does UTP do to glucose?
    it activates it so that it can link to other glucose  to make glycogen
  14. steps of glycogenesis
    Glucose 6 phosphate > G1P(via phosphoglucomutase)>UDP glucose ( via UDP glucose pyrophosphorylase)> Glycogen  (via glycogen synthase)
  15. what is necessary for glycogen synthase to wokr?
    • oligosaccharide primer
    • glycogenin
  16. how do the primers of  Glycogen synthesis  form ?
    through glucose autoglycosylation activity a tyrosine residue is added.
  17. what is glycogenin
    enzyme and scaffold, extending the carbohydrate chain up to 8 glucose oligomer using UDP-glucose donor
  18. how does the branching enzyme work for elongation ?
    it removes a 6 to 8 oligomer from non reducing end and attached it by a-1,6 linakage ( at least 4 residues from a branch point )
  19. why go glycogen branch?
    • more soluble 
    • creates a large # of non-reducing ends which increases the rate or synthesis and degradation
  20. function og glycogen synthase
    transfer glucose from UDP glucose to the non reducing end
  21. Break down of glycogen
  22. difference btw liver and muscle
    liver can push out glucose but muscles cannot.
  23. lysosomal degradation
    1-3% of glycogen is continuosly degraded by the lysosomal enzyme a-1,4 glucosidase
  24. Pompe disease
    • Type II glycogen storage disease
    • deficiency of the lysosomal alpha- 1,4glucosidase 
    • causing the build up of glycogen and impariment of normal functioning of organ especially heart
  25. epinephrine  and Glucagen both do what to glycogen
    trigger glycogen breakdown
  26. generally speaking insulin activates
  27. generally speaking glycogenand epinephrine activates
  28. Von Gierke Disease Type Ia and I1
    glucose cannot be released in the blood  and accumulates in liver and kidney
  29. what is the difference between Von Gierke Disease Type Ia and Ib
    • type Ia  is deficiency in Glucose 6 phosphatase 
    • Type Ib is deficency in glucose 6 phosphate translocase
  30. Cori disease
    the deb ranching enzyme is defective
  31. what is the process of changing fructose into glucose
    fructokinase and aldolase B triose kinase  which results in glyceraldehyde 3 phosphate.
  32. what is fructosuria
    fructose kinase deficency
  33. Hereidtary fructose intolerance ( HFI)
    aldolas B deficency resuling in decrease in cellular interstital phosphate and ATP
  34. what is sorbitol
    an alcohol form of glucose
  35. what is the glycogen phospgorylase
    this phosporylates the phosphorylase kinase
  36. what enzyme converts glucose to sorbital
    aldose reductase
Card Set
Lecture #70
Biochem Glycogen Metabolism