07 Glycogen

  • muscles cannot release glucose from glycogen

  • 1-4 linear linkage

  • 1-6 branching

  • branching makes it more soluble and better storage

  • UDP: uridine

  • lysosomes can collect glycogen and break it down to glucose

  • glycogen phosphorylase shrink purple link down to 3 or so

  • debranching enzyme moves purple to red, releasing one molecule of glucose (green)

  • glucagon/E phosphorylates both enzymes both have opposite effects

  • glycogen phosphorylase activity increases

  • glycogen synthase activity decreases

  • insulin results in dephosphorylation of both and opposite effects

  • activate glycogen phosphorylase in absence of hormones

  • immediate activation instead of hormonal

Glycogen Storage Diseases

  • liver defective enzyme: hypoglycemia

  • enzyme defective in muscle: weakness

Von Gierke

  • can't release glucose between meals

  • can't get glucose out of liver = hepatomegaly

  • muscles will be ok

  • no symptoms of muscle weakness

  • consume corn starch between meals

Pompe

  • liver is ok, continue make glucose

  • no hypoglycemia symptoms

  • entrapment of glycogen inside muscle cells

  • enlarged tongue classic finding

Cori

  • gluconeogenesis intact from other sources: hypoglycemia not as severe

  • no glucose in muscles either: weakness

  • usually no seizures

  • muscle symptoms distinguish from Von Gierke

McArdle

  • no liver problems, no hypoglycemis

  • muscle difficulties

  • can get muscle damage with exercise

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