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