Glycogen Synthesis And Regulation Flashcards
What controls liver mediated control of blood glucose?
Insulin and glycogen
Compare hexokinase and glucokinase
Hexokinase is more general, can metabolise glucose at a lower conc as it has a lower km, whereas glucokinase is more specific to glucose - found in liver it has a higher km so only works when glucose conc is high
What enzymes cause branching in the structure of glycogen
Branching enzymes
What enzyme causes the extension of straight chains in glycogen?
Glycogen synthase
What enzyme removes terminal glucose molecules from glycogen?
Glycogen phosphorylase using a Pi
What enzymes remove stumps remaining after branches are hydrolysed in glycogen?
Debranching enzymes
How is glucose within a cell after being removed from glycogen, moved into blood stream?
Glucose will be in the form glucose-1-p
And this is converted into glucose-6-p by a mutate enzyme, which cannot cross membranes so is trapped in the hepatocytes.
Then glucose-6-phosphatase (only found in the liver) converts it into glucose which can cross membranes and enter the bloodstream
Where is glucose-6-phosphatase found?
In the liver only
What’s the active version of glycogen synthase?
Glycogen synthase a, unphosphorylated
What’s the active form of glycogen phosphorylase?
Glycogen phosphorylase b, phosphorylated
How does AMP affect glycogen metabolism?
It’s an allosteric activator of glycogen phosphorylase, increasing glycogen metabolism
How does ATP affect glycogen metabolism?
It’s an allosteric inhibitor of glycogen phosphorylase, decreasing glycogen metabolism
What is Von Gierkes disease?
Defective glucose-6-phosphatase,
Enlarged liver and hypoglycaemia
What is Pompes disease?
Lysosomal glycosidase defective, muscle weakness, cardiac failure
What is McArdles disease?
Glycogen phosphorylase defective, exercise intolerance
