Glycogen

Question 1

Glycogenolysis regulatory enzymes?

Answer 1

• Glycogen Phosphorylase: specific break down of alpha(1->4) bonds; rate-limiting step
• Debranching Enzymes: Breaks alpha(1->6) bonds; tranglycosylase & glucosidase activities

Question 2

Compare and contrast Hormones of glycogen degradation in the liver and muscle with reference to

Answer 2

• Liver: Glucagon stimulates glycogenolysis

- Muscle: Ca2+ & epinepherine stimulate glycogenolysis

Question 3

Glycogenic regulatory enzymes?

Answer 3

• Glycogen synthase

- Branching Enzyme

Question 4

Regulation of Liver glycogenesis and glycogen breakdown?

Answer 4

• Glycogenesis: Insulin favours glycogenesis; Glycogen synthase-P is dephosphorylated by Phosphatase to become Activated
• Glycogenolysis:
  (1) Glucagon -> AC -> cAMP -> PKA -> Phosphorylase Kinase -> Hepatic Glycogen Phosphorylase-a is activated
  (2) Epinepherine -> alpha-AR -> PLC -> IP3 -> Ca2+ release from SR -> Calmodulin activation -> activates Hepatic Glycogen Phosphorylase

Question 5

Regulation of Muscle glycogenesis and glycogen breakdown?

Answer 5

• Glycogenesis: Insulin favours glycogenesis; Glycogen synthase is phosphorylated by phosphorylated to become Activated
• Glycogenolysis: Phosphorylase Kinase activated via 2 signaling pathways in muscles:
  (1) Ca2+ activates Calmodulin complex or
  (2) β-AR stimulation;
  Activated Phosphorylase Kinase will activate Glycogen Phosphorylase-a & promote glycogen breakdown.