6. Glycogen metabolism

Question 1

2 major storage sites of Glycogen

Answer 1

Liver (10% by weight) Skeletal muscle (2% by weight)

Question 2

Glycogen Phosphorylase (GP)

Answer 2

Breakdown of glycogen

Question 3

Glycogen Synthase (GS)

Answer 3

Synthesis of Glycogen

Question 4

Phosphorylase Kinase (PK)

Answer 4

Activated by cAMP

↑ activity of GP

↓ activity of GS

Question 5

Protein Phosphatase-1 (PP1)

Answer 5

↓ PK

↓GP

↑ GS

Question 6

Liver

Answer 6

Stores glycogen after a carbohydrate meal

Makes free (blood) glucose

Question 7

Skeletal muscle

Answer 7

Synthesizes glycogen at rest

degrades it during exercise

Makes glucose for own use

Question 8

3 steps of Glycogen degradation

Answer 8

Glycogen → Glucose-1-phosphate by GP

Remodelling of glycogen for further degradation

Glucose-1-phosphate→ Glucose-6-phosphate by Phosphoglucomutase

Question 9

Control of Glycogenolysis in the muscle:

Answer 9

GP affected by allosteric factors

signal the energy state of the cell

Question 10

Control of Glycogenolysis in the liver/kidney

Answer 10

By reversible phosphorylation

which is responsive to hormones:

Epinephrine + Glucagon = stimulate glycogen breakdown

Question 11

Synthesis of Glycogen

Answer 11

formation of UDP-Glucose

UDP-Glucose is added to a growing chain of glycogen

Question 12

Control of Glycogen Degradation

Answer 12

PP1

“Switches off” GP

Question 13

3 factors that stimulate breakdown of glycogen

Answer 13

1) Glucagon
2) Epinephrine
3) Muscle contraction