Brenda - Glycogen Synthesis

Question 1

List the molecules in glycogen synthesis
(5)

Answer 1

Glucose

Glucose-6-phosphate

Glucose-1-phosphate

UDP-Glucose

Glycogen

Question 2

List the enzymes of glycogen synthesi

Answer 2

Hexokinase

Phosphoglucomutase

UDP-glucose pyrophosphorylase

Glycogen synthase

Amylo(1-4 -1-6) transglycolysase

Question 3

What does glycogen synthase do?

Answer 3

Catalyses the addition of alpha-1-4 linkasges

Needs a primer (glycogenin)

Question 4

What does amylo-(1-4 - 1-6) transglycolyase do?

Answer 4

Breaks the alpha-1,4 link and forms an alpha-1,6 link

Creates branches which increases the solubility of glycogen

Question 5

What are the two forms of glycogen synthase

Answer 5

Active non phosphorylated a form

Inactive phosphorylated b form

Question 6

What activates glycogen synthase a?

Answer 6

Insulin

Question 7

How does insulin affect glycogen synthase a

Answer 7

a is the non phosphorylated form

Phosphorylation inactivates the enzyme

This is phosphorylated by GSK3

Insulin blocks GSk3

Question 8

How does insulin affect glycogen synthase b

Answer 8

b is the phosphorylated inactive form

Insulin activates PP1

PP1 dephosphorylates b

b is converted into the more active a form

Question 9

How does glucagon affect glycogen synthase

Answer 9

Glucagon blocks activation of glycogen synthase

Question 10

In general what affect does insulin have on glycogen synthesis?

Answer 10

Insulin promotes activation of glycogen synthase and also blocks it’s inhibition

Insulin stimulates synthesis of hexokinase

=> insulin stimulates glycogen synthesis

Question 11

List the hereditary glycogen storage diseases
(8)

Answer 11

Von Gierkes disease 1a
Von Gierkes disease 1b
Pompes disease
Cori’s disease
Andersens disease
McArdles
Her’s disease
Type O: Liver Glycogen Synthase Deficiency

Question 12

Write a note on Cori’s disease
(3)

Answer 12

Glycogen storage disease type III

Autosomal recessive metabolic disorder & inborn error of metabolism characterized by a deficiency in debranching enzyme.

Treatment: frequent feedings, high protein
diet

Question 13

Write a note on Andersens disease

Answer 13

Branching enz deficient

Very severe disease.

Patients rarely survive more than 4y.

Liver dysfunction.

Liver glycogen present in normal amounts
but contains long unbranched chains greatly
reduce solubility

Question 14

Write a note on McArdles
(4)

Answer 14

Muscle phosphorylase deficiency

Painful muscle cramps on exertion

Usually do not appear until early adulthood

Prevented by avoiding strenuous exercise