Glycogen Metabolism

Question 1

What is the role of glucose in the liver vs. perepheral tissue?

Answer 1

In the liver, it serves as a buffer for the BGLs. In the periphery, it’s a buffer for Glucose-6-P within the cell (especially for muscle tissue.)

Question 2

Fasting hypoglycemia and muscle pain during exercise suggest what?

Answer 2

Defects in glycogen metabolism

Question 3

What does the first step of glycogen synthesis, phosphorylation, do to the glucose molecule?

Answer 3

It traps it in the cell and activates it.

Question 4

Glycogen synthase adds [ ] onto the [ ] end of the growing glycogen chain.

Answer 4

UDP-Glucose; 4 Carbon end

Question 5

What enzyme initiates a branch after about 11 glucose units on glycogen?

Answer 5

Branching enzyme (glycosyl 4 –> 6 transferase)

Question 6

What are some advantages of the branched glycogen structure?

Answer 6

Increases solubility
Has more active ends, so glycogenolysis and glycogenesis can happen rapidly
Doesn’t rely on activation of new genes.

Question 7

What is the first step to glycogen degradation?

Answer 7

Glycogen phosphorylase cleaves units of glucose from glycogen chains and adds inorganic phosphate to make glucose 1-phosphate.

Question 8

The fed state is usually associated with dephosphorylation (T/F)

Answer 8

T, insulin activates phosphatases that remove phosphates.