Glycogen Metabolism

Question 1

Major concentrations are found in what part of the body?

Glycogen (2)

Answer 1

1. Skeletal muscle
2. Liver

Question 2

What does liver glycogen do?

Answer 2

Helps maintain adequate blood glucose concentration-serves as a buffer for the overall blood glucose level

Question 3

What does glycogen do in muscle?

Answer 3

ENERGY
Strenuous exercise/fight or flight response

Question 4

What is a faster energy source fat or glycogen?

Answer 4

GLYCOGEN

Fat can’t be oxidized to produce energy in the absence of O2

Question 5

What is the purpose of glycogen branching?

Answer 5

1. Speeds synthesis and degradation
2. Increases solubility of glycogen

Question 6

What are the two primers for Glycogen Synthesis?

Answer 6

1. Pre-existing glycogen
2. Glycogenin

Question 7

What is the high energy compounds that donate glycosyl units to the GROWING glycogen chain?

Answer 7

UDP-glucose

Question 8

What is the rate limiting step in glycogen synthesis?

Answer 8

Glycogen Synthase Mechanism

This is the elongation of branches in glycogen synthesis

Question 9

What makes the branches in glycogen?

Answer 9

Glycogen branching enzyme

4,6 transferase

Question 10

What are the 3 enzymes involved in glycogen breakdown?

Answer 10

1. Glycogen phosphorylase
2. Glucosyl alpha 4-4 transferase
3. Amylo alpha 1,6 glucosidase

Question 11

What enzyme releases free glucose?

Answer 11

Amylo alpha 1,6 glucosidase

Question 12

After glycogen phosphorylase cleaves alpha 1,4 glycosidic bonds at the non reducing end, what is the resulting structure called?

Answer 12

Limit dextrin

Question 13

What is the rate limiting step in glycogenolysis?

Answer 13

Glycogen Phosphorylase Reaction (shortening of the chains)

Question 14

What is the enzyme that is in the liver that is not in muscle?

This enzyme releases free glucose

Answer 14

Glucose 6-phosphatase

Question 15

Regulation of Glycogen Metabolism (4)

Answer 15

1. Glycogen synthase regulation (opposes that of glycogen phosphorylase
2. Allosteric control of glycogen synthase and glycogen phosphorylase
3. Hormonal control
4. Receptor mediated control

Question 16

Type II: Pompe Disease

Answer 16

• Lysosomal alpha (1,4)-glucosidase deficiency
• excessive glycogen concentrations found in vacuoles in lysosomes
• Early death
• Normal glycogen structure

Question 17

Type V: McArdle Syndrome

Answer 17

• Skeletal Muscle Glycogen Phosphorylase deficiency
• Temporary cramping/weakness after exercise
• Relatively benign

Question 18

Type VI: Hers Disease

Answer 18

• Liver Glycogen Phosphorylase Deficiency
• High glycogen content in liver
• mild fasting hypoglycemia
• Generally resolves by puberty

Question 19

Type Ia: Von Gierke Disease

Answer 19

• Glucose 6-Phosphatase Deficiency
• Fasting hypoglycemia:severe
• Affects liver AND kidney

Question 20

Type 2b: Von Gierke Disease

Answer 20

• Glucose 6-Phosphate Translocase deficiency