Bio 9 - Glycogen

Question 1

What does Branching enzyme convert?

Answer 1

Converts Uridine disphosphoglucose (UDP-glucose) into alpha-1,6 glycosidic linkages.

Question 2

What are the two forms of glycogen chain linkages?

Answer 2

Alpha-1,4 glycosidic linkages. Alpha-1,6 glycosidic linkages.

Question 3

Why can’t muscles perform gluconeogenesis?

Answer 3

Because it lacks glucose-6-phosphatase.

Question 4

Which enzyme breaks down alpha-1,4 glycosidic linkage to glucose-1-P?

Answer 4

Glycogen Phosphorylase.

Question 5

Which enzyme converts glucose-1-P to glucose-6-P?

Answer 5

Phosphoglucomutase.

Question 6

Which enzyme converts alpha -1,6 glycosidic linkage directly to glucose?

Answer 6

Alpha 1,6- glucosidase. AKA debranching enzyme.

Question 7

What does insulin does in terms of glycogen regulation?

Answer 7

It inhibits glycogen phosphorylase, stimulates glycogen synthase.

Question 8

What does High-stress state do in glycogen regulation?

Answer 8

Release epinephrine: beta-adrenergic receptors stimulate adenylyl cyclase, activating glycogen phosphorylase, stimulating glycogenolysis. Release glucagon: stimulates adenylyl cyclase, activating cAMP, which activates protein kinase A, activating glycogen phosphorylase kinase, activating glycogen phosphorylase: stimulating glycogenolysis.

Question 9

What is pathophysiology of McArdle disease?

Answer 9

AKA glycogen storage disease type V, it is due to the defect of the enzyme glycogen phosphorylase. This leads to accumulation of excess glycogen in the muscle, leading to edema from the osmotic pressure, leading to lysis of muscle cells, causing rhabdomyolysis (excess myoglobin in the serum), causing myoglobinuria, and renal failure. Can also cause muscle cramping but have normal life expectancy.

Question 10

What is pathophysiology of von Gierke disease?

Answer 10

AKA glycogen storage disease type I, caused by a defect in the enzyme glucose-6-phosphatase. Causes severe fasting hypoglycemia, hepatomegaly (build-up of glycogen in liver), enlargement of kidney, elevated serum lactate, elevated uric acid, and hypertriglyceridemia.

Question 11

What is pathophysiology of Cory disease?

Answer 11

AKA glycogen storage type III, caused by a defect in the enzyme alpha 1,6-glycosidase, causes milder hypoglycemia, no elevation in lactate levels, no elevation in uric acid.

Question 12

What is pathophysiology of Pompe disease?

Answer 12

AKA glycogen storage disease type II, caused by deficiency of alpha 1,4- glucosidase in the lysosomes, there is infantile type (More severe: severe muscle weakness, cardiomegaly and heart failure, shortened life expectancy) and adult type (no cardiac involvement, gradual onset of skeletal muscle weakness, diaphragm weakness, respiratory failure).

Question 13

What is the rate-limiting enzyme for glycogen synthesis? For glycogenolysis?

Answer 13

For glycogen synthesis: Glycogen synthase. For glycogenolysis: Glycogen phosphorylase.

Question 14

Which enzyme converts glucose-6-phosphate to glucose?

Answer 14

Glucose-6-phosphatase.

Question 15

Which disease has Glycogen phosphorylase deficiency?

Answer 15

McArdle disease.

Question 16

Which disease has glucose-6-phosphatase deficiency?

Answer 16

It is von Gierke disease.

Question 17

Which glycogen storage disease has lactic acidosis, hyperlipidemia, hyperuricemia (gout)?

Answer 17

It is von Gierke disease.

Question 18

Which disease has alpha 1,6-glucosidase deficiency?

Answer 18

Cori disease.

Question 19

Which disease has alpha 1,4-glucosidase deficiency?

Answer 19

Pompe disease.

Question 20

Which glycogen storage disease has cardiomegaly?

Answer 20

Pompe disease (infantile type).

Question 21

Which glycogen storage disease has diaphragm weakness leading to respiratory failure?

Answer 21

Pompe disease, adult type.

Question 22

Which glycogen storage disease has increased glycogen in liver, severe fasting hypoglycemia?

Answer 22

It is von Gierke disease.

Question 23

Which glycogen storage disease has hepatomegaly, hypoglycemia, hyperlipidemia but normal kidneys, lactate and uric acid levels?

Answer 23

Cori disease.

Question 24

Which glycogen storage disease has painful muscle cramps, myoglobinuria w/ strenuous exercise?

Answer 24

McArdle disease.

Question 25

Which glycogen storage disease has severe hepatosplenomegaly, enlarged kidneys?

Answer 25

It is von Gierke disease.

Question 26

What does Glycogen synthase make?

Answer 26

Converts Uridine disphosphoglucose (UDP-glucose) into alpha-1,4 glycosidic linkages.