glycogen

Question 1

Glycogen synthase is regulated by what

Answer 1

insulin (stimulates)
glucagon (inhibits)
in the liver and muscle

Question 2

How does glucagon turn off glycogen synthase

Answer 2

• glucagon goes to the liver stimulates beta adrenergic rec
• Gs recepter
• adenylate cyclase
• cAMP
• protein kinase A
• phosporylates glycogen synthase

Question 3

What is the major enzyme of glycogen breakdown

Answer 3

glycogen phosphorylase

Question 4

glycogen phosphorylase is regulated by what

Answer 4

glucagon (liver)
epinephrine (liver, muscle)
AMP (muscle)
all stimulate it

Question 5

Where is glucose-6-phosphatase

Answer 5

in the liver

-takes phosphate off so glucose can go into the blood

Question 6

What enzyme is defective in Von Gierke disease (type I)

Answer 6

glucose-6-phosphatase in the liver

• hallmark is severe hypoglycemia
• lactic acidosis
• hepatomegaly
• hyperlipidemia
• hyperuricemia
• short stature
• doll like face
• protruding abdomen
• emaciated extremities

Question 7

is glycogen synthesis normal in von gierke

Answer 7

yes

Question 8

What will von gierke not affect

Answer 8

muscle

Glucose-6-phosphatase is only in liver

Question 9

Why is there hyperlipidemia in von gierke

Answer 9

secondary to severe hypoglycemia

• turn on hormone sensitive lipase
• breakdown TG to FFA

Question 10

Why is there hepatomegaly in von gierke

Answer 10

glucose cannot get out and backs up in cell

-glucose and glycogen are osmotic and bring in water

Question 11

What defect is in Pompe disease (type II)

Answer 11

lysosomal alpha, 4-glucosidase

hallmark cardiomegaly

• muscle weakness
• death by 2 years

Question 12

Cardiomegaly is associated with which glycogen storage disease

Answer 12

Pompe (type II)

lysosomal alpha, 4-glucosidase

Question 13

What defect is in Cori disease (type III)

Answer 13

glycogen deb ranching enzyme

• mild hypoglycemia
• liver enlargement

Question 14

what defect is in Andersen disease (type IV)

Answer 14

Branching enzyme

• hallmark infantile hypotonia
• cirrhosis
• death by 2 years old

Question 15

which two glycogen storage disease have death by 2 years old

Answer 15

Pompe (type II) - lysosomal alpha, 4 glucosidase

Andersen (type IV) - branching enzyme

Question 16

Which glycogen storage disease have abnormal glycogen structure

Answer 16

Cori (type III)

Andersen (type IV)

Question 17

What is the glycogen structure in Cori disease

Answer 17

defect in glycogen deb ranching enzyme

-shorter outer branches with single glucose residue alpha 1, 6 at outer branch

Question 18

What is the glycogen structure in Andersen disease

Answer 18

defect in branching enzyme

• very few branches especially toward peripherally
• very linear appearing

Question 19

What defect is in McArdle disease (type V)

Answer 19

muscle glycogen phosphorylase

• elevated glycogen in muscle only
• muscle cramps and weakness w/exercise
• myoglobinuria

Question 20

What defect is in Hers disease (type VI)

Answer 20

hepatic glycogen phosphorylase

• mild fasting hypoglycemia
• hepatomegaly
• cirrhosis

Question 21

In which glycogen storage diseases is glycogen structure normal

Answer 21

Von gierke (type I)
pompe (type II)
McArdle (type V)
Hers (type VI)

Question 22

Why is there only mild hypoglycemia in Hers disease

Answer 22

hepatic glycogen phosphorylase breaks down glycogen to G-6-P

-glucose can still get into blood by gluconeogenesis

Question 23

Why is there severe hypoglycemia in von gierke disease

Answer 23

glucose-6-phosphate is trapped in the liver without glucose-6-phosphatase

• need phosphatase to get G6P from gluconeogenesis too
• both paths are blocked

Question 24

In starvation a small amount of glucose can be made in the

Answer 24

kidney