EXAM3_Glycogen_Metabolism

Question 1

How much liver glycogen is stored? How long will that battery last?

Answer 1

100grams of glycogen stored in liver

Will last about 30 hours

Question 2

How much muscle glycogen is stored?

Answer 2

400 grams stored in muscle

Lasts weeks- b/c not used anywhere except the muscle

Question 3

High IG ratio has what effect on glycogen in the liver?

Answer 3

GLUT2 uptake from portal circulation
Glucokinase (High KmVmax) Traps glucose inside liver
-liver stores 100g glycogen

Question 4

High IG ratio has what effect on glycogen in muscle and adipose?

Answer 4

GLUT4 uptake from systemic circulation
Hexokinase traps glucose in peripheral tissue cells
Muscle glycogenesis up to 400g stored

Question 5

What are the three regulatory enzymes of Glycogenesis?

Which one is rate limiting enzyme ?

Answer 5

1. UDP-glucose pyrophosphorylase,
2. Glycogen synthase**, (Rate limiting)
3. Branching enzyme

Question 6

What core protein and amino acid required for glycogenesis?

Answer 6

Glycogenin & Tyrosine

Question 7

Glycogenolysis 3 enzymes?

What is rate limiting?

Answer 7

1. Glycogen phosphorylase* (rate limiting)
2. Debranching Enzyme
3. G6Pase

Question 8

What should you think when you see Glycogen phosphorylase?

Answer 8

• alpha 1,4 cleavage (glycosidic bond)
• requires Pi
• VitB6 is coenzyme (Pyridoxal phosphate)
• Glucose 1-P is product
• 4 glucosyl units

Question 9

Debranching Enzyme

Answer 9

• removes outer 3 glucosyl residues

- glucose released

Question 10

What enzyme converts G1P to G6P?

Answer 10

G6Pase (liver and renal cortex)

-free glucose released (maintains blood glucose fasting)

Question 11

What is the significance of exercising muscle glycogenolysis?

Answer 11

G6P enters glycolysis directly (skipping ATP fee)

-also primes TCA

Question 12

Muscle glycogenolysis is crucial for TCA cycle priming. How?

Answer 12

G6P converted to Pyruvate which is converted to OAA (in the TCA)

Question 13

During intense exercise where does muscle get its energy from?

Answer 13

Beta Oxidation- not from complete oxidation of glucose

Muscle glycogenolysis required to prime TCA for beta oxidation to work?

Question 14

Glycogen synthase Activation/Inhibition in the Muscle

Answer 14

Activated by insulin (dephosphorylated form is active)

Inhibited by Epinephrine

Question 15

Glycogen synthase Activation/Inhibition in the Liver

Answer 15

Activated by Insulin

Inhibited by Epinephrine AND GLUCAGON (phosphorylated form b is INACTIVE)