EXAM3_Glycogen_Metabolism Flashcards Preview

BIOCHEMISTRY > EXAM3_Glycogen_Metabolism > Flashcards

Flashcards in EXAM3_Glycogen_Metabolism Deck (15)
1

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

100grams of glycogen stored in liver
Will last about 30 hours

2

How much muscle glycogen is stored?

400 grams stored in muscle
Lasts weeks- b/c not used anywhere except the muscle

3

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

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

4

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

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

5

What are the three regulatory enzymes of Glycogenesis?
Which one is rate limiting enzyme ?

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

6

What core protein and amino acid required for glycogenesis?

Glycogenin & Tyrosine

7

Glycogenolysis 3 enzymes?
What is rate limiting?

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

8

What should you think when you see Glycogen phosphorylase?

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

9

Debranching Enzyme

-removes outer 3 glucosyl residues
-glucose released

10

What enzyme converts G1P to G6P?

G6Pase (liver and renal cortex)
-free glucose released (maintains blood glucose fasting)

11

What is the significance of exercising muscle glycogenolysis?

G6P enters glycolysis directly (skipping ATP fee)
-also primes TCA

12

Muscle glycogenolysis is crucial for TCA cycle priming. How?

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

13

During intense exercise where does muscle get its energy from?

Beta Oxidation- not from complete oxidation of glucose

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

14

Glycogen synthase Activation/Inhibition in the Muscle

Activated by insulin (dephosphorylated form is active)
Inhibited by Epinephrine

15

Glycogen synthase Activation/Inhibition in the Liver

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