Glycogen Metabolism

Question 1

This is the storage form of carbohydrates in animals.

Answer 1

Glycogen

Question 2

What are the primary storage sites of glycogen?

Answer 2

Liver and skeletal muscle

Question 3

This type of glycogen is more sensitive to dietary carbohydrates and is synthesized more rapidly following post-exercise glycogen depletion.

Answer 3

Proglycogen

Question 4

This type of glycogen has a much slower and constant synthesis. It is responsible for carbohydrate loading (supercompensation).

Answer 4

Macroglycogen

Question 5

How many grams of glycogen can skeletal muscle hold? Can it release glucose?

Answer 5

400 grams and skeletal muscle cannot release glucose

Question 6

How many grams of glycogen can the liver hold? Can it release glucose?

Answer 6

100 grams and the liver can release glucose

Question 7

Where would you store your glycogen?

Answer 7

Cytosol

Question 8

What is the general mechanism for glycogen synthesis?

Answer 8

• Phosphorylate glucose
• Make UDP-glucose
• Initation
• Elongation of the chain
• Branching

Question 9

This is a protein that starts the glycogen chain with the amino acid tyrosine.

Answer 9

Glycogenin

Question 10

What is the enzyme that starts the glycogen chain?

Answer 10

Glycogen initiator synthase

Question 11

When you are resynthesizing glycogen you are using what?

Answer 11

ATP

Question 12

How many ATPs are broken down to attach each glucose for glycogen synthesis?

Answer 12

3

Question 13

What is the enzyme, type of bonds created, and location of elongation of a glycogen chain?

Answer 13

Glycogen synthase adds alpha (1–>4) bonds in the cytosol

Question 14

What is the enzyme and type of bonds created in the branching phase of glycogen synthesis?

Answer 14

Glucosyl 4:6 transferase adds alpha (1–>6) bonds

Question 15

What enzyme degrades glycogen?

Answer 15

Glycogen phosphorylase

Question 16

After glycogen has been degraded into glucose 1P what enzyme converts it into glucose 6P?

Answer 16

Phosphoglucomutase

Question 17

When is glycogen phosphorylase no longer effective at breaking down glycogen?

Answer 17

When there are four glucose molecules left prior to a branch point

Question 18

When glycogen phosphorylase is no longer effective, two new enzymes are required to continue glycogen degradation. What are they?

Answer 18

• Glucosyl (4:4) transferase: removes the outer three glucose molecules
• Amylo-alpha-(1,6)-glucosidase: removes the last glucose of the branch

Question 19

What are the main regulating enzymes of glycogen synthesis?

Answer 19

Glycogen synthase (sitmulates) and glycogen phosphorylase (inhibits)

Question 20

What does exercise do to GLUT4, glycogen synthesis, and insulin sensitivity?

Answer 20

GLUT4: increased translocation and increased amount of transporters
Glycogen synthesis: stimulated after exercise
Insulin sensitivity: increased after exercise

Question 21

This phase of glycogen synthesis occurs 30-60 minutes after exercise, is insulin independent, and occurs when muscle glycogen levels are relatively low and carbohydrates are provided immediately after exercise.

Answer 21

Rapid phase

Question 22

This phase of glycogen synthesis occurs several hours after exercise, is insulin dependent, is a much slower rate of glycogen synthesis, and must have carbohydrates and insulin available.

Answer 22

Slow phase

Question 23

What are the two phases of increased glucose uptake?

Answer 23

Insulin-independent: <3-6 hours post exercise, AMPK pathway stimulated, P13K pathway is temporarily inhibited.
Insulin-dependent: 3-6 to 48 hours post-exercise

Question 24

Does consumption of carbohydrates after exercise increase glycogen synthesis?

Answer 24

Yes

Question 25

Is glycogen storage higher in trained athletes than the normal individual?

Answer 25

Yes

Question 26

This is the increased in blood glucose level over the base-line level during a 2 hour period following the consumption of a defined amount of carbohydrate compared with the same amount of carbohydrate in a reference food.

Answer 26

Glycemic index

Question 27

This term is used to describe the glycemic index times the grams of carbohydrate in a serving of the food. It considers both the quantity and the quality of the carbohydrate in a meal.

Answer 27

Glycemic load

Question 28

The ____ the glycemic load, the ____ the expected elevation in blood glucose and in the insulinogenic effect of the food.

Answer 28

Higher; greater

Question 29

What factors are involved with the synthesis of glycogen?

Answer 29

- High blood glucose - Insulin - Fructose (impacts liver not muscle) - Low glycogen content - High Energy Charge - ATP

Question 30

What factors are involved with the breakdown of glycogen?

Answer 30

- Low Blood Glucose (impacts liver not muscle) - Glucagon (impacts liver not muscle) - Low Energy Charge - ADP, AMP - Calcium (muscle contraction)