Glycogen

Question 1

What are the major tissue types where glycogen is produced?

Answer 1

Liver and Muscle.

Question 2

Which tissue directly contributes to blood glucose levels?

Answer 2

Liver.

Question 3

Which tissue is insulin dependent for glucose uptake? Independent?

Answer 3

Dependent: Adipose and Muscle
Independent: Liver, Brain.

Question 4

Describe the events in insulin release after a meal and the cellular response.

Answer 4

1. Insulin binds to receptor in cell membrane
2. receptor promotes recruitment of vesicles containing glucose transporters to the cell membrane
3. Vesicles fuse to membrane, increasing amount of glucose transporters in the membrane.

Question 5

What is activated in order to assist the vesicles containing glucose transporters to move towards the cell membrane?

Answer 5

Protein Kinase B (PKB)

Question 6

When insulin levels are low, how do muscle cells circumvent this problem in order to recruit glucose transporters to the membrane?

Answer 6

Use ATP to up AMP levels, which stimulates AMP-kinase and promotes the translocation of the transporters.

Question 7

How is exercising in diabetes patients beneficial?

Answer 7

Because muscles can circumvent the lack of insulin and continue to transport glucose.

Question 8

What is the common first step in all glucose related pathways? Results in what kind of molecule?

Answer 8

The phosphorylation of glucose to give Glucose 6-P. This is a highly polar charged molecule that cant escape the cell.

Question 9

What is the first reaction formula in glucose pathway? Catalysts?

Answer 9

Glucose + ATP= Glucose 6-P and ADP. Catalyzed y Hexokinase and Glucokinase.

Question 10

What are the characteristics of Hexokinase (tissue, Levels, Affinity, Inhibited)?

Answer 10

1. In general tissue
2. Constitutive enzyme
3. Low Km (High affinity for glucose)
4. Inhibited by product

Question 11

What are the characteristics of Glucokinase (tissue, Levels, Affinity, Inhibited)?

Answer 11

1. In liver only
2. Induced Enzyme
3. high Km (low affinity for glucose)
4. Not inhibited by product

Question 12

How is glucokinase regulated? What two molecules stimulate its release?

Answer 12

In a fasting state, Glucokinase is bound to GKRP and inactive in the nucleus of the cell. Glucose and Fructose1-P can stimulate its release from GKRP.

Question 13

What is gluconeogenesis?

Answer 13

The process of making Pyruvate into Glucose during low levels of blood glucose.

Question 14

Describe the process of Glycogenesis from glucose. What type of bonds is the result?

Answer 14

1. Glucose+ ATP= Glucose 6-P
2. Glucose 6-P–>Glucose 1-P
3. UTP + Glucose 1-P= UDP-Glucose and 2Pi
4. UDPG with Glycogen Synthase–>UDP and transfers Glucose to the non-reducing end of a glycogen primer.
   alpha-1,4 bonds are the result in the chain.

Question 15

How is UTP regenerated?

Answer 15

ATP is used to create UTP from UDP.

Question 16

How many ATP is used per glucose molecule in glycogenesis?

Answer 16

2 ATP

Question 17

What is Glycogenin? What is it used for? What type of bonds?

Answer 17

Is a dimer with tyrosine residues arranged head to toe. It transfers glucose from UDP-G to create glycogen chain when a glycogen fragment is absent to accept the glucose. a-1,4 bonds

Question 18

How are branches formed in glycogen formation?

Answer 18

Branching enzymes transfer a group of 5-8 glucoses in the chain to a more interior side and links it with a a-1,6 bond.

Question 19

How is glycogenolysis achieved in a non-branching glycogen chain?

Answer 19

Glycogen Phosphorylase cleaves a glucose molecule from the non-reducing ends of the glycogen chain. It then phosphorylates that glucose created Glucose 1-P.

Question 20

How is glcogenolysis achieved at a glycogen branching point?

Answer 20

De-branching enzyme uses transferase to transfers a group of 3 glucoses to an a jointing chain. It then uses glucosidase to hydrolyze the remaining a-1,4 bond, freeing that glucose.

Question 21

What enzyme will convert Glucose 6-P into glucose in the liver only?

Answer 21

glucose 6-Phosphatase

Question 22

What does glycogen phosphorylase do? Glycogen Synthase? When are they active?

Answer 22

1. Phosphorylase: Converts glycogen into Glucose1-P, active during fasting state.
2. Synthase: Adds glucose onto growing glycogen chains. Active during well fed state.

Question 23

Phosphorylated Glycogen synthase is active or inactive? P-Glycogen phosphorylase?

Answer 23

Synthase-P=Inactive

Phosphorylase-P= Active

Question 24

How is Glycogen Phosphorylase phosphorylated? Un-P?

Answer 24

Phosphorylase kinase phosphorylates (activates).

Phosphotase removes P (Inactivates).

Question 25

What three kinases can Glycogen Synthase be Phosphorylated by?

Answer 25

1. Protein Kinase A (PKA)
2. Phosphroylase Kinase
3. GSK-3

Question 26

What 2 hormones are activators of glycogenolysis? Characteristics (origin, tissue)?

Answer 26

1. Glucagon: From alpha cells in pancreas, In liver only

2. Epinephrine: Secreted by adrenal medulla during stress, trauma, physical activity. In muscle and liver.

Question 27

Describe the activation of Protein Kinase A pathway.

Answer 27

1. Glucogon or epi binds to G-protein receptor
2. Adenylyl cyclase converts ATP to cAMP
3. cAMP activates PKA
4. PKA activates phosphorylase, de-activates synthase

Question 28

What does insulin do to Adenylate cyclase activity?

Answer 28

It blocks its activity. This causes phosphorylation activity to cease.

Question 29

What is the Insulin Glucogon ration equation?

Answer 29

Blood Glucose=Rate of Supply/Rate of Removal=Glucagon,Epi,Cortisol,CH,TH/Insulin