Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Biochemistry: Exam 3 > Control of Glycogen Metabolism > Flashcards

Control of Glycogen Metabolism Flashcards

1
Q

What are the two types of control of the pathways for the synthesis and breakdown of glycogen?

A

1) Allosteric

2) Hormonal control by covalent modification

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Which enzyme in glycogen metabolism is activated allosterically by AMP? Which pathway is it the RDS in?

A

Glycogen phosphorylase; it is part of the glycogenolysis pathway (breaks down glycogen)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Which enzyme is activated by G6P? Which pathway is it part of?

A

Glycogen synthase; it is part of the glycogen synthesis pathway.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

Which molecules inhibit glycogen phosphorylase and, therefore, the breakdown of glycogen?

A

ATP and G6P

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

How does a low concentration of ATP affect glycogen metabolism?

A

It stimulates glycogen phophorylase and, therefore, glycogen breakdown

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

How do high concentrations for AMP affect glycogen metabolism?

A

Activates glycogen phosphorylase and, therefore, the breakdown of glycogen.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

How do low concentrations of G6P affect metabolism of glucose?

A

Inhibits glycogen synthase and, therefore, inhibits glycogen synthesis.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

How do high concentrations of G6P and ATP affect glycogen metabolism?

A

Activates glycogen synthase and inhibits glycogen phosphorylase, thereby stimulating glycogen synthesis.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What molecules move glycogen phosphorylase from the T to the R form?

A

AMP

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What molecules move glycogen phosphorylase from the R to the T form?

A

ATP and G6P

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

True or false: glucose moves glycogen phosphorylase from the T to the R form.

A

False: glucose moves phosphorylase from the R to the T form

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

True or false: Phosphorylase a is only active when it has been covalently modified?

A

False; it is active even without covalent modification

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

True of false: Glycogen synthase is essentially inactive unless it has been dephosphorylated (covalently modified) and G6P is present.

A

True

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What kind of control does the concentration of AMP exert on glycogen phosphorylase?

A

Allosteric control

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What kind of control does phosphorylase kinase and phosphoprotein phosphatase exert on glycogen phosphorylase?

A

Covalent modification

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How does covalent modification affect the control provided by allosteric affectors?

A

It provides sophisticated control that modulates the enzyme’s responsiveness to allosteric effectors.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How is the interconversion of a and b forms of phosphorylase and synthase accomplished?

A

By hormone regulated enzyme catalyzed phosphorylation and dephosphorylation.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What is the result of phosphorylation on glycogen phosphorylase?

A

b form (inactive) goes to a form (active)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What is the result of phosphorylation on glycogen synthase?

A

a form goes to b form

20
Q

What is the result of dephosphorylation on glycogen synthase?

A

b form (inactive) goes to a form (active)

21
Q

What is the net result of dephosphorylation on glycogen phosphorylase?

A

a form goes to b form

22
Q

Which hormones control glycogen metabolism in the liver?

A

Insulin and glucagon (synthesized in the pancreas)

23
Q

Which hormones controls glycogen metabolism in muscles and other tissues?

A

Insulin and epinephrine/norepinephrine

24
Q

In which direction is the metabolic flux when a large fraction of glycogen enzymes are phosphorylated?

A

Toward glycogen breakdown (phosphorylase is active and synthase is inactive)

25
Q

What happens when the concentration of cAMP drops?

A

phosphorylation rate decreases, synthase is activated, and metabolic flux moves toward glycogen synthesis

26
Q

What does the binding of glucagon on a liver cell result in?

A

Generates intracellular cAMP, and results in glucose mobilization from glycogen.

27
Q

When is glucose release from the pancrease?

A

When [blood glucose] is less than 5 mM

28
Q

True or false: Glucagon causes muscle cells to convert glycogen into glucose.

A

False; muscle cells do not have glucagon receptors and do not, therefore, respond to glucagon.

29
Q

What is the second messenger of alpha-adrenergic receptors?

A

Ca2+

30
Q

What is the second messenger of beta-adrenergic receptors?

A

cAMP

31
Q

Which types of cells have both beta- and alpha-adrenergic receptors?

A

liver

32
Q

Which types of cells have only beta adrenergic receptors?

A

muscle

33
Q

True or false: Muscle cells respond to epinephrine.

A

True (via beta-adrenergic receptors)

34
Q

What does epinephrine and norepinephrine cause in muscle cells?

A

Break down glycogen for glycolysis, thereby generating ATP, and helps muscles cope with stress.

35
Q

What effect does epinephrine and norepinephrine have on the liver?

A

Promotes the release of glucagon from the pancreas and, therefore, the breakdown of glycogen to glucose in liver cells.

36
Q

True or false: epinephrine binds only beta-adrenergic receptors.

A

False; it binds both beta and alpha adrenergic receptors.

37
Q

What does the binding of epinephrine by beta-adrenergic receptors cause?

A

Release of cAMP and glycogen breakdown.

38
Q

What does the binding of epinephrine by alpha-adrenergic receptors cause?

A

Stimulates release of Ca2+, reinforcing the cell’s response to cAMP and inactivating glycogen synthase.

39
Q

True or false: Insulin and epinephrine are antagonists.

A

True

40
Q

What triggers the release of insulin?

A

High blood glucose

41
Q

Which types of cells have both insulin receptors and insulin-sensitive GLUT 4? Which do not?

A

Muscle and fat; liver and brain

42
Q

What happens to cAMP when insulin concentration increases? What affect does this have on glycogen metabolism?

A

cAMP concentration decreases; causes glycogen metabolism to shift from breakdown to synthesis.

43
Q

What does insulin promote in muscle?

A

Glucose storage as glycogen by stimulation of synthesis and inhibition of breakdown.

44
Q

What does insulin promote in liver?

A

Glycogen synthesis

45
Q

True or false: Glucose activates phosphorylase in the liver by binding to the R state.

A

False; it inhibits phosphorylase by binding to the T state.

46
Q

Which organs do glycogen storage diseases usually affect?

A

The liver (cause hepatomegaly and hypoglycemia)

47
Q

What affect do glycogen storage diseases have on muscle?

A

Cramps and weakness

Biochemistry: Exam 3 (23 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions