Brainscape's Knowledge GenomeTM

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


See full index

Biochem > Chapter 24 > Flashcards

Chapter 24 Flashcards

1
Q

what is the structure of glycogen?

A

highly branched homopolymer of glucose
nonreducing ends of the glycogen molecule form the surface of the glycogen granule
the protein glycogenin is at the core

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

why is glucose a more versatile energy source than fatty acids?

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

where are the largest stores of glycogen found?

A

the liver and skeletal muscles

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

where is glycogen found?

A

in all tissues

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

what does the liver do to glycogen?

A

the liver breaks down glycogen and releases glucose to the blood

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

why does the liver release glucose to the blood?

A

to provide energy for the brain and red blood cells during nocturnal fasts

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

what happens to muscle glycogen stores?

A

muscle glycogen stores are mobilized to provide energy for muscle contraction

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

why does glucose glycogen cleaved in the muscle stay in the muscle?

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

where does glycogen degradation take place on the molecule?

A

at the surface

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

what does the protein glycogenin do?

A

it is a primer that begins glycogen degredation

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

what does glycogen phosphorylase do?

A

degrades glycogen from the nonreducing ends of the glycogen molecule and catalyzes a phosphorolysis reaction to create glucose 1-phosphate

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

what does glycogen phosphorylase cleave?

A

α-1,4-glycosidic bonds

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

what does transferase do?

A

shifts a small oligosaccharide near the branch point to a nearby chain

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

what is the purpose of the transferase moving the oligosaccharide near the branch point?

A

to make the glucose moieties accessible to the phosphorylase

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

what does α-1,6 glucosidase do?

A

cleaves the α-1,6 linkage at the branch point and releases a free glucose

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

is the reaction of glycogen to glucose favorable or unfavorable?

A

favorable

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

what does phosphoglucomutase do?

A

converts glucose 1-phosphate into glucose 6-phosphate

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

what happens when the free glucose is phosphorylated by hexokinase?

A

it produces glucose 6-phosphate

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

what does phosphoglucomutase do?

A

it forms glucose 6-phosphate from glucose 1-phosphate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

what does phosphoglucomutase use to form glucose 6-phosphate?

A

glucose 1,6-bisphosphate intermediate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What does glucose 6-phosphatase do in the liver?

A

it generates free glucose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what happens to the free glucose created from the Calvin cycle?

A

the free glucose is released into the blood for use by other tissues such as the brain and red blod cells

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

what is the liver’s role in the body’s glucose levels?

A

to maintain a nearly constant concentration of glucose in the blood

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what is the default state of liver phosphorylase?

A

The α form in the R state

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

___ is a negative regulator of liver phosphorylase

A

Glucose

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
26
Q

how does glucose regulate liver phosphorylase?

A

by facilitating the transition from the R state to the T state

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
27
Q

what kind of enzymes are liver phosphorylase and muscle phosphorylase?

A

isozymes

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
28
Q

when is phosphorylase inactive?

A

when blood glucose is high

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
29
Q

what happens to phosphorylase in the T state?

A

the active site is partly blocked by a regulatory structure

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
30
Q

what happens to phosphorylase in the R state?

A

the active site is unobstructed

31
Q

what is the default form of phosphorylase in the muscle?

A

the b form in the T state (unphosphorylated)

32
Q

what is the predominant form of phosphorylase in the liver?

A

the a form in R state (phosphorylated)

33
Q

what doesn’t contribute to regulation of phosphorylase a in the liver?

A

AMP, ATP, and glucose 6-phosphate

34
Q

what inhibits phosphorylase a and how?

A

glucose; it pushes it into the T state

35
Q

what happens to phosphorylase b when energy is needed in the muscle?

A

the phosphorylase binds AMP, which stabilizes the R state

36
Q

what signals to phosphorylase b that energy is needed in the muscle?

A

an increase in the concentration of AMP

37
Q

what stabilizes the T state of phosphorylase in the muscle?

A

ATP and glucose 6-phosphate

38
Q

what does increasing energy demands do to phosphorylase?

A

it activates signal transduction pathways to phosphorylate b to a

39
Q

what are the characteristics of phosphorylase a?

A

phosphorylated
usually active
R state
predominates in the liver

40
Q

what are the characteristics of phosphorylase b?

A

not phosphorylated
usually inactive
T state
predominates in the muscle

41
Q

what are the characteristics of liver glycogen phosphorylase?

A 
default state is a
allosterically regulated by glucose 
doesn't use much ATP
insensitive to AMP
R state
42
Q

what does the allosteric regulation of liver glycogen phosphorylase by glucose do?

A

binding of glucose to phosphorylase causes shift from R to T state

43
Q

why is muscle glycogen phosphorylase insensitive to glucose?

A

muscle uses glucose especially during exercise

44
Q

what promotes the conversion of phosphorylase b to phosphorylase a?

A

phosphorylation

45
Q

what is the difference between the two forms of phosphorylase?

A

b form is less active

a form is more active and has a phosphorylated serine residue 14

46
Q

what stimulates phosphorylation of phosphorylase?

A

the hormones glucagon and epinephrine

47
Q

what does phosphorylation do to phosphoryalase?

A

it alters the active site such that alpha helices that partially block the active site in the b form are removed

48
Q

how is phosphorylase kinase activated in the muscle?

A

by phosphorylation and calcium ion binding

49
Q

what is phosphorylase kinase responsible for?

A

it is the enzyme responsible for the conversion of glycogen phosphorylation from the unphosphorylated b state to the a state

50
Q

what phosphorylates phosphorylase kinase?

A

protein kinase A

51
Q

what is the delta subunit of phosphorylase?

A

the calcium sensor calmodulin

52
Q

when is phosphorylase kinase maximally active?

A

when phosphorylated and bound to calcium

53
Q

what are type I muscle fibers?

A

slow twitch fibers

rely primarily on cellular respiration as a means of generating ATP

54
Q

what are type IIb muscle fibers?

A

fast twitch fibers
rely primarily on lactic acid fermentation for ATP generation
rich in glycogen phosphorylase

55
Q

what are type IIa muscle fibers?

A

have biochemical characteristics intermediates between the other fiber types

56
Q

what muscle fiber type does glycogen not play a role in?

A

Type I

57
Q

is the slow twitch highly dependent on glycolysis?

A

NO

58
Q

what causes hers disease?

A

a deficiency in the liver isozyme of glycogen phosphorylase

59
Q

what happens to a person suffering from Hers disease?

A

glycogen accumulates in the liver (hepatomegaly) and hypoglycemia results

60
Q

what causes both manifestations in Hers disease?

A

an inability to mobilize glycogen

61
Q

what initiates Glycogen breakdown?

A

G proteins transmit the signal for initiation of glycogen breakdown

62
Q

how does the initiation of glycogen breakdown begin?

A

glucagon (in liver) and epinephrine (in muscle) initiate G-protein cascades that result in production of cAMP (the Beta-adrenergic receptor)

63
Q

in the initiation of glycogen breakdown, what initiates the activation of phosphorylase kinase in the muscle?

A

calcium, released in muscle to stimulate contraction

64
Q

in the initiation of glycogen breakdown in the liver, how is Ca2+ released?

A

Ca2+ release is stimulated by epinephrine binding to the α-adrenergic receptor

65
Q

in the initiation of glycogen breakdown in the liver, what happens after calcium is released?

A

it activates a G-protein and instigates the phosphoinositide cascade

66
Q

what does cyclic AMP do in the initiation of glycogen breakdown?

A

cyclic AMP activates protein kinase A

67
Q

what does protein kinase A do in the initiation of glycogen breakdown?

A

it phosphorylates and completes activation of phosphorylase kinase

68
Q

what does phosphorylase kinase do in the initiation of glycogen breakdown?

A

it converts glycogen phosphorylase b to the a form, activating glycogen degradation

69
Q

what are the general steps in the initiation of glycogen breakdown in the muscle?

A
  1. epinephrine (muscle) initiate G-proteins
  2. G-protein cascades result in cAMP
  3. calcium, released to stimulate contraction, initiates activation of phosphorylase kinase
  4. cAMP activates protein kinase A
  5. protein kinase A phosphorylates and completes activation of phosphorylase kinase
  6. phosphorylase kinase converts glycogen phosphorylase b to a
  7. glycogen degradation is activated
70
Q

what are the general steps in the initiation of glycogen breakdown in the liver?

A
  1. glucagon (muscle) initiates G-proteins
  2. G-protein cascades result in cAMP
  3. epinephrine binds to the alpha0adrenergic receptor and stimulates release of Ca2+
  4. calcium release activates G-protein and instigates phosphoinositide cascade
  5. cAMP activates protein kinase A
  6. protein kinase A phosphorylates and completes activation of phosphorylase kinase
  7. phosphorylase kinase converts glycogen phosphorylase b to a
  8. glycogen degradation is activated
71
Q

what are the mechanisms that shut down glycogen breakdown?

A

as hormone levels decrease

  1. the inherent GTPase activity of the G protein renders these proteins inactive
  2. phosphodiesterase converts cAMP into AMP, which does not stimulate protein kinase A
  3. Protein phosphatase 1 (PP1) removes phosphoryl groups from phosphorylase kinase and glycogen phosphorylase, inactivating the enzymes
72
Q

what happens to G proteins during shut down of glycogen degredation?

A

inherent GTPase activity of G proteins renders the proteins inactive

73
Q

how does the stimulation of protein kinase A stop during shut down of glycogen degredation?

A

phosphodiesterase converts cAMP into AMP, which doesn’t stimulate protein kinase A

Biochem (12 decks)

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