Brainscape's Knowledge GenomeTM

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


See full index

Biochem > Chapter 25 > Flashcards

Chapter 25 Flashcards

1
Q

what is UDP-glucose?

(uridine diphosphate glucose)

A

activated form of glucose
the glucose donor in glycogen synthesis

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

what synthesizes UDP-glucose?

A

by UDP-glucose pyrophosphorylase

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

what renders the synthesis of UDP-glucose irreversible?

A

the hydrolysis of pyrophosphate

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

how is UDP-glucose synthesized?

A

UDP-glycose pyrophosphorylase hydrolyzes UTP and puts it in glucose

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

what drives the synthesis of UDP-glucose reaction to the right?

A

the cleavage of PPi

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

what does glycogen synthase do in the reaction of Glucose to UDP-glucose?

A

glycogen synthase catalyzes the transfer of glucose from UDP-glucose to a growing chain

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

what does glycogen synthase do in the synthesis of glycogen?

A

it transfers a glucose moiety from UDP-glucose to the C-4 terminal residue of a glycogen chain to form an α-1,4-glycosidic bond

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

what does glycogen synthase require as a primer?

A

an oligosaccharide of glucose residues

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

what synthesizes the primer needed by glycogen synthase?

A

glycogenin

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

what is glycogenin?

A

a dimer of two identical subunits

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

what does each subunit of glycogenin do?

A

each subunit generates an oligosaccharide of glucose residues 10-20 molecules long

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

what does glycogen synthase do to the primer?

A

it extends the primer

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

glycogen synthase can only synthesize what kind of linkages?

A

α-1,4-linkages

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

what does a branching enzyme do?

A

it generates branches allowing glycogen synthase to extend the branch polymer

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

how does a branching enzyme create branches?

A

it generates branches by cleaving an α-1,4-linkage and taking a block of approximately 7 glucoses and synthesizing an α-1,6-linkage,

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

what does the branching of an enzyme allow?

A

increase insolubility
increases ends for synthesis and degradation

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

when is glycogen synthase inactive?

A

when in the phosphorylated b form

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

when is glycogen synthase active?

A

in the unphosphorylated a form

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

what is the key regulatory process of glycogen synthesis?

A

the conversion of the b form in the T state to the active R state by binding glucose 6-phosphate

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

what is the difference between phosphorylation of glycogen synthase and glycogen phosphorylase?

A

it has opposite effects
glycogen phosphorylase is phosphorylated and active in a form and unphopshorylated in b form
glycogen synthase is phosphorylated in b form and unphosphorylated in a form

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

Quick quiz: why is the fact that phosphorylation has opposite effects on glycogen synthesis and breakdown advantageous?

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

what inhibits glycogen synthesis?

A
  • phosphorylation of glycogen synthase by protein kinase A (PKA) to form glycogen synthase b
  • phosphorylation by glycogen synthase kinase (GSK)
23
Q

what does insulin do to glycogen synthesis pathways?

A

it turns on pathways to store glucose

24
Q

when levels of glucagon and epinephrine GO UP do you want to turn on synthesis of glycogen or turn it off?

A
25
Q

what happens during the FED state?

A

there is high glucose levels

26
Q

what happens during the FASTING state?

A

there are low glucose levels

27
Q

how does the regulation of protein phosphatase 1 in muscle take place?

A
  • Phosphorylation of Gm by protein kinase A dissociates the catalytic subunit from its substrates in the glycogen particle
  • Phosphorylation of the inhibitor subunit by protein kinase A inactivates catalytic unit of PP1
28
Q

what does protein phosphatase 1 (PP1) do to the glycogen metabolism?

A
  • it shifts glycogen metabolism from the degradation mode to the synthesis mode
  • it removes phosphoryl groups from glycogen synthase b, converting it into the more active a form
  • it removes phosphoryl groups from the phosphorylase kinase and glycogen phosphorylase, inhibiting glycogen degradation?
29
Q

how does PP1 inhibit glycogen degredation?

A

it removes phosphoryl groups from phosphorylase kinase and glycogen phosphorylase

30
Q

how does insulin stimulate glycogen synthesis?

A

by activating a signal transduction pathway that results in the phosphorylation and inactivation of glycogen synthase kinase

31
Q

what does PP1 do to glycogen synthase?

A

is dephosphorylates glycogen synthase, generating the active a form of the synthase, activating it and allowing glycogen synthesis

32
Q

how does insulin facilitate glycogen synthesis?

A

by increasing the number of glucose transporters (GLUT4) in the plasma membrane

33
Q

what does insulin do to glycogen synthase kinase?

A

insulin triggers a cascade that leads to the phosphorylation and inactivation of glycogen synthase kinase and prevents the phosphorylation of glycogen synthase

34
Q

what does glycogen metabolism in the liver regulate?

A

blood-glucose levels

35
Q

how do high blood-glucose levels effect glycogen degradation and synthesis?

A

degradation in the liver is inhibited

synthesis is stimulated

36
Q

what does the binding of glucose to glycogen phosphorylase do?

A

it converts glycogen phosphorylase a from the R state to the T state

37
Q

what does the conversion of glycogen phosphorylase a from R to T state by glucose cause?

A

the activation of PP1 that is associated with the phosphorylase

38
Q

what does PP1 do to the glycogen metabolism?

A

it converts the glycogen metabolism from a degradation mode to a synthesis mode

39
Q

what is the first step in glucose regulation of liver-glycogen metabolism?

A

glucose binds to glycogen phosphorylase a and inhibits it, facilitating the formation of the T state of phosphorylase a

40
Q

what does the T state of phosphorylase a cause in the liver?

A

The T state of phosphorylase a does not bind protein phosphatase 1 (PP1), leading to the dissociation of PP1 from glycogen phosphorylase a, and its activation

41
Q

what does the free PP1 do to the liver-glycogen metabolism?

A

it dephosphorylates glycogen phosphorylase a and glycogen synthase b, leading to the inactivation of glycogen breakdown and the activation of glycogen synthesis

42
Q

how does glucose regulate liver-glycogen metabolism

A
  1. glucose binds glycogen phosphorylase, inhibiting it
  2. inhibition of glycogen phosphorylase causes formation of T state of phosphorylase a
  3. T state of phosphorylase a does not bind protein phosphatase 1 (PP1)
  4. PP1 dissociates from glycogen phosphorylase a, activating it
  5. free PP1 dephosphorylates glycogen phosphorylase a and glycogen synthase b
  6. glycogen breakdown is inactivated
  7. glycogen synthesis is activated
43
Q

what do phosphorylase and synthase activity depend on in the liver?

A

glucose

44
Q

as glucose increases, phosphorylase activity….

A

decreases

45
Q

as glucose increases, synthase activity….

A

increases

46
Q

at low glucose __ is active

A

phosphorylase

47
Q

at high glucose, ___ is active

A

synthase

48
Q

what is diabetes?

A

it is characterized by the presence of excess glucose and underutilization of the fuel

49
Q

where is excess glucose secreted in people with diabetes?

A

urine

50
Q

what is type 1 diabetes (T1D)?

A

childhood onset

insulin is not produced

51
Q

how is type 1 diabetes managed?

A

injection of insulin

52
Q

what is type 2 diabetes (T2D)?

A

insulin is produced by the insulin-signaling pathway is not responsive, a condition referred to as insulin resistance

53
Q

how is type 2 diabetes managed?

A

diet

Biochem (12 decks)

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