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BIOC > Glycogen Metabolism > Flashcards

Glycogen Metabolism Flashcards

1
Q

what is glycogen

A

a polymer of glucose

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2
Q

Why do we need to store glucose

A

1) The brain uses almost exclusivley glucose
2. Glycogen allows ther relase of glucose during fasting state
3. Glycogen can generate ATP without O2
4. Glycogen can be rapidly borken down during times of high activity

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3
Q

What part of the body maintains blood glucose levels

A

the liver

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4
Q

how is glycogen stores in the cytosol

A

as large granules

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5
Q

How many glucose residues in glycogen

A

12-14

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6
Q

how are glucose residues attached in glycogen

A

alpha (1->4) linkage

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7
Q

what linkage is at the 5th of 6th glucose residue

A

alpha (1->6) linkage

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8
Q

how many branch points does glycogen chain have

A

2

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9
Q

What is the characteristic of the glycogen molecule

A

It is polar

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10
Q

Why is the glycogen molecule polar

A

It has a reducing and non reducing ends

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11
Q

What is the reducing end of glycogen

A

has the anomeric carbon ‘ free’

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12
Q

What are the non-reducing ends of gylcogen

A

free 4’ OH

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13
Q

Which ends are multiple

A

non-reducing

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14
Q

why is branching important

A

allows for many non reducing ends which allows for rapid synthesis and breakdown of glycogen

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15
Q

what does an alpha(1->4) linkage cause

A

a slight curve of polymer

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16
Q

what does a beta(1->4) linkage give

A

a straight polymer)

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17
Q

What does phosphoglucomutase cause

A

conversion of glucose-6-phosphate to glucose-1-phosphate

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18
Q

What converts glucose-6-phosphate to glucose-1-phosphate

A

phosphoglucomutase

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19
Q

How do you make an activated form of glucose

A

attach glucose to uridine triphosphate (UTP)

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20
Q

what is the activated form of glucose

A

uridine diphosphate glucose (UDP, glucose, and pyrophosphate)

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21
Q

what catalyzes the formation of UDP

A

UDP glucose, pyrophosphorylate

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22
Q

Why is the formation of UDP ‘irreversible’

A

phosphate is rapidly hydrolized to orthophosphate

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23
Q

What allows the hydrolization of orthophosphate

A

pyrophosphatase

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24
Q

what does glycogen synthase do

A

transfer glucose from UDP glucose to non-reductin end of glycogen chain (results in new alpha(1->4) linkage)

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25
Q

What causes the attachment of glucose to glycogen chain (from UDP)

A

glycogen synthase

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26
Q

what is the final products of glycogen synthesis

A

glycogen (n+1) & UDP

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27
Q

What do branching enzymes do

A

transfer 7 residue glucose residue segments from nonreducing end of an outerchain and forms an alpha (1->6) likage internally to same chain as neighbouring outer chain

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28
Q

what does the branching enzyme cause

A

makes the chain more soluble and creates many non-reducingg ends

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29
Q

what does glycogen phosphorylase do

A

removes a glucose residue form the non-reducing end of glycogen

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30
Q

how is glucose removed from glycogen

A

addition of orthophosphate

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31
Q

what is phosphorolysis

A

removing glucose from glycogen

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32
Q

what is the product of phosphorolysis

A

glucose-1-phosphate and glycogen

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33
Q

does phosphorolysis require ATP (why or why not)

A

no -> ratio of orthophosphate much larger

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33
Q

Debranching - what does transferase do

A

shifts 3 residues from one branch to another

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34
Q

what does alpha-1,6-glucose do

A

cleaves the remaining alpha(1->6) residues using water -> yielding glucose

35
Q

name the two enzymes in debranching

A

transferase and alpha-1,6-glucose

36
Q

what converts glucose-1-phosphate to glucose-6-phosphate

A

phosphoglucomutase

37
Q

what does phosphoglucomutase do

A

converts glucose-1-phosphate to glucose-6-phosphate

38
Q

what is the final product of glycogen breakdown

A

glucose-6-phosphate

39
Q

what are the fates of glucose-6-phosphate

A
  1. glycolysis
  2. dephosphorylation by glucose-6-phosphate and release into bloodstream of liver
  3. pentose phosphate pathway: generates ribose and NADPH
40
Q

what is gluconeogenesis

A

process of generating glucose from non-carbohydrate precursors

41
Q

where does gluconeogenesis occur

A

liver and kidney (NOT muscles)

42
Q

what molecules can be used to make glucose

A
  1. Lactate/pyruvate
  2. Proteins (amino acids)
  3. Glycerol
43
Q

what happens to lactate/pyruvate in gluconeogenesis in the liver

A
  1. Liver takes it up, converts it into pyruvate, and then back to glucose
44
Q

what happens to lactate/pyruvate in gluconeogenesis in the heart

A
  1. Heart can take up lactate, convert it into pyruvate, and oxidize it to CO2 and H2O
45
Q

what cycle does lactate/pyruvate go through in gluconeogenesis

A

cori cycel

46
Q

what are amino acids broken into during gluconeogenesis

A

pyruvate or krebbs cycle intermediates

47
Q

why are amino acids broken down into krebbs cycel intermediates during gluconeogenesis

A

oxaloacetate is in the 2nd step of gluconeogensis

48
Q

what is the krebs cycle intermediate that cannot be used to make oxaloacetate

A

acety CoA (it is irreversible –> can’t be converted back to pyruvate)

49
Q

what is glycerol converted into in gluconeogenesis

A

glycerol -> glycerol phosphate ->DHAP

50
Q

why is gluconeogenesis no the reversal of glycolysis

A

the 3 irreversile steps of glycolysis

51
Q

What is bypass reaction number 1 of gluconeogenesis

A

converting phosphoenol pyruvate from pyruvate

52
Q

what are the 2 steps of bypass reaction number 1

A
  1. Conversion of pyruvate to oxaloacetate
  2. Conversion of oxaloactetate to phosphoenol pyruvate
53
Q

what converts pyruvate to oxalloacetate

A

pyruvate carboxylase

54
Q

what does pyruvate carboxylase require

A

biotin (small molecuels that traps and binds CO2)

55
Q

where does gluconeogensis occur

A

cytosol

56
Q

where does conversion of pyruvate to oxaloacteate occur

A

matrix

57
Q

how is oxaloacetate transported to the cytosol

A

malate translocase –> converts oxaloactetate to malate, goes out to cytsol, and converted back to oxaloacetate

58
Q

what converts oxaloacetate to phosphoenolpyruvate

A

phosphoenolpyruvate carboxykinase

59
Q

what does phosphoenol pyruvate carboxykinase do

A

converts oxaloacetate to phosophoenolpyruvatte

60
Q

what is consumed in the phosphoenol pyruvate carboxykinase reaction

A

1 GTP

61
Q

what is bypass reaction 2 of gluconeogenesis

A

generation of fructose-6-phosphate from fructose-1,6,bisphosphate

62
Q

what enzyme allows the generation of fructose-6-phosphate

A

fructose1,6,bisphosphotase

63
Q

what is special about fructose1,6,bisphosphotase

A

it is a key regulatory enzyme

64
Q

what is bypass reaction 3 of gluconeogenesis

A

generation of free glucose

65
Q

what is the enzym in bypass reaction 3 of gluconeogenesis

A

glucose-6-phosphotase

66
Q

what does glucose-6-phosphotase do

A

hydrolyzes the phosphate off glucose-6-phosphate

67
Q

glycolysis and gluconeogenesis are:

A

reciprocally regulated

68
Q

what inhibits fructose 1,6, bisphosphotase

A

AMP and Fructose 2,6, bisphosphate

69
Q

what activates fructose 1,6, bisphosphotase

A

citrate

70
Q

what inhibits phosphoenol pyruvate carboxykinase

A

ADP

71
Q

what activates phosphoenol pyruvate carboxykinase

A

nothing!

72
Q

what activates pyruvate carboxylase

A

Acetyl CoA

73
Q

what inhibits pyruvate carboxylase

A

ADP

74
Q

what are ketone bodies

A

they are the way the liver shiips acetyl units from acetyl CoA to the rest of the body

75
Q

high blood glucose

A

hyperglycemia

76
Q

low blood glucose

A

hypoglycemia

77
Q

what is insulin

A

peptide hormone released when glucose levels in the blood are high

78
Q

what is glucagon

A

peptide hormone secreted when glucose is scarce

79
Q

what produces insulin

A

beta islet cells in the pancrease

80
Q

what does insulin promote

A

1) uptake of glucose
2) synthesis of glycogen, fats, and proteins

81
Q

what does glucagon promote

A

1) lipolysis
2) switch to using fatty acids for fuels in most cells
3) glycogen breakdown and gluconeogensis

82
Q

where is glucagon produced

A

alpha islet cells of pancrease

83
Q

what is epinephrine

A

a catecholomine hormone released when glucose is needed in a stress situaiton

84
Q

what does epinephrine target

A

mainly tissues, but muscles are also key target

BIOC (4 decks)

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