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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
What causes the attachment of glucose to glycogen chain (from UDP)
glycogen synthase
26
what is the final products of glycogen synthesis
glycogen (n+1) & UDP
27
What do branching enzymes do
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
28
what does the branching enzyme cause
makes the chain more soluble and creates many non-reducingg ends
29
what does glycogen phosphorylase do
removes a glucose residue form the non-reducing end of glycogen
30
how is glucose removed from glycogen
addition of orthophosphate
31
what is phosphorolysis
removing glucose from glycogen
32
what is the product of phosphorolysis
glucose-1-phosphate and glycogen
33
does phosphorolysis require ATP (why or why not)
no -> ratio of orthophosphate much larger
33
Debranching - what does transferase do
shifts 3 residues from one branch to another
34
what does alpha-1,6-glucose do
cleaves the remaining alpha(1->6) residues using water -> yielding glucose
35
name the two enzymes in debranching
transferase and alpha-1,6-glucose
36
what converts glucose-1-phosphate to glucose-6-phosphate
phosphoglucomutase
37
what does phosphoglucomutase do
converts glucose-1-phosphate to glucose-6-phosphate
38
what is the final product of glycogen breakdown
glucose-6-phosphate
39
what are the fates of glucose-6-phosphate
1. glycolysis 2. dephosphorylation by glucose-6-phosphate and release into bloodstream of liver 3. pentose phosphate pathway: generates ribose and NADPH
40
what is gluconeogenesis
process of generating glucose from non-carbohydrate precursors
41
where does gluconeogenesis occur
liver and kidney (NOT muscles)
42
what molecules can be used to make glucose
1. Lactate/pyruvate 2. Proteins (amino acids) 3. Glycerol
43
what happens to lactate/pyruvate in gluconeogenesis in the liver
1. Liver takes it up, converts it into pyruvate, and then back to glucose
44
what happens to lactate/pyruvate in gluconeogenesis in the heart
2. Heart can take up lactate, convert it into pyruvate, and oxidize it to CO2 and H2O
45
what cycle does lactate/pyruvate go through in gluconeogenesis
cori cycel
46
what are amino acids broken into during gluconeogenesis
pyruvate or krebbs cycle intermediates
47
why are amino acids broken down into krebbs cycel intermediates during gluconeogenesis
oxaloacetate is in the 2nd step of gluconeogensis
48
what is the krebs cycle intermediate that cannot be used to make oxaloacetate
acety CoA (it is irreversible --> can't be converted back to pyruvate)
49
what is glycerol converted into in gluconeogenesis
glycerol -> glycerol phosphate ->DHAP
50
why is gluconeogenesis no the reversal of glycolysis
the 3 irreversile steps of glycolysis
51
What is bypass reaction number 1 of gluconeogenesis
converting phosphoenol pyruvate from pyruvate
52
what are the 2 steps of bypass reaction number 1
1. Conversion of pyruvate to oxaloacetate 2. Conversion of oxaloactetate to phosphoenol pyruvate
53
what converts pyruvate to oxalloacetate
pyruvate carboxylase
54
what does pyruvate carboxylase require
biotin (small molecuels that traps and binds CO2)
55
where does gluconeogensis occur
cytosol
56
where does conversion of pyruvate to oxaloacteate occur
matrix
57
how is oxaloacetate transported to the cytosol
malate translocase --> converts oxaloactetate to malate, goes out to cytsol, and converted back to oxaloacetate
58
what converts oxaloacetate to phosphoenolpyruvate
phosphoenolpyruvate carboxykinase
59
what does phosphoenol pyruvate carboxykinase do
converts oxaloacetate to phosophoenolpyruvatte
60
what is consumed in the phosphoenol pyruvate carboxykinase reaction
1 GTP
61
what is bypass reaction 2 of gluconeogenesis
generation of fructose-6-phosphate from fructose-1,6,bisphosphate
62
what enzyme allows the generation of fructose-6-phosphate
fructose1,6,bisphosphotase
63
what is special about fructose1,6,bisphosphotase
it is a key regulatory enzyme
64
what is bypass reaction 3 of gluconeogenesis
generation of free glucose
65
what is the enzym in bypass reaction 3 of gluconeogenesis
glucose-6-phosphotase
66
what does glucose-6-phosphotase do
hydrolyzes the phosphate off glucose-6-phosphate
67
glycolysis and gluconeogenesis are:
reciprocally regulated
68
what inhibits fructose 1,6, bisphosphotase
AMP and Fructose 2,6, bisphosphate
69
what activates fructose 1,6, bisphosphotase
citrate
70
what inhibits phosphoenol pyruvate carboxykinase
ADP
71
what activates phosphoenol pyruvate carboxykinase
nothing!
72
what activates pyruvate carboxylase
Acetyl CoA
73
what inhibits pyruvate carboxylase
ADP
74
what are ketone bodies
they are the way the liver shiips acetyl units from acetyl CoA to the rest of the body
75
high blood glucose
hyperglycemia
76
low blood glucose
hypoglycemia
77
what is insulin
peptide hormone released when glucose levels in the blood are high
78
what is glucagon
peptide hormone secreted when glucose is scarce
79
what produces insulin
beta islet cells in the pancrease
80
what does insulin promote
1) uptake of glucose 2) synthesis of glycogen, fats, and proteins
81
what does glucagon promote
1) lipolysis 2) switch to using fatty acids for fuels in most cells 3) glycogen breakdown and gluconeogensis
82
where is glucagon produced
alpha islet cells of pancrease
83
what is epinephrine
a catecholomine hormone released when glucose is needed in a stress situaiton
84
what does epinephrine target
mainly tissues, but muscles are also key target

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