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Glycogen Synethesis And Mobilisation Flashcards

1
Q

What is glucose converted to when it enters a cell

A

Glucose-6-phosphate

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2
Q

What is glycogen

A

Branched Polysaccharide made up of monomers of glucose

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3
Q

What organs is glycogen stored in

A

Liver and muscles

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4
Q

What is glycogen in the liver used for

A

Maintaining blood glucose

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5
Q

What is glycogen in the muscles used for

A

Supply energy during contraction

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6
Q

What term energy store is glycogen

A

Short-medium

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7
Q

How is glycogen found in the body

A

Hydrated granules

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8
Q

Why is glycogen stored instead of glucose

A

Less osmotically active,

Easier to metabolise quickly

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9
Q

Why does glycogen act as a glucose buffer

A

Quick mobile source of glucose

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10
Q

Why is glycogen stored instead triglycerides

A

Can be metabolised in anaerobic conditions

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11
Q

What bonds are in glycogen molecules

A

Alpha 1,4 glycosidic,

1,6 glycosidic

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12
Q

How many glucose residues are in a glycogen molecule

A

10000 - 40000

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13
Q

How many reducing ends does glycogen have

A

1

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14
Q

Why does glycogen have many non reducing ends

A

Increases synthesis and breakdown speed By giving More sites for enzymes to work on

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15
Q

Where are enzymes involved in glycogen synthesis and breakdown found

A

Outer branches of glycogen molecules

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16
Q

What is the primer for glycogen synthesis

A

Glycogenin

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17
Q

What is glycogenin

A

Primer for glycogen,
Dimer,
Starting protein first glucose can bind to to start glycogen chain

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18
Q

Which enzyme synthesises glycogen

A

Glycogen synthase

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19
Q

Glycogen starting materials

A

Glycogenin primer,

Glucose 6 phosphate

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20
Q

What state must glucose be in before being added to glycogen

A

Glucose 6 phosphate

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21
Q

First step of glycogen synthesis

A

Mutase converts glucose 6 phosphate into glucose 1 phosphate

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22
Q

2nd step of glucose synthesis after Mutase converts glucose 6 phosphate into glucose 1 phosphate

A

Glucose 1 phosphate converted to UDP-glucose by hydrolysis with UTP

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23
Q

3rd step of glycogen synthesis after Glucose 1 phosphate converted to UDP-glucose by hydrolysis with UTP

A

UDP-glucose added to glycogen chain by glycogen synthase

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24
Q

Action of glycogen synthase

A

Catalyses 1,4-glycosidic bond formation

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25
Step 4 of glycogen synthesis after UDP-glucose added to glycogen chain by glycogen synthase
Branches added by branching enzyme creating 1,6 bonds
26
Action of branching enzyme
Catalyses formation of 1,6 glycosidic bonds
27
How does glycogen synthase catalyse 1,4 bond formation
Transfers glucose from UDP-glucose to C4 -OH group on non reducing end of glycogen
28
What is the activated form of glucose for biosynthesis
UDP-glucose
29
How many phosphate anhydride bonds are involved in the addition of each glucose to glycogen
2
30
How is glycogen stored
Macroglycogen
31
What is glycogenolysis
Breakdown of glucose
32
Which 3 enzymes control glycogenolysis
Alpha-1,6-glucosidase/ debranching enzyme, Glycogen phosphorylase, Phosphoglucomutase
33
First step of glycogenolysis
Breakdown of glycogen branches by debranching enzyme
34
2nd step of glycogenolysis after Breakdown of glycogen branches by debranching enzyme
Removal of terminal glucose molecules by glycogen phosphorylase
35
Action of glycogen phosphorylase
Breaks 1,4 bonds
36
Step 3 of glycogen breakdown after Removal of terminal glucose molecules by glycogen phosphorylase
Conversion of glucose 1 phosphate to glucose 6 phosphate by phosphoglucomutase
37
What happens in the liver to glucose 6 phosphate removed from glycogen
Phosphate removed by glucose 6 phosphatase a free glucose released into the blood
38
When debranching enzyme take over from glycogen phosphorylase in glycogen breakdown
4 glucose residues before branch point
39
What does debranching enzyme do when glycogen phosphorylase reaches 4 residues before branch point in glycogen breakdown
Transfers 3 glucose residues before the branch to a non reducing end, Removes single residue left before branch point and releases as free glucose
40
When is glucose 6 phosphate de phosphorylated in the liver
Periods of fasting
41
Why is glucose 6 phosphate from glycogen never converted to glucose
Does directly into glycolysis
42
How is lactate produced by glycolysis in anaerobic respiration recycled
Cori cycle
43
Which 4 hormones/signalling molecules control glycogen synthesis and breakdown
Insulin, Glucagon, Adrenaline, Calcium
44
How do adrenaline and calcium act on muscles during activity to control glycogen synthesis and breakdown
Alpha and beta adrenergic receptors
45
How does insulin stimulate glycogen production
Activates glycogen synthase, Inhibits glycogen phosphorylase, Reverses cAMP induced phosphorylation
46
Does insulin stimulate glycogen synthesis or breakdown
Synthesis
47
Does glucagon stimulate glycogen synthesis or breakdown
Breakdown
48
How does glucagon stimulate glycogen breakdown
Inhibits glycogen synthase, | Activates glycogen phosphorylase
49
What molecule does insulin act via to control glycogen synthesis and breakdown
Protein phosphatase
50
What does protein phosphatase do
Removes phosphates from molecules
51
How does protein phosphatase activate glycogen synthase
Removes phosphate group
52
How does protein phosphatase deactivate glycogen phosphorylase
Removes phosphate group
53
Does protein phosphatase add or remove phosphate groups
Remove
54
Does protein kinase add or remove phosphates
Adds
55
Which molecules do glucagon and adrenaline control glycogen synthesis and breakdown through
cAMP, Phosphorylase kinase, Protein kinase,
56
Do protein kinase A and phosphorylase kinase add or remove phosphate groups
Add
57
How do adrenaline and glucagon inhibit glycogen synthesis
Activates glycogen synthase, | Inhibits glycogen phosphorylase
58
How is glycogen synthase activated
Removal of phosphate, | Protein phosphatase
59
How is glycogen phosphorylase activated
Addition of phosphate, Protein kinase a, Phosphorylase kinase
60
Is glycogen synthase phosphorylated in its inactive phase
Yes
61
Is glycogen phosphorylase phosphorylated in its inactive phase
No
62
How does cAMP control glycogen synthesis and breakdown
Activates protein kinase a and phosphorylase kinase
63
How does insulin carry our reciprocal control
Activates phosphodiesterase enzymes that break down cAMP in the cytosol, switching off enzyme activity controlled by glucagon/adrenaline/calcium
64
Where does glucagon control glycogen breakdown and synthesis
Liver
65
Where do adrenaline and calcium control glycogen synthesis and breakdown
Muscle
66
When does most glycogen breakdown occur
Exercise
67
What enzyme can glucose 6 phosphate act as an allosteric activator for
Glycogen synthase
68
How are glycogen storage diseases inherited
Autosomal recessive
69
Why do different glycogen storage diseases affect different parts of the metabolic system
Affect different isoforms of enzymes
70
How are glycogen storage diseases characterised
Hepatic, Myopathic, Generalised
71
What gene is mutated in McArdles disease
Muscular glycogen phosphorylase / myophosphorylase / PYGM gene
72
Why does McArdles disease cause muscle weakness
Cannot break down glycogen in muscle
73
Which enzyme does McArdles disease cause a deficiency in
Myophosphorylase
74
What happens when a patient with McArdles disease does rapid exercise
Muscle damage, Cramping, locking
75
What is the advantage of glycogen being branched
Can be synthesised and broken down rapidly
76
How is glycogen branching achieved
Branching enzyme takes ~7 glucose residues from end of a non branched chain and transfers it to a carbon 6 in another location forming a 1,6 bond

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