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BGM1002-Biochemistry > BGM1002/L25 Glycogen Metabolism > Flashcards

BGM1002/L25 Glycogen Metabolism Flashcards

1
Q

How many residues are between each branch point in glycogen?

A

10

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2
Q

Why is glucose converted to glycogen? (2)

A

Renal loss
Osmotic pressure

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3
Q

Why is glycogen branched?

A

Facilitates fast mobilisation

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4
Q

Where are the 2 main sites of glycogen storage?

A

Liver and muscle

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5
Q

Which is the largest glycogen store in the body?

A

Muscle

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6
Q

What percentage weight of muscle is glycogen?

A

2%

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7
Q

What is glucose released as in muscle?

A

Glucose-6-phosphate (just for muscle)

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8
Q

Why can’t glucose escape muscle cells?

A

Muscle lacks the enzyme to remove final phosphate group

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9
Q

What percentage by weight of glycogen is the liver?

A

10%

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10
Q

How many kJ/g is glycogen?

A

17

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11
Q

How many kJ/g is fat?

A

37kJ/g

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12
Q

Why does the body favour fat as an energy source?

A

It stores energy more efficiently

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13
Q

How many steps are there to glycogenesis?

A

3

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14
Q

Name the 4 main molecules in glycogenesis.

A

Glucose-6-phosphate
Glucose-1-phosphate
UDP-glucose
Glycogen

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15
Q

Name step 1 of glycogenesis.

A

Diversion
Glucose-6-phosphate -> glucose-1-phosphate

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16
Q

What enzyme is involved in diversion (step 1) of glycogenesis?

A

Phosphoglucomutase

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17
Q

Name step 2 of glycogenesis.

A

Activation
Glucose-1-phosphate -> UDP-glucose

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18
Q

What enzyme is involved in activation (step 2) of glycogenesis?

A

UDP-glucose pyrophosphorylase

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19
Q

What enzyme separates the 2 phosphate groups formed in step 2 of glycogenesis?

A

Inorganic pyrophosphorylase

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20
Q

Name step 3 of glycogenesis.

A

Polymerisation
UDP-glucose -> glycogen

21
Q

What enzyme is involved in polymerisation (step 3) of glycogenesis?

A

Glycogen synthase

22
Q

Name step 4 of glycogenesis.

A

Branching

23
Q

What is the primer required for glycogen synthase?

A

Glycogenin

24
Q

When does glycogenesis usually occur?

A

Post-prandially
Between meals

25
Q

Name the 2 steps of glycogenolysis.

A

Erosion of chain ends
Debranching

26
Q

What enzyme is required for step 1 of glycogenolysis (erosion of chain ends)?

A

Glycogen phosphorylase

27
Q

Which step is the rate-limiting step of glycogenolysis?

A

Step 1: erosion of chain ends

28
Q

How is the activity of glycogen phosphorylase regulated?

A

Controlled by phosphorylation

29
Q

Where does glycogen phosphorylase stop acting?

A

4th glucose-1-phosphate

30
Q

What enzymes are involved in step 2 of glycogenolysis? (2)

A

Alpha-(1->4)-transglycosylase
Alpha-(1->6)-glucosidase

31
Q

What is the role of alpha-(1->4)-transglycosylase?

A

Transfer of 3/4 glucose units to end of the chain

32
Q

What is the role of alpha-(1->6)-glucosidase?

A

Breaking off the last remaining glucose unit from the side chain

33
Q

What is step 3 of glycogenolysis?

A

Recovery
Glucose-1-phosphate -> glucose-6-phosphate

34
Q

What enzyme is involved in step 3 of glycogenolysis?

A

Phosphoglucomutase

35
Q

What is step 4 of glycogenolysis?

A

Release for glycolysis or to the liver

36
Q

What enzyme converts glucose-6-phosphate to glucose?

A

Glucose-6-phosphatase

37
Q

Give 4 symptoms of glycogen storage diseases (GSD).

A

Muscle cramp
Muscle weakness
General tiredness
Hypoglycaemia
Hepatomegally (liver enlargement)

38
Q

What occurs in liver glycogen synthase deficiency?

A

Glycogen can’t be polymerised
Glucose-1-phosphate remains in liver

39
Q

Give 2 symptoms of liver glycogen synthase deficiency.

A

Hyperglycaemia
Hypoglycaemia

40
Q

What occurs in Von Gurke’s Disease (glucose-6-phosphate deficiency)?

A

Final phosphate can’t be converted into glucose
Glucose can’t be deposited back into blood

41
Q

Give 2 symptoms of Von Gurke’s disease.

A

Hypoglycaemia
Hepatomegally

42
Q

What occurs in Cori’s Disease (amylo-1,6-glucosidase deficiency)?

A

Second active site of debrancher
Glycolysis blocked at branches

43
Q

Give 2 symptoms of Cori’s Disease.

A

Hepatomegally
Hypoglycaemia

44
Q

What occurs in Andersen’s Disease (amylo-(1,4->1,6)-glucosidase defiency)?

A

Brancher enzyme
Glucose release insufficiently fast

45
Q

Give 2 symptoms of Andersen’s Disease.

A

Hepatomegally
Hypoglycaemia
Poor prognosis

46
Q

What occurs in McArdle’s Disease (muscle phosphorylase deficiency)?

A

Muscle isoenzyme releases terminal sugars
Muscle requirements not met during exercise

47
Q

Give a symptom of McArdle’s Disease.

A

Muscle cramps/weakness

48
Q

How can glycogen storage diseases be identified?

A

Muscle biopsy

BGM1002-Biochemistry (29 decks)

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