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Biochem Final > Glycogen > Flashcards

Glycogen Flashcards

1
Q

How can we obtain glucose for the body?

A

The diet
Degradation of glycogen
Gluconeogenesis

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2
Q

Which source of glucose is faster: glycogen synthesis or gluconeogenesis?

A

Glycogen Synthesis

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3
Q

Where is most glycogen found and stored?

A

In the liver or muscle

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4
Q

From what source is the glycogen provided for blood glucose?

A

Liver

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5
Q

How much glycogen is found in muscle?

A

400 g

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6
Q

How much glycogen is found in the liver?

A

100 g

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7
Q

List three properties of Glycogen

A

Branched polysacharide
Alpha (1-4) glycosidic bonds
Branches of Alpha (1-6) glycosidic bonds

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8
Q

Where and how in the cell is glycogen stored?

A

As small granules in the cytoplasm of cells.

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9
Q

What will happen to glycogen stores in the liver while eating?

A

Increase

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10
Q

Glycogen is synthesized from what molecule and what does it require?

A

Alpha-D-Glucose and requires ATP and Uridine Triphosphate (UTP)

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11
Q

One of the first steps is the conversion of Glucose-6-Phosphate to ___________ by the enzyme ___________.

A

Glucose-1-Phosphate by the enzyme Phosphoglucomutase

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12
Q

What enzymes catalyzes the conversion of Glucose-1-Phosphate to UDP-glucose?

A

UDP-glucose pyrophosphoryase

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13
Q

What compound is the source of ALL the glucose residues in the synthesis of glycogen?

A

UDP-glucose

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14
Q

What enzyme makes the chains of alpha(1-4) glycosidic linkages in glycogen? What can it not use?

A

Glycogen synthase - cannot use free glucose to act as an acceptor molecule for UDP-glucose.

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15
Q

What protein will add glucose onto itself? What is this process called?

A

Glycogenin - autoglucosylation

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16
Q

What will glucose use to attach to the glycosylated glycogen?

A

UDP-glucose

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17
Q

When can glycogen synthase start to build the glycogen chain?

A

Once a few monomers of glucose are linked forming a primer.

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18
Q

How is elongation of the glycogen chain happening?

A

Glucose-UDP is transferred to the non-reducing end of the growing chain.

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19
Q

Where will the new glycosidic bond be formed? What is the linkage made by?

A

The anomeric hydroxy group of the UDP-glucose and carbon 4 of the accepting glucose molecule. Made by glycogen synthase.

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20
Q

The released UDP can be phosphorylated by what energy rich compound?

A

ATP

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21
Q

What enzyme is responsible for this to occur?

A

Nucleoside Diphosphate Kinase

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22
Q

What is amylose?

A

Unbranched glucose linked by Alpha (1-4) linkages found in plants.

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23
Q

The branching of glycogen occurs at every __ residues of glucose?

A

8

24
Q

Branching increases the number of non-reducing ends to which new glucose can be added. This greatly speeds up what?

A

The synthesis of glucose.

25
Q

What is the name of the branching enzyme?

A

Amylo-alpha-(1-4) - alpha-(1-6) transglucosidase

26
Q

How does this branching enzyme work?

A

Cleaves off 6-8 glucosyl residues breaking a alpha(1-4) bond in the process.

27
Q

What happens to these glucose residues after being broken off?

A

They are then attached to a non-terminal glucose residue by a alpha-(1-6) linkage.

28
Q

Is the breakdown of glycogen the reversal of the making of glycogen?

A

No

29
Q

When glycogen is broken down the end products are…

A

Glucose-1-phosphate and some free glucose

30
Q

Glucose-1-phosphate is obtained from the breaking down of what type of bonds?

A

Alpha(1-4) glycosidic linkages.

31
Q

How is the free glucose obtained?

A

The breaking down of each alpha(1-6) glycosidic bond.

32
Q

What enzyme will cleave the alpha(1-4) bonds from the non-reducing end?

A

Glycogen Phosphorylase

33
Q

How many glucose units will remain on each chain after the chain is cleaved by glycogen phosphorylase?

A

4

34
Q

What does Glycogen phosphorylase require to function?

A

The co-enzyme pyridoxal phosphate which is Vit B6

35
Q

What is the name of the structure that remains after the glycogen is cleaved?

A

Limit Dextrin and it cannot be degraded further by glycogen phosphorylase.

36
Q

How many enzymatic reactions are required to remove the branches?

A

2

37
Q

The first enzymatic reaction to remove the branches uses what enzyme? How any of the four glucose residues will it remove?

A

oligo-alpha(1-4) - alpha (1-4) glucan transferase. Will remove 3 of the 4 residues

38
Q

Where do the 3 residues get transferred to on another glycogen molecule?

A

To the nonreducing end of another chain lengthening that chain.

39
Q

The single glucose that was not cleaved off by the transferase will be removed by what enzyme? What will it release?

A

amylo-alpha (1-6) glucosidase. Will release free glucose.

40
Q

Where in the cell is glucose-1-phosphate converted to glucose-6-phosphate?

A

Phosphoglucose mutase.

41
Q

The conversion of glucose-1-phosphate to glucose-6 takes place through what intermediate?

A

glucose 1,6 bisphosphate

42
Q

In the liver, glucose-6 phosphate is transported where by glucose-6-phosphate translocase?

A

The endoplasmic reticulum

43
Q

In the endoplasmic reticulum glucose-6-phosphate is converted to glucose by what enzyme?

A

Glucose-6-phosphatase

44
Q

In muscle tissue, where does glucose-6-phosphate enter and why?

A

Glycolysis as muscles lack glucose-6-phosphatase

45
Q

What percent of glycogen is broker down in the lysosomes?

A

1-3%

46
Q

What is the enzyme called that breaks glycogen down in the lysosomes?

A

acid alpha(1-4) glucosidase

47
Q

A deficiency in this enzyme will cause what effect?

A

An accumulation of glycogen in cavuoles in the lysosomes resulting in muscle weakness.

48
Q

About 1 in how many individuals will be born with a glycogen storage disease.

A

40 000

49
Q

GSD 1 is what condition and what enzyme is flawed?

A

Von Gierkes Disease - glucose-6-phosphatase (cannot convert glucose-6-phosphate to glucose)

50
Q

Pompe’s Disease is GSD __ and impacts what specific enzyme?

A

II - acid alpha-glucosidase (causes an accumulation of glycogen in vacuoles within lysosomes = muscle weakness)

51
Q

GSD IV aka? enzyme?

A

Andersen Disease - amylo 1-4, 1-6 transglucosidase

52
Q

Pompe’s disease can also be called?

A

Acid Maltase Deficiency

53
Q

The accumulation of glycogen in the tissue with Pompe’s Disease will give what appearance?

A

Appearance of pseudo-hypertrophic muscles.

54
Q

Pompe’s disease will affect what structures and cause what symptoms in the body?

A

The diaphragm, the heart and tongue are enlarged, lordosis, kyphosis and death is usually by heart failure

55
Q

Andersen’s is described as a bad Cori’s disease and is due to a deficiency in what enzyme?

A

Glycogen branching enzyme amylo1-4, 1-6 transglucosidase.

56
Q

This deficiency will affect glycogen how? What will the clinical symptoms be?

A

Accumulation of abnormal glycogen with long outer branches. Clinical features are muscle hypotonia and Cirrhosis - death from liver disease.

Biochem Final (3 decks)

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