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Gastrointestinal Week 1 2016/17 > 4: Biochemistry - Glycogen metabolism > Flashcards

4: Biochemistry - Glycogen metabolism Flashcards

1
Q

What is glycogenesis?

A

Synthesis of glycogen from glucose

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2
Q

What is glycogenolysis?

A

Breakdown of glycogen to form glucose

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3
Q

What is glycogen?

A

A storage unit of glucose

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4
Q

Where is glycogen found?

A

Liver cells

Muscle cells

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5
Q

The glycogen stored in the liver is stored and then released to maintain an appropriate [X]blood.

Name X.

A

Glucose

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6
Q

Muscle glycogen can:

a) only be consumed within a muscle cell
b) be consumed by the blood to maintain [glucose]

A

a - not available for maintenance of blood glucose

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7
Q

By which process do muscle cells use glycogen?

A

Glycolysis

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8
Q

When would muscle cells use glycogen?

A

During physical activity

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9
Q

Glycolysis allows muscle cells to generate ___.

A

ATP

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10
Q

Dietary carbohydrate contributes to blood sugar levels immediately following ___.

A

meals

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11
Q

Which process maintains blood sugar levels between meals?

A

Glycogenolysis

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12
Q

Which process maintains blood sugar levels when dietary carbohydrate isn’t available and liver glycogen stores have been depleted?

A

Gluconeogenesis

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13
Q

Glycogen is a polymer of which monosaccharide?

A

Glucose

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14
Q

Which bonds form long, straight chains of glucose molecules?

A

α 1-4 glycosidic bonds

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15
Q

Which carbons are bonded to form long, straight glycosidic bonds between glucose in a molecule of glycogen?

A

1 and 4

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16
Q

Which bonds form branches in a glycogen molecule?

A

α​ 1-6 glycosidic bonds

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17
Q

The more ___ a glycogen molecule has, the greater the rate at which glucose can be added or cleaved off it.

A

branches

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18
Q

Which protein, found on glucose chains, acts as a catalyst for glycogen synthesis by forming precursor glycogen molecules?

A

Glycogenin

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19
Q

Which protein is added to a glucose primer before glycogen synthesis?

A

Glycogenin

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20
Q

Before glucose can be used by a cell, it must be (phosphorylated / dephosphorylated) by an enzyme.

What is this enzyme called?

What is the end product of this reaction?

A

phosphorylated

Hexokinase

Glucose-6-phosphate

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21
Q

Which product is formed by the phosphorylation of glucose by hexokinase?

A

Glucose-6-phosphate

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22
Q

If immediate energy is required, glucose-6-phosphate can be used in which process?

A

Glycolysis

23
Q

Name two possible fates of glucose-6-phosphate.

A

Used in glycolysis for immediate energy

or

Stored as glycogen

24
Q

refer to glycogen synthesis diagram

A
25
Q

For each glucose which is added to glycogen, 1 ATP is consumed.

Why?

A

ATP is used to regenerate UDP ⇒ UTP.

26
Q

Which molecule activates glucose-1-phosphate before it is added to glycogen?

What is the name of the activated glucose molecule?

(Which enzyme carries out this process?)

A

UTP

UDP-glucose

(UDP-glucose pyrophosphorylase)

27
Q

Which enzyme adds UDP-glucose to glycogen?

What is a byproduct of this reaction?

A

Glycogen synthase

UDP

28
Q

Before precursor molecules can be used in biochemical processes, they need to be ___.

A

activated

29
Q

Why can UTP be used to transfer glucose to a glycogen molecule?

A

The bond contains a lot of free energy (same concept with ATP)

30
Q

How many glucose molecules are added by each reaction catalysed by glycogen synthase?

A

1

31
Q

Can glycogen synthase introduce branches to a glucose chain?

A

No

32
Q

What is the rate limiting enzyme of glycogenesis?

Why?

A

Glycogen synthase

It can only add on one glucose molecule at a time

33
Q

Which enzyme introduces branches to a glycogen molecule?

A

Transglycosylase

34
Q

Which type of bond introduces branches to a glycogen molecule?

Which enzyme is responsible?

A

α 1-6 glycosidic bonds

Transglycosylase

35
Q

Which process involves the removal of glucose molecules from glycogen?

A

Glycogenolysis

36
Q

Which enzyme removes a glucose molecule from glycogen by adding a phosphate molecule to it?

A

Glycogen phosphorylase

37
Q

Write a word equation for glycogenolysis.

A

[glucose]n + Pi ⇒ [glucose]n-1 + glucose-1-phosphate

38
Q

What is the rate limiting enzyme of glycogenolysis?

Why?

A

Glycogen phosphorylase

It can only remove one glucose molecule at a time

39
Q

How is glucose-1-phosphate prepared for glycolysis following glycogenolysis?

A

It’s converted back into glucose-6-phosphate

40
Q

Which enzyme is responsible for both:

glucose-6-phosphate ⇒ glucose-1-phosphate in glycogenesis

and

glucose-1-phosphate ⇒ glucose-6-phosphate following glycogenolysis?

A

Phosphoglucomutase

41
Q

The liver can dephosphorylate glucose-6-phosphate and release it into the bloodstream as glucose.

Is this glycolysis?

A

No, different shortened process

42
Q

Can skeletal muscle dephosphorylate glucose-6-phosphate as the liver does?

A

No - must go through glycolysis and Kreb’s instead

43
Q

In the liver, which enzyme dephosphorylates glucose-6-phosphate into glucose for the bloodstream?

A

Glucose-6-phosphatase

44
Q

Which transporter, found in liver cells, transports glucose into the blood?

A

GLUT2

45
Q

If glycogenesis and ___ occured at the same rate, the whole process would be pointless.

A

glycogenolysis

46
Q

Which hormone regulates the activity of:

glycogen synthase (glycogenesis)

and

glycogen phosphorylase (glycogenolysis)?

A

Insulin

47
Q

The presence of insulin (stimulates / inhibits) glycogenesis and (stimulates / inhibits) glycogenolysis.

A

stimulates

inhibits

48
Q

Which process and enzyme are stimulated by high insulin levels?

A

Glycogenesis, catalysed by glycogen synthase

49
Q

Which process and enzyme are stimulated by low insulin levels?

A

Glycogenolysis, catalysed by glycogen phosphorylase

50
Q

Which hormone, other than insulin, also affects the rates of glycogenesis and glycogenolysis?

A

Glucagon

51
Q

match levels of insulin and glucagon to inhibition / stimulation of the two processes because they work as a pair

A
52
Q

Which hormones, released in emergencies, stimulate glycogen phosphorylase and therefore glycogenolysis?

A

Adrenaline

Cortisol

53
Q

Glycogen storage disease are associated with (hormone / enzyme) defects.

A

enzyme

Gastrointestinal Week 1 2016/17 (13 decks)

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