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Biochemistry > Metabolism 5 (glycogenesis + glycogenolysis) > Flashcards

Metabolism 5 (glycogenesis + glycogenolysis) Flashcards

1
Q

What is glycogenesis?

A

Formation of glycogen

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2
Q

What is glycogen?

What is the name of its protein core?

A

Polysaccharide
Glucose molecules bound by alpha 1,4 glycosidic linkages

Glycogenin

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3
Q

Where does glycogenesis occur?

What does it prevent?

A

Liver + muscle

Hyperglycaemia

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4
Q

Which type of glucose transporter is in:
> pancreas?
> liver?
> muscle?

A

GLUT2

GLUT2

GLUT4

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5
Q

Describe how glycogenesis is initiated in liver + muscle in the fed state

A
  1. Glucose in blood rises
  2. Transported to pancreas via GLUT2
  3. Beta cells secrete insulin
  4. Glucose transported to hepatocytes (GLUT2) + muscle cells (GLUT4)
  5. Glucose in liver + muscle increases
  6. Insulin stimulates glycogenesis in muscle + liver
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6
Q

How does insulin affect the glucose transporters in muscle cells?

A

Increases the no. of GLUT4 bound to the plasma membrane

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7
Q

What affects the storage + release of glycogen in the liver?

What is this glycogen used by?

A

Changes in blood glucose levels

NOT the liver
- glucose released into blood for other tissues to use

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8
Q

What does glycogen support in muscle cells?

What is this glycogen used by?

A

Aerobic + anaerobic energy conversion pathways

Muscle cells only
DON’T release glucose back into blood

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9
Q

What does the pathway that synthesises glycogen use?

A

Activated glucose
= UDP-glucose
= Uridine diphosphate glucose

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10
Q

Which is the rate limiting enzyme in glycogenesis?

What does this enzyme catalyse?

A

Glycogen synthase

Formation of alpha 1,4 linkages

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11
Q

Why is branching in glycogen important?

A

> increases solubility

> more branches = glucose can be released more readily

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12
Q

What does a branching enzyme catalyse?

A

Formation of alpha 1,6 linkages

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13
Q

What does glycogen phosphorylase target?

A

Alpha 1,4 glycosidic linkages

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14
Q

At which stage does glycogenolysis finish in the muscle?

What then happens to the final product?

A

G-6-P

G-6-P taken on to the glycolytic pathway

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15
Q

At which stage does glycogenolysis finish in the liver?

What then happens to the final product?

A

Glucose

Released into blood

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16
Q

How is glycogen metabolism regulated?

A

Covalent modification

Allosteric control

17
Q

What is glycogen synthase activated by?

What does this do to the enzyme?

A

Insulin

Dephosphorylates

18
Q

What is glycogen synthase inhibited by?

What does this do to the enzyme?

A

Glucagon

Phosphorylates

19
Q

What is glycogen phosphorylase activated by?

What does this do to the enzyme?

A

Glucagon

Phosphorylates

20
Q

What is glycogen phosphorylase inhibited by?

What does this do to the enzyme?

A

Insulin

Dephosphorylation

21
Q

What are the 3 glycogen phosphorylase inhibitors in the liver?

A

ATP
G6P
Glucose

22
Q

What are the 2 glycogen phosphorylase inhibitors in muscle?

A

ATP

G6P

23
Q

What are the glycogen phosphorylase activators in muscle?

A

AMP

Ca2+

24
Q

What is the glycogen synthase activator in liver?

A

G6P

25
Q

What is the glycogen synthase activator in muscle?

A

G6P

26
Q

What are glycogen storage diseases?

A

A class of more than 10 distinct disorders of glycogen metabolism

  • characterised by increased or decreased amounts of glycogen
  • affect mainly liver + muscle
27
Q

What is the rate limiting enzyme of glycogenolysis?

A

Glycogen phosphorylase

28
Q

What is the 1st step of glycogenesis?

A

Glucose -> G6P

Via hexokinase
or glucokinase in liver

29
Q

What is the 2nd step of glycogenesis?

A

G6P -> G1P

Via Phosphoglucomutase

30
Q

What is the 3rd step of glycogenesis?

A

G1P -> UDP-glucose

Via UDP-glucose pyrophosphorylase

31
Q

What is the 4th step of glycogenesis?

A

UDP-glucose -> glycogen (alpha 1,4)

Via glycogen synthase

Using a glycogen primer

32
Q

What is the glycogen primer made of?

A

Glycogenin + UDP-Glucose

33
Q

What is the 5th step of glycogenesis?

A

Glycogen (alpha 1,4) -> glycogen (alpha 1,6)

Via branching enzyme

34
Q

What is the 1st step of glycogenolysis?

A

Glycogen -> G1P

Via glycogen phosphorylase (1,4)
+ Transferase
+ Debranching enzyme (1,6)

35
Q

What is the 2nd step of glycogenolysis?

A

G1P -> G6P

Via Phosphoglucomutase

36
Q

What is the 3rd step of glycogenolysis?

A

G6P -> Glucose

Via G6Pase

Biochemistry (14 decks)

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