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Biomolecular Mechanisms > Week 14: Glycogenesis & Glycogenolysis > Flashcards

Week 14: Glycogenesis & Glycogenolysis 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

When glucose levels are low

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3
Q

What is glycogen?

A

Main storage form of glucose in liver and muscle cell

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4
Q

When is liver glycogen broken down?

A

between meals

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5
Q

Why is liver glycogen released?

A

released to maintain blood glucose levels for red blood cells and brain

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6
Q

What type of glycogen maintains blood glucose levels?

A

liver glycogen

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7
Q

When does muscle glycogen provide energy?

A

during bursts of physical activity

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8
Q

What influences glycogenolysis activity?

A

fluctuates depending on meal times

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9
Q

Recall where glycogenolysis fluctuates?

A
  • Decreases at breakfast but increases shortly after
  • peaks at lunch
  • decreases in-between
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10
Q

What happens to the % of source of blood sugar according to dietary?

A

after meal time increases

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11
Q

What is the primary source of glucose overnight?

A

gluconeogenesis

when hepatic glycogen is depleted

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12
Q

What are the monomers of glycogen?

A

glucose molecules joined by alpha 1-4 glycosidic links

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13
Q

What link are the branches of glycogen on?

A

introduced by alpha-1,6 glycosidic links

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14
Q

What is the nonreduing end of glycogen?

A

provides directionality to glycogen

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15
Q

What are the two pathways glucose-6-phosphate can go?

A
  1. glycolysis

2. glucose-1 phosphate –> glycogen synthesis

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16
Q

What can glucose residues only be added to?

A

existing glycogen chain

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17
Q

What is the intermediate form of glucose?

A

UDP-glucose

active form of glucose

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18
Q

What does the activated form of glucose allow it to do?

A

joining to existing form of glycogen

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19
Q

What does a glycogen residue require to bind to glycogen chain?

A

a certain amount of glycogen to be present i.e glycogen primer

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20
Q

How many glucose residues does a glucose primer contain?

A

4

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21
Q

What is the primer attached to?

A

covalently attached to a protein called glycogenin

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22
Q

What enzyme converts G6P to G1P?

A

phosphoglucomutase

transfers phosphate on C6 to C1

23
Q

What converts G1P to UDP-glucose

A

UDP-glucose pyrophosphorylase

24
Q

What enzyme converts UDP-glucose to glycogen?

A

glycogen synthase

25
Q

What can simple precursors be first converted to?

A

activated intermediates

26
Q

Is G1P+UTP –> UDP+ pyrophosphate (PPi) reversible?

A

YES

27
Q

What pulls the formation of UDP glucose forward?

A

the very active pyrophosphatase hydrolyses PPi so cant reverse anymore

28
Q

What is the rate limiting enzyme of glycogen synthesis?

A

glycogen synthase

29
Q

Can glycogen synthase introduce branches?

A

can not introduce branches

can not start new molecules

30
Q

How many glucose molecules can glycogen synthase add to glycogen?

A

1 at s time

31
Q

What is the branching enzyme?

A

transglycosylase

32
Q

What bond will transglycoylse add a glucose?

A

alpha 1,6-glycosidic linkage on carbon 6

33
Q

How often is a new branch created?

A

every 10 glucose residues

34
Q

What regulates glycogenesis?

A

insulin & glucagon

35
Q

What regulates level of the hormone?

A

stimuli= blood glucose levels

36
Q

When does glycogenesis occur?

A

immediately after meals

37
Q

What is high blood glucose levels also called?

A

hyperglycaemia

38
Q

What hormone activates glycogen synthase? hyperglycaemia

A

insulin

39
Q

What hormone inactivates glycogen synthase? hypoglycaemia

A

glucagon

40
Q

What is glycogenolysis?

A

When we need to utilise the energy stored as glycogen

41
Q

What catalyses glycogenolysis?

A

glycogen phosphorylase

42
Q

What is the rate limiting step in glycogenolysis?

A

degradation of glucose to glucose-1-phosphate& then G6P

43
Q

How many glucose molecules can be cleaved at a a time?

A

1

44
Q

What happens when G6P is dephosphorylated in the liver?

A

dephosphorylated to glucose and released into blood stream

45
Q

Can (skeletal) muscle cells dephosphorylate G6P?

A

NO, instead used to provide energy via glycolysis & TCA cycle

46
Q

What does glycogenolysis depend on?

A

demand for blood glucose

47
Q

What hormones regulate glycogenolysis?

A

hypoglycaemia, stress+hypoglycaemia, stress, hyperglycaemia

48
Q

What is the source of glucagon?

A

pancreatic alpha cells

49
Q

What hormones increases blood glucose levels in glycogenolysis?

A

glucagon, adrenaline, cortisol

50
Q

What hormones decreases blood glucose levels in glycogenolysis?

A

insulin

51
Q

What is the source of insulin?

A

pancreatic beta cells

52
Q

What is the source of adrenaline?

A

adrenal medulla

53
Q

What is the source of cortisol?

A

adrenal cortex

Biomolecular Mechanisms (34 decks)

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