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Semester 2-MEH > Session 4-Energy Storage (Glycogen And Fat) > Flashcards

Session 4-Energy Storage (Glycogen And Fat) Flashcards

1
Q

Which tissues have an absolute requirement for glucose as an energy source? (4)

A

1) red blood cells
2) neutrophils
3) innermost cells of kidney medulla
4) lens of eye

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2
Q

Define glycation

A

Addition of glucose to protein without enzymatic regulation

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3
Q

What is the normal blood glucose concentration?

A

~5mmol/L

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4
Q 
What are the consequences of the following blood glucose concentrations:
A) 2.8 mmol/L
B) 1.7 mmol/L
C) 1.1 mmol/L
D) 0.6 mmol/L
A

A) confusion
B) weakness, nausea
C) muscle cramps
D) brain damage, death

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5
Q

What is glycogen stored as?

A

Granules

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6
Q

Glycogen is a polymer consisting of chains of which residues?

A

Glucose

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7
Q

The chains of glycogen are branched and originate from a dimer of which protein?

A

Glycogenin

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8
Q

Which reactions in glycogenesis require energy and which enzymes catalyse these reactions? (2)

A

1) glucose + ATP -> glucose-6-phosphate + ADP
Catalysed by hexokinase (glucokinase in liver)
2) glucose-1-phosphate + UTP + water -> UDP-glucose + PPi
Catalysed by G1P uridylyltransferase

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9
Q

Which enzyme catalyses the reversible reaction between glucose-6-phosphate and glucose-1-phosphate?

A

Phosphoglucomutase

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10
Q

Which enzyme/s catalyse the following reaction:

Glycogen + UDP-glucose -> glycogen + UDP

A

Glycogen synthase
Or
Branching enzyme

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11
Q

What is glycogenolysis?

A

Glycogen degradation

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12
Q

Which enzyme catalyses the following reaction:

Glycogen (n residues) + Pi -> glucose-1-phosphate + glycogen (n-1 residues)

A

Glycogen phosphorylase
OR
De-branching enzyme

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13
Q

True or false: glycogenolysis is a simple reversal of glycogenesis

A

FALSE - different enzymes allow inhibition of one pathway and stimulation of another

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14
Q

How is glucose-6-phosphate used in muscle?

A

Used in glycolysis for energy production

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15
Q

How is glucose-6-phosphate used in the liver?

A

Converted to glucose which is released into the blood for use by other tissues

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16
Q

True or false: liver glycogen is a buffer of blood glucose levels

A

TRUE

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17
Q

Which enzyme does muscle lack?

A

Glucose-6-phosphatase

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18
Q

What is the rate limiting enzyme for glycogen synthesis?

A

Glycogen synthase

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19
Q

What is the rate limiting enzyme for glycogen degradation?

A

Glycogen phosphorylase

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20
Q

What effect does glucagon and adrenaline have on:

1) glycogen synthase
2) glycogen phosphorylase

A

1) decreases enzyme activity

2) increases enzyme activity

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21
Q

What effect does insulin have on:

1) glycogen synthase
2) glycogen phosphorylase

A

1) increases enzyme activity

2) decreases enzyme activity

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22
Q

True or false: glucagon has no effect in the muscle

A

TRUE - no glucagon receptors in muscle

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23
Q

What is an allosteric activator of muscle glycogen phosphorylase but not of the liver form of the enzyme?

A

AMP

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24
Q

What can diminished glycogen stores lead to?

A

Hypoglycaemia and poor exercise tolerance

25
Q

What is von Gierke’s disease?

A

Glucose-6-phosphatase deficiency

26
Q

What happens to the liver in von Gierke’s disease?

A

Hepatomegaly

27
Q

What is McArdle disease?

A

Muscle glycogen phosphorylase deficiency

28
Q

Where does gluconeogenesis occur?

A

In liver and to lesser extent in kidney cortex

29
Q

What are the three major precursors for gluconeogenesis?

A

1) lactate
2) glycerol
3) amino acids (mainly alanine)

30
Q

Why is there no net synthesis of glucose from acetyl-CoA?

A

Acetyl-CoA cannot be converted into pyruvate because the pyruvate dehydrogenase reaction is irreversible

31
Q

Which enzyme converts glucose-6-phosphate to glucose in gluconeogenesis?

A

Glucose-6-phosphatase

32
Q

Which enzyme converts fructose 1,6-bisphosphate to fructose 6-phosphate in gluconeogenesis?

A

Fructose 1,6-bisphosphatase

33
Q

Which enzyme converts oxaloacetate to phosphoenolpyruvate in gluconeogenesis?

A

PEPCK

34
Q

Which two key enzymes are regulated by hormones in response to starvation/fasting, prolonged exercise and stress?

A

Fructose 1,6-bisphosphatase

PEPCK

35
Q

What effect does glucagon and cortisol have on:

1) PEPCK
2) Fructose 1,6-bisphosphatase
3) gluconeogenesis

A

1) increases amount
2) increases amount and activity
3) stimulates

36
Q

What effect does insulin have on:

1) PEPCK
2) Fructose 1,6-bisphosphatase
3) gluconeogenesis

A

1) decreases amount
2) decreases amount and activity
3) inhibits

37
Q

Which receptor does insulin act through?

A

Tyrosine kinase receptor

38
Q

Which receptor does glucagon act through?

A

GPCR

39
Q

Which receptor does cortisol act through?

A

Steroid hormone nuclear receptor

40
Q

How many hours after feeding does gluconeogenesis occur?

A

8-10 hours

41
Q

What is excess energy intake converted to for storage?

A

Triacylglycerol (TAG)

42
Q

True or false: TAGs are hydrophilic and stored in hydrous form in adipose tissue

A

FALSE - hydrophobic so stored in anhydrous form

43
Q

True or false: TAG has an energy content that is twice that of carbohydrate or protein

A

TRUE

44
Q

When is TAG utilised?

A

Prolonged exercise
Stress
Starvation
During pregnancy

45
Q

Why does fatty acid oxidation not occur in the brain?

A

Fatty acids don’t easily pass blood-brain barrier

46
Q

Where does lipogenesis occur?

A

Mainly in liver

47
Q

Which two molecules does lipogenesis require?

A

ATP

NADPH

48
Q

What is the key regulatory enzyme in liver lipogenesis?

A

Acetyl-CoA carboxylase

49
Q

Describe the steps involved in lipogenesis (50

A

1) glucose -> pyruvate (glycolysis)
2) pyruvate enters mitochondria and forms acetyl-CoA and oxaloacetate which condense to form citrate
3) citrate -> cytoplasm and cleaved back to acetyl-CoA and oxaloacetate
4) acetyl-CoA carboxylate produces malonyl-CoA from acetyl-CoA
5) fatty acid synthase complex builds fatty acids by addition of 2 carbon units from malonyl-CoA

50
Q

What does insulin and citrate do to acetyl-CoA carboxylase?

A

Increases activity

51
Q

What does glucagon/adrenaline and AMP do to acetyl-CoA activity?

A

Decreases activity

52
Q

Where does fatty acid oxidation occur?

A

Mitochondria

53
Q

Where does fatty acid synthesis occur?

A

Cytoplasm

54
Q

True or false: fatty acid oxidation is reductive

A

FALSE - oxidative, fatty acid synthesis is reductive

55
Q

What is the term given to fat mobilisation?

A

Lipolysis

56
Q

What do glucagon and adrenaline do to hormone sensitive lipase (HSL)?

A

Lead to phosphorylation and activates HSL

57
Q

What does insulin do to hormone sensitive lipase (HSL)?

A

Leads to de-phosphorylation and inhibits HSL

58
Q

Which protein transports fatty acids to muscle and other tissues?

A

Albumin

Semester 2-MEH (21 decks)

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