Energy Production- Lipids Flashcards Preview

Z OLD ESA 1- Metabolism > Energy Production- Lipids > Flashcards

Flashcards in Energy Production- Lipids Deck (131):
1

Are lipids structurally similar or diverse?

Diverse

2

Are lipids generally hydrophilic or hydrophobic?

Hydrophobic

3

What is the result of lipids generally being hydrophobic?

They’re generally insoluble in water

4

What elements to most lipids contain?

C, H and O only

5

What elements do some lipids contain?

Phospholipids contain P and N

6

Are lipids more or less reduced than carbohydrates?

More

7

What is the result of lipids being more reduced than carbohydrates?

#NAME?

8

What are the 3 classes of lipids?

- Fatty acid derivatives
- Hydroxy-methyl-glutaric acid derivates 
- Vitamins

9

What are the 4 types of fatty acid derivatives?

#NAME?

10

What are fatty acids used for?

Fuel molecules

11

What are triglycerides used for?

#NAME?

12

What are phospholipids used for?

Components of membranes and plasma lipoproteins

13

What are eicosanoids used for?

Local mediators

14

What do local mediators do?

Signal between cells

15

What is the advantage of having local mediators?

They produce a coordinated response

16

What are the 4 types of hydroxy-methyl-glutatic acid derivatives?

#NAME?

17

What are ketone bodies?

Water soluble fuel molecules

18

What are ketone bodies derived from?

Fats

19

What is cholesterol used for?

- Membranes 
- Steroid hormone synthesis

20

What are cholesterol esters used for?

Cholesterol storage

21

What are bile acids and salts used for?

Lipid digestion

22

Can the body make vitamins?

No

23

What are triacylglycerols (TAGs) composed of?

- Glycerol backbone 
- Fatty acid side chain

24

What is the glycerol backbone in TAGs?

3C sugar derived from glycolysis

25

What does the fact that the glycerol backbone comes from glycolysis mean?

Fatty acid synthesis requires glycolysis

26

Why is it said that the fatty acid side chains are highly reduced?

There are 2 H’s on every atom

27

What is the process of producing TAGs from glycerol and fatty acids called?

Esterification

28

What is the process of producing glycerol and fatty acids from TAGs called?

Lipolysis

29

What must be done due to the fact that TAGs are hydrophobic?

They must be stored in anhydrous form

30

What tissues are TAGs stored in?

Specialised tissue- adipose

31

When are TAGs utilised?

#NAME?

32

How is storage and mobilisation of TAGs controlled?

Hormones

33

What are triglycerides broken down to in the GI tract?

#NAME?

34

Can glycerol and fatty acids be transported in the blood?

- Glycerol can 
- Fatty acids can't

35

How are fatty acids transported in the blood?

On chylomicrons

36

Where does glycerol end up?

Liver

37

Where do chylomicrons take fatty acids?

Adipose tissue

38

What happens when the muscles demand fuel?

Adipose is broken down to release fatty acids, which are carried in the blood to muscles

39

Where does stage 1 of dietary triacylglycerol metabolism occur?

In the GI tract- extracellular

40

What does stage 1 of dietary TAG metabolism occur due to?

Lipases

41

What releases the lipases responsible for stage 1 of TAG metabolism?

Pancreas

42

What do the lipases do in stage 1 of TAG metabolism?

Hydrolyse lipids in the small intestine into fatty acids and glycerol

43

What happens once the lipids have been hydrolysed in the small intestine?

They are recombined in the small intestine and transported as TAG by lipoproteins (chylomicrons)

44

Where do chylomicrons transport TAG’s to?

Adipose tissue and consumer tissue

45

What happens to TAGs in adipose tissue?

It is stored as TAG until fat mobilisation

46

What stimulates fat mobilisation?

Glucagon / adrenaline

47

What inhibits fat mobilisation?

Insulin

48

What enzyme is responsible for fat mobilisation?

Hormone-sensitive lipase

49

What carries mobilised fat from adipose tissue to consumer tissues?

FA-albumin

50

Why is FA-albumin needed to carry mobilised fat?

Because fat is insoluble, therefore can’t go around on it’s own

51

What happens to fats at consumer tissues?

Fatty acids are oxidised to produce energy

52

Where can fatty acid oxidation not occur?

- Tissues without mitochondria, e.g. RBCs 
- Brain

53

Why can’t fatty acids be oxidised to produce energy in tissues without mitochondria?

They are highly reduced, so produce lots of reducing equivalents, which needs mitochondria

54

Why can’t fatty acids be oxidised to produce energy in the brain?

Fatty acids don’t easily pass through the blood-brain barrier

55

What happens to fatty acids in the GI tract?

They are converted back to triglycerides

56

How are fatty acids packaged?

Into lipoprotein particles- chylomicrons

57

How are packaged fatty acids released into circulation?

Via lymphatics

58

What does low extracellular [glucose] result in?

Fatty acid release as an alternative fuel

59

Why does low extracellular [glucose] lead to fatty acid release as an alternative fuel?

If [glucose] falls, [glycerol-1-P] also falls, so substrate not available for resynthesis, leading to fatty acid build up

60

What is the general formula of fatty acids?

CH 3 (CH 2 ) n COOH
where n=14-18

61

Are fatty acids saturated or unsaturated?

Can be either

62

What is meant by fatty acids being amphipathic?

They contain both hydrophilic and hydrophobic groups

63

Why are certain polyunsaturated fatty acids essential?

Mammals cannot introduce a double bond beyond C9

64

Where does stage 2 of FA metabolism occur?

Mitochondria

65

Where is the FA activated?

Outside of mitochondrion, in the cytoplasm

66

How is a FA activated?

By linking of CoA, via a high energy bond

67

What enzyme is used to activate FA’s?

Fatty acid CoA synthase

68

Give the equation for the activation of fatty acids

Fatty acid + ATP + CoA → fatty acid~CoA + AMP +2Pi

69

What is 2Pi

Pyruphosphate- 2 phosphates together

70

Is 2Pi stable or unstable?

Very unstable

71

What is the result of 2Pi being very unstable?

It hydrolyses spontaneously, pushing the reaction in the forward direction

72

How are activated fatty acids transported across inner mitochondrial membrane?

Using carnitine shuttle

73

What happens to FA during stage 2 of FA metabolism?

They cycle through a sequence of oxidative reactions, with C 2 removed each cycle

74

Give the equation for the reaction that occurs at each cycle of stage 2 of FA metabolism?

C n + FAD + H 2 O + NAD +  → C n-2 + C 2 + FADH 2 + NADH + H +

75

What does the carnitine shuttle do?

Transports fatty acyl~CoA across the mitochondrial membrane

76

How does the carnitine shuttle work?

- In the intermembrane space, carnitine is converted to acyl carnitine by action of the enzyme of CAT1. This reaction also converts acyl~CoA to CoA
- The acyl carnitine can be transported through the inner mitochondrial membrane by the carnitine shuttle transporter 
- In the matrix, acyl carnitine is converted to carnitine by the action of CAT2. This reaction also converts CoA to acyl~CoA- there is now acyl~CoA inside the matrix .
- The carnitine produced can be transported back out to  the intermembrane space by the carnitine shuttle transporter

77

What is the result of the carnitine shuttle be regulated?

It controls the rate of FA oxidation

78

What inhibits the carnitine shuttle?

Malonyl~CoA

79

What is malonyl~CoA?

Short, activated fatty acid that is a precursor to fat biosynthesis

80

What can happen if there are defects in the transport system?

Won’t be able to switch to fatty acid metabolism, because can’t get across mitochondrial membrane

81

What are the symptoms of defects in the carnitine transport system?

#NAME?

82

What is fatty acid catabolism also known as?

ß-oxidation

83

Give the equation for ß-oxidation

C n  + FAD + H 2 O + NAD + + CoA→ C n-2  + acetyl~CoA   + FADH 2  + NADH + H +

84

What are all intermediates linked to in ß-oxidation?

CoA

85

Is more energy derived from glucose or FA metabolism?

FA

86

Where is glycerol metabolised?

In the liver

87

How does glycerol get to the liver?

It is transported in the blood

88

Describe the metabolism of glycerol

- Glycerol converted to glycerol phosphate by the action of glycerol kinase. This requires ATP
- Glycerol phosphate can be used in triacylglycerol synthesis, or converted into DHAP (which also converts NAD + to NADH)
- DHAP can then be used in glycolysis

89

What is the main convergence point for catabolic pathways?

Acetyl-CoA

90

What does acetyl-CoA consist of?

CH 3 CO group linked to CoA

91

How is the CH 3 CO group linked to CoA?

Via a S atom

92

What is the significance of acetyl-CoA being linked by a S atom?

High energy of hydrolysis, therefore is an energy storing bond

93

What vitamin does CoA contain?

B

94

What is the significance of CoA containing vit B?

The body can’t produce it

95

What is the function of acetyl~CoA?

It’s an important intermediate in both catabolic and anabolic pathways

96

What can acetyl~CoA be converted into?

- Fatty acids
- CO 2
- Hydroxymethylglutaric acid (HMG)

97

What can fatty acids be converted into?

#NAME?

98

What can HMG be converted into?

#NAME?

99

How many ketone bodies are produced in the body?

3

100

What are the 3 ketone bodies produced in the body?

#NAME?

101

Effectively, what is acetoacetate?

2 acetate molecules linked together

102

Where is acetoacetate found?

Liver

103

What produces acetone?

Spontaneous (non-enzymatic) decarboxylation of acetoacetate

104

Where is ß-hydroxybutayrate found?

In the liver

105

What is the normal plasma ketone body concentration?

106

What is it called when a patient has a plasma ketone concentration of 2-10mM?

Physiological ketosis

107

When may physiological ketosis occur?

Starvation conditions

108

What is it called when a patient has a plasma ketone concentration of >10mM?

Pathological ketosis

109

When may pathological ketosis occur?

Untreated type 2 diabetes

110

What synthesises ketone bodies?

Liver mitochondria

111

Describe the synthesis of ketone bodies

- Acetyl~CoA converted into HMG~CoA by action of synthase
- HMG~CoA can be converted into mevalonate by action of HMG-CoA reducatase (which is consequently converted into cholesterol), or acetoacetate by action of lyase. 
- Acetoacetate converted to acetone by spontaneous breakdown, or ß-hydroxybutyrate

112

How can HMG-CoA be used as a site of action clinically?

For statin drugs- if inhibited, it can reduced cholesterol levels in patients

113

How is ketone body production controlled in the liver?

The acetyl-CoA can be diverted into the TCA cycle, which reduces substrate availability for ketone body production

114

What enzymes are involved in the regulation of ketone body production in the liver?

- Isocitrate dehydrogenase 
- α-ketoglutarate dehydrogenase

115

How does isocitrate dehydrogenase and α-ketoglutarate dehydrogenase regulate ketone body production in the liver?

- These enzymes are inhibited by low NAD +  substrate availability and NADH product inhibition. 
- If they are inhibited, build up of product, meaning less acetyl-CoA diverted into TCA cycle, so more ketone body production

116

Describe the metabolism of ketone bodies

- Acetoacetate and ß-hydroxybutyrate in the liver can be transported in the blood to the muscle 
- In the muscle, ß-hydroxybutyrate is converted into acetoacetate (which also causes conversion of NAD + to NADH)
- Acetoacetate + succinyl CoA (in the TCA)  → acetoacetate~CoA+ succinate (in the TCA)  - this reaction keeps the TCA cycle going, which produces ATP 
- The acetoacetate~CoA is converted into acetyl~CoA, which feeds into the TCA cycle at citrate

117

What happens when acetoacetate is carried in the blood?

Some is lost as acetate in the bloodstream

118

What happens when ß-hydroxybutyrate is carried in the blood?

It also carries hydrogen

119

What hormone ratio regulates ketone body synthesis?

Insulin:glucagon

120

In what insulin:glucagon ratio are ketone bodies synthesised?

When insulin is low, therefore glucagon is high

121

In what conditions would insulin be low and glucagon high?

#NAME?

122

What happens when insulin is high and glucagon is low?

Lyase (the enzyme that produces ketone bodies is inhibited), and reductase is activated, leading to cholesterol synthesis

123

What is the advantage of ketone bodies in starvation conditions?

They spare glucose

124

Why is advantageous for ketone bodies to spare glucose?

The body needs to maintain circulating glucose to supply the brain, RBC etc

125

Are ketone bodies hydrophilic or hydrophobic?

Hydrophilic

126

What happens when ketone bodies rise above the renal threshold?

They are excreted in urine

127

What is it called when ketone bodies are excreted in urine?

Ketouria

128

What condition occurs when ketone body concentrations get to high?

Ketoacidosis

129

What is ketoacidosis?

Acidification of the circulation

130

Why does ketoacidosis occur?

Because acetoacetate and ß-hydroxybutyrate are relatively strong organic acids

131

Why can ketoacidosis sometimes be detected on the breath?

Because the volatile acetone may be excreted via the lungs