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Structure + Function 1 > lipids > Flashcards

lipids Flashcards

1
Q

Functions of lipids?

A

Store energy

Water repellent

Buoyancy control and acoustics in marine animals

Cofactors for enzymes

Protect organs

Insulation from environment

Pigments

Digestion

Membrane structure

Signalling molecules

Antioxidants

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2
Q

What is a FFA?

A

Free fatty acid

Not a component of another lipid

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3
Q

Describe fatty acid structure

A

Fatty -hydrocarbon chain

Acid - carboxyl group

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4
Q

How long can the fatty acid hydrocarbon chain be?

A

2-24 carbons

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5
Q

Why is the hydrocarbon chain hydrophobic?

A

can’t form hydrogen bonds with H2O

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6
Q

What are SFAs?

A

Saturated fatty acids

no double bonds in hydrocarbon chain

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7
Q

What are MUFAs?

A

Mono unsaturated fatty acids

Have 1 C=C in hydrocarbon chain

Usually has a kink

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8
Q

What are PUFAs?

A

Polyunsaturated fatty acids

Multiple C=C in hydrocarbon chain

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9
Q

How does the number of C=C in the hydrocarbon chain affect fatty acid boiling point?

A

More C=C lowers the boiling point

e.g
olive oil - oleic acid - PUFA - liquid at room temp

butter - mostly SFAs - solid at room temp

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10
Q

Naming fatty acids, which is carbon 1?

A

carbon of carboxyl group

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11
Q

What is the second carbon in fatty acids called?

A

α carbon or carbon 2

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12
Q

If the name of a fatty acid has 14:3 included, what does this mean?

A

14 - number of carbons

3 - number of C=C

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13
Q

What is the Δ used for when naming fatty acids?

A

Shows position of double bond

E.g Δ 5,9 shows there are double bonds on carbons 5 and 9

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14
Q

What does it mean if a double bond is:

Cis

Trans

A

Cis - H atoms on same side of double bond

Trans - H atoms on opposite sides of double bond

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15
Q

All natural fatty acids are cis or trans?

A

cis

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16
Q

What is the last carbon in the hydrocarbon chain called?

A

Omega ( ω ) carbon

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17
Q

What does it mean if a FA is an:

omega 3 FA

omega 6 FA

A

omega 3 - first C=C is on the 3rd carbon counting from the ω carbon

omega 6 - first C=C is on the 6th carbon counting from the ω carbon

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18
Q

Omega-3 fatty acids are considered…

A

Anti-inflammatory

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19
Q

Omega-6 fatty acids are considered…

A

Pro-inflammatory

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20
Q

Example of an omega-6 fatty acid?

A

Arachidonic acid

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21
Q

example of an omega-3 fatty acid?

A

Eicosapentaenoic acid (EPA)

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22
Q

3 derivatives of arachidonic acid and their functions

A

Prostaglandins
fever, renal blood flow, mucosal protection, inflammation

Thromboxanes
formation of blood clots

Leukotrienes
inflammation, smooth muscle contraction in lungs

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23
Q

What is arachidonic acid made from?

what enzyme does it use?

A

Cell membrane phospholipids

uses phospholipase enzyme

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24
Q

what are the 3 arachidonic acid derivates?

A
  • leukotrienes
  • prostoglandins
  • thromboxane and prostaglandins
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25
Q

what pathway is leukotrienes produced by?

A

lipoxygenase pathway

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26
Q

what pathway are prostaglandins and thromboxane produced by?

A

cyclooxygenase pathway

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27
Q

what is needed to produce (prostaglandins and thromboxane)

A

cox-1

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28
Q

what is needed to produce just prostaglandin

A

cox-2

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29
Q

is cox 1 physiological or inducible?

A

physiological

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30
Q

is cox 2 physiological or inducible?

A

inducible

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31
Q

What will inhibit the production of arachidonic acid?

A

Corticosteroids

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32
Q

What will inhibit the production of both thromboxane and prostaglandins?

A

NSAIDS - non-steroidal anti-inflammatory drugs

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33
Q

Examples of NSAIDS?

A

Ibuprofen

Phenylbutazone

Diclofenac

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34
Q

Describe COX-2 preferential NSAIDs and examples of them

A

Affect COX-2 more than COX-1

Meloxicam
Carprofen

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35
Q

Example of COX-2 specific NSAID

A

coxibs

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36
Q

Why shouldn’t you use steroids and NSAIDs together?

A

Steroids reduces arachidonic acid formation

no need for NSAIDs too

more side effects

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37
Q

What are TAGs?

A

Triacylglycerols/ triglycerides

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38
Q

Describe the structure of TAGs

A
  • 3 fatty acids
  • can be different
  • 1 glycerol
  • Fatty acids joined to glycerol by ester bonds ( C=O-O-C) : each of the 3 OH groups in glycerol forms an ester bond with the carboxyl group of a fatty acid
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39
Q

How are the ester bonds in TAGs broken?

A

hydrolysed by lipases or esterases

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40
Q

Can TAGs cross the cell membrane?

A

no

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41
Q

What are the main lipid components of dietary fats?

A

TAGs

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42
Q

how are TAGs digested

A
  • TAGs are digested into FA and monoacylglycerol components in the small intestine.
  • Re-constituted into TAGs within enterocytes.
  • Packaged in the ER of enterocytes into
    chylomicrons.
  • Enter the lymphatic system via the lacteal where they join lymph fluid to become chyle fluid.
    Chyle returns to vascular system through venous return and then supplies tissues with TAGs.
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43
Q

what are chylomicrons?

A
  • lipoproteins: composed of phospholipids and
    apolipoproteins
  • transport fat from small intestine (where absorbed) to liver and adipose tissues
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44
Q

Where are lacteals found?

A

In small intestine villi

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45
Q

What is chyle fluid?

A

Lymph fluid containing many chylomicrons

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46
Q

When are fatty acids used for energy?

A

Fasting/starvation

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47
Q

Where are TAGs stored?

A

adipocytes

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48
Q

What is excess glucose converted to?

A

Fatty acids

Glycerol

stored in apodicytes

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49
Q

Is storage of TAGs in apodicytes short or long term?

A

long term

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50
Q

When would there be an excess glucose?

A

Energy requirements met

Glycogen store full

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51
Q

When does lipogenesis occur?

A

Glucose surplus + glycogen store full

Transported to liver in blood

Converted to fatty acids and glycerol in the liver

52
Q

Describe the pathway of lipogenesis

A

Glucose synthesises glycerol

Glycolysis of glucose produces pyruvate

Pyruvate forms acetyl coA

Provides 2C at a time

NADPH needed to form fatty acids from acetyl coA

53
Q

What are lipoproteins transported from hepatocytes as?

A

VLDL - very low density lipoprotien

54
Q

Describe lipoproteins

A

Same structure as chylomicrons

Transport TAGs and cholesterol

Higher cholesterol than chylomicrons

Named according to density

less cholesterol = higher density

VLDL, IDL, LDL, HDL

Transport fats around the body

55
Q

How are fatty acids freed from lipoproteins?

A

Lipoprotein lipases

56
Q

What is lipolysis?

A

Breakdown of stored TAGs in apodicytes to fatty acids and glycerol

57
Q

What induces lipolysis?

A

Several hormones:

glucagon

cortisol

adrenaline

58
Q

When does lipolysis occur?

A

After 24 hour fasting

Endurance exercise - ‘going through the wall’ switch from glucose metabolism to lipid metabolism

59
Q

Why can FFAs exist in the blood freely?

How do they usually travel in the blood?

A

Have carboxyl group - hydrophilic

Bound to albumin

60
Q

What can use FFAs freely?

What can’t and why?

A

Muscle + the liver

Brain:
FA too large to cross blood brain barrier

61
Q

How are fatty acids metabolised?

A

Β-oxidation

In mitochondria

62
Q

Can fatty acids cross the mitochondrial double membrane?

A

No

Transported in by carnitine shuttle

63
Q

Where can large FA be oxidised?

A

Peroxisomes

64
Q

Steps of the carnitine shuttle

A
  1. Fatty acid binds to coA ⇒ fatty acyl coA via fatty acyl CoA synthase (FACS) in cytoplasm
  2. CoA exchanged for carnitine ⇒ acyl carnitine using CPT 1 (carnitine palmitoyltransferase I)
  3. Acyl carnitine translocated by facilitated diffusion using an unbound carnitine via CAT (Acylcarnitine translocate)
  4. Carnitine of the acyl carnitine exhanged for coA via CTP 2 ( carnitine palmotoyltransferase II)⇒ fatty acyl coA reformed - B-oxidation can now occur
64
Q

Steps of the carnitine shuttle

A
  1. Fatty acid binds to coA ⇒ fatty acyl coA
  2. CoA exchanged for carnitine ⇒ acyl carnitine
  3. Acyl carnitine translocated by facilitated diffusion using an unbound carnitine
  4. Carnitine of the acyl carnitine exhanged for coA ⇒ fatty acyl coA reformed - B-oxidation can now occur
65
Q

Describe B-oxidation

A

2 carbons removed from fatty acid chain at a time

produces acetyl coA

produces NADH and FADH2

Acetyl coA then used for krebs/TCA cycle

NADH and FADH2 used in oxidative phosphorylation (ETC)

66
Q

What happens when there is excess acetyl coA?

A

Goes into ketogenesis cycle

67
Q

What happens in ketogenesis?

A

Excess acetyl coA converted into ketones

68
Q

What can be smelled on the breath of an animal suffering from ketoacidosis?

A

Acetone - sweet smelling/ pear drops

e.g milk fever, uncontrolled diabetes

69
Q

what can be produced from ketogenesis?

A
  • acetoacetate
  • b- hydroxbutyrate
  • acetone
70
Q

What is pregnancy toxaemia in sheep also known as?

A

twin lamb disease

71
Q

Describe twin lamb disease

A
  • affects ewes in late gestation
  • often those with more than one lamb
  • inadequate nutrition during late gestation/ anorexia
  • foetal glucose demands can’t be met by the ewe/gluconeogenesis
  • adipose stores are mobilised and fatty acids are b-oxidised
  • excess fatty acid metabolism results in ketone formation and ketoacidosis- pregnancy toxaemia
72
Q

Describe milk fever

A

Bovine toxosis

Usually affects dairy cow in early lactation

Caused by inadequate nutrition in last gestation + early lactation

Glucose requirements for milk production not met by gluconeogenesis

Adipose stores mobilised

B-oxidation of fatty acids

Excess metabolism causes ketone formation

excess acetone= ketoacidosis

73
Q

What are phospholipids also called?

A

Glycerophospholipids

74
Q

Components of phospholipds

A
  • 2 fatty acids
    *usually one saturated, one unsaturated
  • Phosphate group
    *bound to 3’ C of glycerol
  • Glycerol

*Polar head group can vary

75
Q

Why are phospholipid heads hydrophilic?

A

Phosphate group is negatively charged

76
Q

Describe the most common phospholipid in the plasma membrane

A

Phosphoatidylcholine

has choline polar head group

77
Q

Which glycerophospholipid is involved in cell-signalling processes?

A

Phosphoatidylinositol 4,5 -biphosphate

78
Q

Describe cardiolipin

A

Phospholipid

Found in cardiac tissue and mitochondria

Biomarker for apoptosis

Head group is another phospholipid

4 fatty acids in the molecule overall

79
Q

What are sphingolipids? How do they relate and differ to phospholipids (structure)

A

Lipids found in plasma membrane

Both have hydrophilic/phobic parts

Sphingolipids only have one fatty acid

80
Q

Sphingolipid structure

A

Fatty acid linked to sphingosine

no glycerol

Head group attached to sphingosine

head group + sphingosine = sphingoid base

81
Q

Structure of sphingomyelin?

A

Fatty acid

Sphingosine

Phosphocholine head group

82
Q

3 functions of sphingomyelin

A

Myelin sheath surrounding + insulating nerve cell axons

Role in action potential transduction

Involved in apoptosis

83
Q

What are glycosphingolipids?

Example?

A

Sphingolipids with carbohydrate head group

Blood group

diff carb head group = diff blood group

84
Q

What is cholesterol the starting point for?

A

Many sterols

85
Q

Why are sterols very hydrophobic?

A

High carbon content

86
Q

How can you tell a sterol apart from other lipids?

A

Conserved ring structure

4 carbon rings

3 hexagonal

1 pentagonal

87
Q

What is cholesterol needed for?

A

Proper membrane function

Steroid hormone synthesis

88
Q

How do animals obtain cholesterol?

A

Dietary source

Synthesise from acetyl coA

89
Q

2 examples of sex hormones

A

Testosterone

Oestrogen

90
Q

What is cortisol?

Importance?

Excessive amounts can cause?

A

Stress response steroid hormone

Induce gluconeogenesis when starvation

Cushing’s disease

91
Q

Importance of aldosterone?

A

Causes Na retention and K excretion in kidneys

This causes water retention

92
Q

Which disease results in reduced/no production of aldosterone?

What does this cause?

A

Addison’s disease - destroys aldosterone producing cells

Electrolyte imbalance, dehydration, death

93
Q

2 steroid drugs used in practice

A

Prednisone

Prednisolone

94
Q

Steroid hormone found in cabbages?

A

Brassinolide

95
Q

Cholesterol is the starting point for the synthesis of…

A

Bile acids

96
Q

Why are bile acids important?

A

Detergents

Emulsify lipids

allow lipase to break lipid down

Cholesterol homeostasis

too much cholesterol = make more bile acids

97
Q

Describe the path from primary bile acids to secondary to conjugated

A

Primary bile acid dehydoxylated

hydroxyl group removed

Secondary bile acid made

then conjugated by glycine or taurine

Makes conjugated bile acid

now hydrophilic

98
Q

How do bile acids aid in fat digestion?

A

Break fats into smaller droplets/micelles

Allows pancreatic lipases to break lipid down

99
Q

Hydrophobic/philic parts of the bile acid?

A

Phobic- sterol

Philic - conjugated amino acid

100
Q

what are the fat soluble and water soluble vitamins?

A

fat soluble- K A D E
water soluble- B C

101
Q

How is vitamin D3 manufactured?

A

Cholesterol in skin

Presence of sunlight

uv-b radiation

processes in skin, liver, kidney

102
Q

What is vit D3 needed for?

What happens if deficient?

A

Calcium absorption in small intestine

Rickets - bones not developed properly

103
Q

What is retinol?

A

vitamin A

104
Q

Is vitamin A derived from cholesterol?

A

No - doesn’t have 4 ring structure

105
Q

Is retinol hydrophilic or hydrophobic?

A

Hydrophobic

106
Q

What is retinol produced from?

A

B-carotene

found in carrots

Split into 2 identical molecules - retinol

107
Q

How is retinal converted to retinoic acid? What is this important for?

A

11-cis- retinal oxidised

forms retinoic acid

108
Q

Why is vitamin E hydrophobic?

A

Large carbon chain

109
Q

Role of vitamin E

A

antioxidant properties
- the important antioxidant in hydrophobic environments such as within cell membranes
- protects fatty acids within cell membranes from oxidation

110
Q

Differences and similarities of vitamins C and E

A

Similarities - both antioxidant

Diff - vit C is hydrophilic

Vit C works in aqueous environments - not hydrophobic

111
Q

Importance of vitamin K

A

Cofactor in blood coagulation pathway

112
Q

Is vitamin K hydrophobic or hydrophilic?

A

hydrophobic

113
Q

Describe the blood coagulation pathway

A

Vit K is a cofactor for Vit-K dependent carboxylase enzyme

Enzyme adds carboxyl group to glutamate residues in certain clotting factors

makes carboxyglutamate residues

CG residues chelate Ca ions

enables clotting factors to bind to cell membranes and form a clot

114
Q

What happens to vitamin K in the blood coagulation process?

What must be done to maintain balance?

A

oxidised in process so needs to be reduced

115
Q

How does warfarin work?

A

Inhibits enzyme that oxidises reduced Vitamin K

Vitamin K is not active whilst it is reduced

Means that blood cannot clot

116
Q

How can you treat a dog that has eaten rat poison?

A

Make them sick

If late , oversupply with vitamin K

117
Q

Which vitamin is the liver very rich in?

A

Vitamin A

118
Q

3 things vitamin A is needed for

A

Vision

Gene regulation

Appropriate bone turnover

119
Q

Excess of vitamin A causes.. (bones)

A

Excessive breakdown of bone

by osteoclasts

Causes loss of bone from general skeleton

High Ca released from lost bone in skeleton

Circulates and deposits in inappropriate locations

New bone formed in inappropriate locations

120
Q

Why is vitamin A toxic at high doses but vitamin C isn’t?

A

Vit C water soluble - can be excreted

Vit A hydrophobic

needs to be converted to hydrophilic in order to be secreted

Vit A stored in adipose tissue

not accessible to drug metabolism enzymes

121
Q

Structure of waxes

A

Long chain fatty acid

Long chain alcohol

Joined by ester bond

122
Q

Functions of waxes

A

Plankton use as energy store

Waterproofing feathers

Protection + pliability of hair and skin

Beeswax

123
Q

Who makes polyketides?

What do we used them for?

A

Plants and fungi

Drugs

124
Q

Many pigments are ___ - based

A

fat

Structure + Function 1 (18 decks)

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