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Fundamentals > Lipids > Flashcards

Lipids Flashcards

1
Q

What is a lipid?(2)

A

An organic compound

That is readily soluble in non polar solvent but not in polar solvent

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2
Q

What are the forms of fatty acids in the body?(5)

A 
FFAs
TAGs
Cholesterol esters
Phospholipids 
Glycolipids
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3
Q

What is a fatty acid?

A

A long hydrocarbon chain with a terminal carboxyl group

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4
Q

What is energy from dietary lipids mainly dependant on?

A

Chain length

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5
Q

How many double bonds does saturated fatty acid have?

A

0

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6
Q

How many double bonds does monounsaturated fatty acid have?

A

1

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7
Q

Short chain fatty acids (4)

A

Less than 8 carbons
Water soluble
Mainly found in products containing ruminant milk
Don’t become part of body lipid pool

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8
Q

Medium chain fatty acids (4)

A

8-14 carbons
Arise during synthesis of LCFA
Found in coconut milk and milk fat
Rarely incorporated into body lipid pool

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9
Q

Long chain fatty acids (2)

A

Greater than 14 carbons

Main constituent of dietary fat

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10
Q

Where does fatty acid synthesis occur?

A

Cytosol

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11
Q

Which compound does fatty acid synthesis require?

A

Acetyl CoA

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12
Q

Explain C18:2 cis 9, 12 (3)

A

18 carbons

2 double bonds at carbon 9 and 12 from the carboxyl end

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13
Q

Explain C18:2 n-6 (3)

A

18 carbons

2 double bonds at carbon 6 counting from the methyl end

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14
Q

Which pathway does 6-desaturase prefer and why?

A

N-3

To ensure essential fatty acids are produced

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15
Q

Explain lipid re-esterification during absorption process (4)

A

2-MAGs and FFAs enter enterocytes
It is the converted to DAG by adding a fatty acid and removing CoA
DAG is then converted toTAG

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16
Q

The common saturated fat (2)

A

Palmatic acid C16:0

Stearic acid C18:0

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17
Q

Common monounsaturated fat

A

Oleic acid C18:1

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18
Q

Common polyunsaturated fats (2)

A

Linoleic acid C18:2

DHA C22:6

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19
Q

What form is most body fat stored as?

A

TAG

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20
Q

Fatty acid synthesis in the cytosol (5)

A 
Acetyl CoA C2:0
Malonyl CoA C3:0
Palmitic acid C16:0
Stearic acid C18:0
Oleic acid C18:1
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20
Q

Enzymes of fatty acid synthesis in the cytosol (4)

A

Acetyl CoA carboxylase
Fatty acid synthase
Elongase
9-desaturase

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20
Q

What is the importance of the enzymes 6-desaturase?(2)

A

All fatty acid pathways use this enzyme

It’s the key enzyme that determines which PUFAs are produced

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20
Q

What is the average fat intake in the western diet?(2)

A

50-100g per day

35-40% total energy

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21
Q

Why are dietary lipids important?(8)

A 
Provide energy  
Cell signalling 
Food texture
Food flavour
Hormone precursors 
Supply fat soluble vitamins 
Supply essential fatty acids 
Insulation
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23
Q

Explain the gastric stage of TAG digestion (5)

A 
Lingual lipase secreted from glands under tongues 
Travels with food to stomach 
Penetrates milk fat globules 
Hydrolyses fatty acids 
Chyme is released into the duodenum
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24
Q

Duodenal phase of digestion (6)

A

TAG (in chyme) is released into the duodenum
Chyme stimulates the release of CCK
Bile acids are secreted from the gall bladder
Pancreatic lipase are released
Lipid droplets are then coated in bile salts
Which forms micelles

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25
Q

What does pancreatic lipase do?(3)

A

Binds to micelles
Hydrolyses TAG in the presence of Ca2+
Produces two fatty acids and 2-MAG

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26
Q

How are fats solubilised?(2)

A

By associating with bile salts and forming micelles

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27
Q

Why must fats be emulsified?(3)

A

To increase accessibility of fats to digestive enzymes
This is because fats are hydrophobic
And digestive enzymes are hydrophilic

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28
Q

What happens after TAG esterification during absorption process? (4)

A

They are packed into chylomicrons
So they are able to be transported
Chylomicrons are then released into the lymphatic system
The chylomicron then passes into the blood stream

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29
Q

Chylomicron metabolism (4)

A

Interacts with lipoprotein lipase
TAG in chylomicrons is hydrolysed to release FFAs

FFAs are either oxidised for energy in muscle
Or re-esterified to form TAG for storage in adipose tissue

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30
Q

What happens after most of the TAG in the chylomicron is hydrolysed?(2)

A

It becomes a chylomicron remnant

It is then removed from the blood by the liver

31
Q

What is the function of plasma lipoproteins (2)

A

Transport lipids from the site of production or absorption to the site of utilisation and storage

32
Q

Role of LDL

A

Transport cholesterol from liver to body tissues

33
Q

Role of VLDL

A

Transport newly synthesised TAG from liver to peripheral tissues

34
Q

Role of HDL

A

Transport cholesterol from tissues to liver

35
Q

What are the essential fatty acids obtained by and their formula (2)

A

Linoleic acid C18:2, n-6

a-linolenic acid C18:3, n-3

36
Q

Potential consequences of essential fatty acid deficiency (2)

A

Increase permeability to water and small molecules

Reduced efficiency of oxidative phosphorylation in mitochondria

37
Q

Ketone can be used by tissue that can’t use ____

A

FAs

38
Q

Name some organs that can’t use fatty acids (3)

A

Brain
Kidney medulla
Eye

39
Q

Classes of lipids (4)

A

Simple
Complex
Derived
Miscellaneous

40
Q

Examples of simple lipids (3)

A

FAs esterified with glycerol
TAG
Waxes

41
Q

Example of complex lipids (3)

A

Phospholipids
Glycolipids
Lipoproteins

42
Q

Examples of derived lipids (3)

A

Saturated fats
Monounsaturated fats
Polyunsaturated fats

43
Q

Major biological roles of FAs (4)

A

Energy storage
Protection
Essential components of biological membranes
Precursors of bio active molecules

44
Q

Sources of palmitic acid (3)

A

Meat
Dairy products
Palm oil

45
Q

Sources of oleic acid (3)

A

Meat
Dairy products
Olive oil

46
Q

Stearic acid sources (3)

A

Animal fats
Vegetable fats
Cocoa butter

47
Q

Linoleic acid sources (2)

A

Sunflower oil

Corn oil

48
Q

DHA sources

A

Oily fish

49
Q

What are bile salts?(3)

A

Hydroxylated steroids derived from cholesterol
Conjugated to an AA side chain
Amphipathic

50
Q

What is FA transport across the membrane dependent on?

A

Inward diffusion gradient

51
Q

What happens to bile acids during absorption (4)

A

Pass through to ileum
Absorbed and recirculated in the portal vein
To the liver
Re-enter the duodenum

52
Q

Where do LCFAs originate from?(3)

A

Diet
Synthesis of acetyl CoA
Elongation of SCFA

53
Q

Stages of TAG digestion (3)

A

Gastric
Duodenal
Ilial

54
Q

Production of PUFAs (3)

A

Derived from MUFA
Double bond inserted into LCFAs
Uses desaturase enzyme

55
Q

What is co-lipase?(3)

A

Co-enzyme secreted by pancreas
And absorbed on to surface of oil droplet
Acts as an anchor for pancreatic lipase at the oil/water interphase

56
Q

Where does the majority of fat absorption occur?

A

Jejunum

57
Q

When does fat absorption occur?

A

When the micelles come into contact with the microvillus membrane of the enterocytes

58
Q

Fat absorption process (3)

A

Lipids absorbed but not bile salts
Lipids transferred from micelles to enterocyte
Facilitated by FA binding proteins

59
Q

Why are some fatty acids essential?(2)

A

Mammals lack the enzymes to insert double bonds beyond C9 in a chain
Between existing bond and carboxyl group

60
Q

N-9 pathway (6) C18:1 - C24:4

A 
Oleic acid C18:1
C18:2
C20:2
C20:3
C22:3
C24:4
61
Q

N-6 pathway (6) C18:2 - C22:5

A 
Linoleic acid C18:2
a-linolenic acid C18:3
C20:3
Arachidonic acid C20:4
C22:4
Docosapentanoic acid C22:5
62
Q

N-3 pathway (6) C18:3 - C22:6

A 
a-linolenic acid C18:3
C18:4
C20:4
EPA C20:5
C22:5
DHA C22:6
63
Q

Which essential fatty acid is a component of the retina?

A

DHA

64
Q

Roles of eicosanoids (3)

A

Mediate variety of cellular functions
Local hormones
Modulate inflammatory response

65
Q

Which cellular functions do eicosanoids mediate?(2)

A 
Smooth muscle contraction 
Platelet aggregation (Blood clotting)
66
Q

Role of eicosanoids as local hormones (2)

A

Paracrines

Autocrines

67
Q

How do eicosanoids modulate inflammatory responses?(3)

A

Regulate constriction and dilation of blood vessels
Prostacyclins inhibit platelet aggregation
Thromboxanes stimulate platelet aggregation

68
Q

What are eicosanoids?

A

Derivatives of omega 3 and omega 6

69
Q

Which type of fatty acid produces more potent eicosanoids?

A

Omega 6

70
Q

Mechanisms by which omega 3 reduces CVD risk?(5)

A 
Reduced susceptibility of heart and ventricular arrhythmia 
Reduces adhesion molecule expression
Anti-inflammatory effect 
Promotes endothelial relaxation
Mildly hypotensive
71
Q

What are conjugated linoleic acids?

A

Linoleic acids which have double bonds next to each other

72
Q

How are CLAs produced?(3)

A

Rumen bacteria tend to saturate double bonds in fatty acids
CLAs are produced as intermediates of this process
Some of the intermediates escape and enter tissues

73
Q

Potential health benefits of CLAs (5)

A 
Anti-carcinogenic 
Modulation of body composition 
Anti-diabetic 
Immunity enhancement 
Improved bone mineralisation
74
Q

How much energy does a gram of fat produce?

A

39.1kJ

75
Q

What are the two predominant CLAs?

A

Cis-9, trans 11

Trans 10, cis 11

76
Q

What are micelles?(3)

A

Spherical aggregates of amphipathic molecules
Consists of a hydrophobic core
And hydrophilic surface

Fundamentals (17 decks)

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