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Flashcards in Lipids Deck (78):
1

What is a lipid?(2)

An organic compound
That is readily soluble in non polar solvent but not in polar solvent

2

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

FFAs
TAGs
Cholesterol esters
Phospholipids
Glycolipids

3

What is a fatty acid?

A long hydrocarbon chain with a terminal carboxyl group

4

What is energy from dietary lipids mainly dependant on?

Chain length

5

How many double bonds does saturated fatty acid have?

0

6

How many double bonds does monounsaturated fatty acid have?

1

7

Short chain fatty acids (4)

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

8

Medium chain fatty acids (4)

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

9

Long chain fatty acids (2)

Greater than 14 carbons
Main constituent of dietary fat

10

Where does fatty acid synthesis occur?

Cytosol

11

Which compound does fatty acid synthesis require?

Acetyl CoA

12

Explain C18:2 cis 9, 12 (3)

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

13

Explain C18:2 n-6 (3)

18 carbons
2 double bonds at carbon 6 counting from the methyl end

14

Which pathway does 6-desaturase prefer and why?

N-3
To ensure essential fatty acids are produced

15

Explain lipid re-esterification during absorption process (4)

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

16

The common saturated fat (2)

Palmatic acid C16:0
Stearic acid C18:0

17

Common monounsaturated fat

Oleic acid C18:1

18

Common polyunsaturated fats (2)

Linoleic acid C18:2
DHA C22:6

19

What form is most body fat stored as?

TAG

20

Fatty acid synthesis in the cytosol (5)

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

20

Enzymes of fatty acid synthesis in the cytosol (4)

Acetyl CoA carboxylase
Fatty acid synthase
Elongase
9-desaturase

20

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

All fatty acid pathways use this enzyme
It's the key enzyme that determines which PUFAs are produced

20

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

50-100g per day
35-40% total energy

21

Why are dietary lipids important?(8)

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

23

Explain the gastric stage of TAG digestion (5)

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

24

Duodenal phase of digestion (6)

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

25

What does pancreatic lipase do?(3)

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

26

How are fats solubilised?(2)

By associating with bile salts and forming micelles

27

Why must fats be emulsified?(3)

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

28

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

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

29

Chylomicron metabolism (4)

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

30

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

It becomes a chylomicron remnant
It is then removed from the blood by the liver

31

What is the function of plasma lipoproteins (2)

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

32

Role of LDL

Transport cholesterol from liver to body tissues

33

Role of VLDL

Transport newly synthesised TAG from liver to peripheral tissues

34

Role of HDL

Transport cholesterol from tissues to liver

35

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

Linoleic acid C18:2, n-6
a-linolenic acid C18:3, n-3

36

Potential consequences of essential fatty acid deficiency (2)

Increase permeability to water and small molecules
Reduced efficiency of oxidative phosphorylation in mitochondria

37

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

FAs

38

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

Brain
Kidney medulla
Eye

39

Classes of lipids (4)

Simple
Complex
Derived
Miscellaneous

40

Examples of simple lipids (3)

FAs esterified with glycerol
TAG
Waxes

41

Example of complex lipids (3)

Phospholipids
Glycolipids
Lipoproteins

42

Examples of derived lipids (3)

Saturated fats
Monounsaturated fats
Polyunsaturated fats

43

Major biological roles of FAs (4)

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

44

Sources of palmitic acid (3)

Meat
Dairy products
Palm oil

45

Sources of oleic acid (3)

Meat
Dairy products
Olive oil

46

Stearic acid sources (3)

Animal fats
Vegetable fats
Cocoa butter

47

Linoleic acid sources (2)

Sunflower oil
Corn oil

48

DHA sources

Oily fish

49

What are bile salts?(3)

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

50

What is FA transport across the membrane dependent on?

Inward diffusion gradient

51

What happens to bile acids during absorption (4)

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

52

Where do LCFAs originate from?(3)

Diet
Synthesis of acetyl CoA
Elongation of SCFA

53

Stages of TAG digestion (3)

Gastric
Duodenal
Ilial

54

Production of PUFAs (3)

Derived from MUFA
Double bond inserted into LCFAs
Uses desaturase enzyme

55

What is co-lipase?(3)

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

Where does the majority of fat absorption occur?

Jejunum

57

When does fat absorption occur?

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

58

Fat absorption process (3)

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

59

Why are some fatty acids essential?(2)

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

60

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

Oleic acid C18:1
C18:2
C20:2
C20:3
C22:3
C24:4

61

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

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

62

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

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

63

Which essential fatty acid is a component of the retina?

DHA

64

Roles of eicosanoids (3)

Mediate variety of cellular functions
Local hormones
Modulate inflammatory response

65

Which cellular functions do eicosanoids mediate?(2)

Smooth muscle contraction
Platelet aggregation (Blood clotting)

66

Role of eicosanoids as local hormones (2)

Paracrines
Autocrines

67

How do eicosanoids modulate inflammatory responses?(3)

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

68

What are eicosanoids?

Derivatives of omega 3 and omega 6

69

Which type of fatty acid produces more potent eicosanoids?

Omega 6

70

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

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

71

What are conjugated linoleic acids?

Linoleic acids which have double bonds next to each other

72

How are CLAs produced?(3)

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

Potential health benefits of CLAs (5)

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

74

How much energy does a gram of fat produce?

39.1kJ

75

What are the two predominant CLAs?

Cis-9, trans 11
Trans 10, cis 11

76

What are micelles?(3)

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