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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
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

Fundamentals (17 decks)

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