Chapter 3: Lipid Chemistry Flashcards
1
Q
What are lipids?
A
Organic compounds insoluble in water but soluble in organic solvents. Eg. Chloroform, ether, benzene, and acetone.
2
Q
What is the lipid’s biomedical importance?
A
They provide the body with a source of energy: lipids have a high energy value.
They provide the body with essential vitamins : vitamins K, E, D, A.
They provide the body with essential fatty acids: Linoleic, and a linoleic acids.
3
Q
What are the compartments the lipids are found in the body?
A
Plasma, adipose tissue, and cell membrane.
4
Q
What are types of lipids?
A
Simple lipids, conjugated lipids, and derived lipids.
5
Q
Simple lipids
A
Esters of fatty acids with alcohols.
6
Q
Conjugated lipids
A
Simple lipids conjugated with another group. Eg. Phospholipids or glycolipids.
7
Q
Derived lipids
A
Product of hydrolysis of lipids or substance associated with lipids in nature.
8
Q
Fatty acids
A
Monocarboxylic organic acids that mostly contain an even number of carbon.
9
Q
Fatty acids occurrence
A
Esterified with alcohols: in natural fat, oils, and waxes.
Unesterified: in plasma carried by albumin (FFA).
10
Q
Fatty acids are classified according to?
A
Whether they have a double bond or not.
Saturated: contains no double bonds.
Unsaturated: contains I or more double bonds.
11
Q
Saturated fatty acids
A
No double bonds.
12
Q
Types of saturated fatty acids.
A
Short chain, medium chain, long chain, and very long chain.
13
Q
Short chain
A
C2-C4.
Examples: Acetic acid C2
Butyric acid C4
14
Q
Medium chain
A
C8-C10
Example: Capric acid C10
15
Q
Long chain
A
C12-C22
Examples: Palmetic acid C16
Steric acid C18
16
Q
Very long chain
A
C24 or more.
Example: Lignoceric acid C24
17
Q
Why are the palmitic and stearic acids the most important fatty acids?
A
Because they are widely distributed in diet.
18
Q
What is the commonest fatty acid in animals?
A
Palmitic acid.
19
Q
What are sources of saturated fatty acids?
A
Animal fat: cream and butter.
Vegetable products: coconut and Palm oil.
20
Q
Biomedical importance of saturated fatty acids.
A
Saturated fats acids increase cholesterol, this leads to increase atherosclerosis. This results in incidence of coronary heart disease (CHD).
21
Q
What are the two types of double bonds in unsaturated fatty acids?
A
Cis and trans.
22
Q
Cis type
A
Same side of double bond.
Allow bending of the chain at the double bond. The melting temperate is low, so they are liquid in room temperature.
23
Q
Trans type
A
Opposite side of the double bond.
Double bonds are linear are solid at room temperature.
24
Q
Where do naturally occurring unsaturated fatty acids contain?
A
Double bonds of the cis type.
25
What is the saturated fatty acids structure at room temperature?
Solid and linear.
26
How trans fatty acid produced?
It is during the hydrogenation of vegetable oil into margarine.
27
What are sources of trans fatty acids?
Baked food and cakes.
28
Trans FA biomedical importance
Saturated fats acids increase cholesterol, this leads to increase atherosclerosis. This results in incidence of coronary heart disease (CHD).
29
How are fatty acids classified according to their double bones?
Monoenoic ( monoethenoid) and polyenoic (polyethenoid).
30
Monoenoic (monoethenoid)
Contains only 1 double bond in their structure.
Present in animal and vegetable fat as olive oil.
31
Monoenoic (monoethenoid) biomedical importance
Decrease plasma cholesterol, this leads to the decrease of atherosclerosis. This results in decrease of incidence of coronary heart disease (CHD).
32
What are examples of Monoenoic (monoethenoid) double bonds?
1. Palmitoleic (16:1; omega 7)
2. Oleic (18:1, omega 9)
3. Nervonic (24:1; omega 9)
33
Polyenoic (polyethenoid)
Contains more than 1 double bond.
34
What are polyethenoids classified according to?
Their number of double bonds. Diethenoid, triethenoid, etc.
Each 2 double bonds are separated by a methylene group (-CH2).
35
Omega 6 PUFA
1st double bond at carbon 6 in relation to omega carbon.
36
Examples of omega 6 PUFA
1. Linoleic acid (18:2) parent FA
2. Arachidonic acid (20:4)
37
What are sources of omega 6 PUFA?
Nuts, olives, different oils such as sunflower, cotton seed, linseed, and corn oil.
38
What is the biomedical importance of omega 6 PUFA?
Decrease plasma cholesterol, this leads to the decrease of atherosclerosis. This results in decrease of incidence of coronary heart disease (CHD).
39
Omega 3 PUFA
First double bond at carbon 3 in relation to omega carbon.
40
Examples of omega 3 PUFA
1. a Linoleic acid (18:3) parent FA
2. Timnodonic acid (20:5)
41
What are the sources of omega 3 PUFA?
Plant oil like flax seed, canola, and fish oil.
42
Why is the biomedical importance of omega 3 Decrease plasma cholesterol, this leads to the decrease of atherosclerosis. This results in decrease of incidence of coronary heart disease (CHD).?
1. Decrease in cholesterol results in decrease in atherosclerosis and coronary heart disease.
2. Decrease in blood pressure.
3. Decrease in plasma tag.
4. Decrease in tendency of thrombosis.
43
Monoethenoid FA
Plamitoleic, oleic, and nervonic.
44
Diethenoid FA
Linoleic
45
Triethenoid FA
a Linoleic
46
Tetraethenoid FA
Arachidonic
47
Pentaethenoid FA
Timnodonic
48
Essential FA
FA that can’t be synthesized in the body and should be supplied in diet.
49
Essential FA’s are:
Linoleic and a Linoleic.
Other members of omega 3 and 6 are formed from Linoleic and a Linoleic by desaturation and elongation.
Arachidonic becomes essential in the absence of Linoleic.
Timnodonic becomes essential in the absence of a Linoleic.
50
What does the deficiency of essential FA’s lead to?
Children: retardation of growth and dermatitis.
Adults: fatty liver and sterility.
51
Ecasanoids
Derivatives of C20 like arachidonic acid and Timnodonic acid. They are hormone like molecules produced by most mammalian cells.
52
Where are eicosanoids active?
Within the cell they are produced (autocrine) or in adjacent cells (paracrine).
53
Advantages of Eicosanoids
Have many physiological and pharmacological actions.
54
What are types of Eicosanoids?
Cyclic Eicosanoids (prostanoids) and non cyclic Eicosanoids.
55
Cycle Eicosanoids
1. Prostaglandin (PG)
2. Prostacyclins (PGI)
3. Thromboxane (TX)
56
Non cyclic Eicosanoids
Leukotriens and lipoxins.
57
Simple lipids
Esters of FA with alcohol.
58
Simple lipids classification
According to the type of alcohol.
59
What are types of simple lipids?
Neutral fats (triglycerides) and waxes.
60
TAG
Esters of 3vFA with glycerol.
61
Waxes
Esters of FA with higher alcohols.
62
Glycerol
The alcohol present in TAG.
63
Fatty acids in TAG
Usually of different types (SFA and USFA).
64
TAGs are classified into two subgroups:
Oils and solid fats.
65
Oils
- have a low melting temperature.
- liquid at room temperature.
- examples: sunflower, cotton seed, linseed, and maize oils.
66
Solid fats
- high melting temperature.
- solid at room temperature
- examples: butter and margarine.
67
Waxes definition
Esters of long chain FA with long chain alcohols.
68
Waxes site
Trunks of trees or animal fur.
69
Waxes function
Acts as a protective coat.
70
Waxes examples:
1. True wax (Bess wax): esters of palmetic acid (16C) with mericyl acid (30C).
2. Cholesterol: lanolin (hair).
3. Vitamin A: retinol.
4. Vitamin D: calciferol.
71
Conjugated lipids
Simple lipids conjugated with another group.
72
Conjugated lipids are classified into:
Phospholipids: phosphate.
Glycolipids: carbohydrate.
73
Phospholipids are classified according to?
Alcohol present.
74
Phospholipids are classified into:
Glycerophospholipids (glycerophophotides): containing glycerol.
Sphingomyelin: containing sphingosine (sphingol).
75
Glycerophopholipids (glycerphophotides)
Phospholipids containing glycerol as alcohol.
Derivatives of phosphotidic acid.
76
Types of glycerophospholipids or phosphoglycerides.
1. Lecithin (phosphatidyl choline)
2. Cephalin (phosphatidyl ethanolamine)
3. Phophatidic acid
4. Phosphatidyl serine
5. Phosphatidyl inositol (lipostol)
6. Plasmalogen
7. Cardiolipins (diphosphatidyl glycerol)
8. Phosphatidyl glycerol.
77
Phosphatidic acid
1. Diacyglecerol phosphate.
2. FA at 1 is SFA and at position 2 is USFA.
3. Formed during synthesis of TAG and phospholipid.
4. Other phosphoglycerides are formed of conjugation with other groups.
78
Lecithin (phosphatidyl choline)
Phosphatidic acid + choline
79
Cephalons (ethanolamine)
Phosphatidic acid + ethanolamine
80
Phosphatidyl serine
Phosphatidic acid +serine
81
Phosphatidyl inositol (lipositol)
Phosphatidic acid + inositol
82
Plasmalogen
1. Ether of phospholipid but FA at position 1 is replaced by unsaturated fatty alcohol.
2. contains ethanolamine or choline.
3. Associated with Alzheimer’s disease.
83
Cardiolipins (Diphosphatidic glycerol)
1. Formed of 2 molecules of phosphatidic acid and 1 molecule of glycerol.
2. Hydrolytic products: 4FA’s, 3 glycerols, and 2 phosphates.
84
Phosphatidyl glycerol
Phosphatidic acid + glycerol
85
Phospholipases
Hydrolyzes different phospholipids.
86
Types of phospholipase
1. Phospholipase A1: SFA
2. Phospholipase A2: USFA
3. Phospholipase C: P
4. Phospholipase D: R, not in animal body.
87
Why does snake venom cause death?
It contains lecithinase (phospholipase A2), when injected to the blood it converts to phospholipids in cell membrane of RBC’s to lysophospholipids. This causes hemolysis.
88
Sphingomyelin location
In myelin sheath of brain and in cell membranes.
89
Sphingomyelin components
Contains alcohol sphingosine (sphingol) which contains 18 carbon atoms.
90
What makes up Sphingomyelin?
FA linked to sphingosine by amide bond forming ceramide.
Ceramide + phosphate + choline =Sphingomyelin.
91
Importance of Phospholipids
ALPHECH
1. Arachidonic acid
2. Lung surfactant are dipalmitoyl lecithin (DPL)
3. Platelet activation factor (PAF)
4. Hormone second messenger
5. Emulsification of fats
6. Call membrane and plasma lipoproteins
7. Hydrotropic substances
92
Arachidonic acid
For synthesis of Eicosanoids is obtained from cell membrane phospholipid.
93
Lung surfactants are dipalmitoyl lecithin (DPL)
1. Lecithin/Sphingomyelin (L/S) ratio is a marker for fetal lung maturity.
2. Lecithin and Sphingomyelin remain equal till 32-33 weeks of pregnancy.
3. After that lecithin increases markedly and Sphingomyelin remains the same.
4. L/S ratio should be 2 or more to indicate fetal lung maturity. If the ratio is less than 1.5 then it means Respiratory distress syndrome (RDS).
94
Platelet activating factor (PAF)
It is choline Plasmalogen (contains palmityl alcohol at CQ and acetic acid at C2.
95
Hormone second messengers (signal transduction)
1. Activation of G protein
2. Activation of phospholipase c
3. Hydrolyzes phosphatidyl inositol bi phosphate (PIP2) into:
- Inositol Tri phosphate (IP3): increases Intracellular Ca2+
- DAG: activates protein kinase C
* compounds that act through the activation of phospholipase C
- chemical transmitters: HSA, histamine, serotonin, acetylcholine.
- hormones: vasopressin -a-1 receptors for epinephrine and norepinephrine.
- growth factors
96
Emulsification of fat
As they are amphipathic compounds.
97
Cell membrane and plasma lipoproteins
1. As phospholipids are amphipathic, they form a phospholipid bilayer.
2. Increase USFA results in kink in due cis double bonds which keep the FA away from each other which results in the increase of fluidity.
3. Increase SFA interact strongly with each other which decreases fluidity.
98
Hydrotropic substances
Prevent precipitation of cholesterol as cholesterol stones.
99
Glycolipids
Formed of ceramide (sphingosine + FA) attached to carbohydrates.
Includes:
1. Cerebrosides
2. Sulfolipids or sulfatides
3. Gangliosides
100
Cerebrisides
1. Formed of ceramides
- Glucose (glucocerebrisides)
- Galactose (galactocerebrosides)
2. FA containing 24 carbons
- Lignoceric acid
- Nervonic
- Cerebronic acid (a hydroxyl Lignoceric)
101
Sulfolipids
102
Sulfolipids or sulfatides
Ceramide+ galactose 3 sulfate
103
Gangliosides
1. Ceramide + complex carbohydrate radicals, a mixture of glucose, galactose, and NANA.
2. FA usually contains 18C such as:
- Oleic acid
- Stearic acid
104
Importance of glycolipids
CMR
It is found in:
1. Cell membrane
2. Myelin sheath
3. Receptors for hormones
105
Choline containing lipids
1. Lecithin
2. Plasmalogen
3. Sphingomyelin
106
Phingolipids
1. Sphingomyelin
2. Glycolipids
- Cerebrosides
- Sulfolipids or sulfatides
- Gangliosides
107
Derived lipids
Produced by hydrolysis of simple or conjugated lipids or associated with lipids in nature.
108
Derived lipids include:
1. FA
2. Alcohols: glycerol and sphingosine
3. Steroids
4. Carotenoids
5. Fat soluble vitamins (vitamins K, E, D, A)
109
Steroids
Compounds containing steroid nucleus (cyclopentnoperhydrophenathrene) (CPPP).
110
Types of steroids
1. Sterols
2. Bile acids
3. Steroid hormones
111
Types of sterols
1. Zoosterols
2. Phytosterols
3. Mycosterols
112
Cholesterol structure
1. Most important sterol
2. Contains 27 carbons
3. OH at C3 and double bond between C5 and C6.
113
Cholesterol building units
Acetyl CoA (active acetate).
114
Plasma cholesterol
1. Synthesized by the liver
2. Normal range 120-200mg/dl (30% cholesterol and 70% cholesterol ester)
115
Cholesterol site
Nervous tissues (myelin sheath), gonads, and adrenals.
116
Cholesterol exertion
Mainly as bile salts.
Reduced by intestinal bacteria to dihydrocholestrol and coprostanol result is stool.
117
Cholesterol importance
Formation of:
1. Bile salt in the liver
2. Steroid hormones (in adrenals and gonads)
3. Vitamin D3 (cholecalciferol)
4. Cholesterol moderates membrane fluidity.
118
How does cholesterol moderate membrane fluidity?
At high temperatures, it prevents movement of fatty acids tail which decreases fluidity.
At low temperatures, it prevents close packing of phospholipids which increases fluidity and decreases gel formation.
119
Hazards of hypercholesterolemia
Predisposes to atherosclerosis and coronary heart diseases (CHD).
120
Phytosterols
Present in plants and are not physiologically important.
121
Mycocholesterols
Present in yeast and fungi as ergosterols which gives vitamin D2.
122
Steroid hormones
Sex hormones and corticoids.
123
Sex hormones
Male sex hormones (androgens):
1. Testosterone
Female sex hormones:
1. Estrogen: Estradiol E2
2. Progesterone
124
Corticoids
Glucocorticoid:
1. Cortisone
Meniralcorticoid:
1. Aldosterone
125
Caretenoids
Soluble pigments widely distributed in plants.
126
Caretenoids color
Yellow to red
127
Caretenoids plants
1. Orange
2. Apricot
3. Apple
4. Tomatoes
5. Carrots
128
Caretenoids animals
1. Animal fat (TAG)
2. Milk
3. Butter
4. Egg yolk
129
Medical importance of Caretenoids
PAS
1. Precursor of vitamin A which is important for vision and normal development.
2. Antioxidants: prevent cancer and atherosclerosis.
3. Stimulates the immune response against infection.
