Title: Chemistry of lipids
1Chemistry of Lipids
R.C. Gupta Professor and Head Dept. of
Biochemistry National Institute of Medical
Sciences Jaipur, India
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5Classification
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8Fats are rich in saturated fatty acids oils are
rich in unsaturated fatty acids
Fat
Oil
9CH3?(CH2)15?OH
Cetyl alcohol
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18 19 20Fatty acids
21Fatty acids(contd)
Each fatty acid possesses a carboxy terminal and
a methyl terminal
The carbon atoms are numbered from the carboxy
terminal, the carboxyl atom being numbered 1
22Fatty acids(contd)
23Some saturated fatty acids
Fatty acid Formula Fatty acid
Formula Acetic acid CH3COOH
Propionic acid C2H5COOH Butyric acid
C3H7COOH Caproic acid
C5H11COOH Caprylic acid C7H15COOH
Capric acid C9H19COOH Lauric acid
C11H23COOH Myristic acid
C13H27COOH Palmitic acid C15H31COOH
Stearic acid C17H35COOH Arachidic acid
C19H39COOH Behenic acid
C21H43COOH Lignoceric acid C23H47COOH
Cerotic acid C25H51COOH
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26Some fatty acids have a ring in their
acyl chain e.g. chaulmoogric acid
- Chaulmoogric acid was used as an
anti-leprosy drug in the past
27Monounsaturated fatty acids
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29Palmitoleic acid
Formed from palmitic acid
Formula is CH3(CH2)5CHCH(CH2)7COOH
30Polyunsaturated fatty acids
31Polyunsaturated fatty acids (contd)
32Polyunsaturated fatty acids (contd)
33Polyunsaturated fatty acids (contd)
34Essential fatty acids
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37- EFA are the precursors of hormone-like
compounds known as eicosanoids
38Eicosanoids
39Tissue distribution of eicosanoids was later
found to be very wide
They produce profound physiological and
biochemical effects on various organs and systems
Systems affected by them include reproductive
system, cardio-vascular system, central nervous
system, gastro-intestinal tract etc
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43The other eicosanoids are thromboxanes and
leukotrienes They also produce profound
physiological effects
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46Leukotriene E4 (LTE4)
Leukotriene C4 (LTC4)
Leukotriene D4 (LTD4)
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49G
Glycerol
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53The fatty acids present in a triglyceride are
generally different from each other
R1, R2 and R3 represent the acyl groups of fatty
acids
The first fatty acid is generally saturated the
second and the third are generally unsaturated
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62Two molecules of phosphatidic acid are linked,
through their phosphate groups, with a molecule
of glycerol in diphosphatidyl glycerol
(cardiolipin)
63In plasmalogens, an unsaturated alcohol is linked
with carbon 1 of glycerol by an ether bond
64Sphingophospholipids contain sphingosine as the
alcohol portion Sphingosine is a long chain
amino alcohol which is synthesised from palmitic
acid and serine
65The most important sphingophospholipid in
our body is sphingomyelin
It is a constituent of nervous tissue and
membranes
It is made up of sphingosine, a fatty
acid, phosphoric acid and choline
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72Cerebrosides
- Cerebrosides are glycolipids containing
sphingosine, a fatty acid and galactose
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74Kerasin contains
Nervon contains
Oxynervon contains
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79Lipoproteins
Lipids are an important source of energy for us
As they are insoluble in water, their
transport in plasma poses a problem
This problem is solved by combining the
more insoluble lipids with more polar ones
and then combining them with some proteins
The complex, so formed, is known as a lipoprotein
80EMB-RCG
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84Ultracentrifugation
85After a few hours, four different layers are
formed
From above downwards, these are
Chylomicrons (CM)
Very low density lipoproteins(VLDL)
Low density lipoproteins
(LDL) High density
lipoproteins (HDL)
86Electrophoresis
87Four different bands are formed
From point of application, these
are
Chylomicrons (CM)
b-Lipoproteins
Pre-b-lipoproteins
a-Lipoproteins
88Same as
Pre-b-lipoprotein
VLDL
LDL
Same as
b-Lipoprotein
Same as
a-Lipoprotein
HDL
89Steroids
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94- Cholesterol is the precursor of many important
compounds in our body e.g. vitamin D3, steroid
hormones, bile acids and bile salts -
If an excess of cholesterol is present in plasma,
it tends to get deposited in the walls of
arterioles causing atherosclerosis
95Physical properties of lipids
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97- Such lipids are said to be amphipathic i.e. a
part of the molecule is polar and a part non-polar
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106 Unsaturated fatty acid with cis double bond
107Chemical reactions of lipids
108Hydrolysis
The ester bonds of lipids can be hydrolysed by
specific enzymes
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110Saponification
111Hydrogenation
- Double bonds of unsaturated fatty acids can be
hydrogenated in the presence of catalysts e.g.
nickel
H H
112Iodination
Iodine can also reduce the double bonds of
unsaturated fatty acids
I2
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114Iodine number of common oils
115Oxidation
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117- Fat which undergoes this type of oxidation
becomes rancid - Rancid fat is unpleasant in taste and smell, and
can be toxic - Rancidity is prevented by anti-oxidants e.g.
vitamin E
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119In Salkowskis reaction, cholesterol is treated
with concentrated sulphuric acid
It is dehydrated to cholestadiene and its
polymers which are red in colour
120In Liebermann-Burchard reaction, cholesterol is
treated with concentrated sulphuric acid and
acetic anhydride
It is dehydrated to cholestadiene and its
polymers which are sulphonated to form a green
or blue complex
121Thank you