The document discusses lipids and fatty acids. It defines lipids as organic substances that are insoluble in water but soluble in organic solvents. Lipids are classified into simple, compound, derived and miscellaneous lipids. Fatty acids are the most common components of lipids in the body. They are aliphatic carboxylic acids with hydrocarbon side chains. Saturated and unsaturated fatty acids occur naturally. Phospholipids are an important class of compound lipids that form structural components of biological membranes and are involved in various metabolic functions. The most abundant phospholipid is lecithin, which contains phosphoric acid esterified to glycerol and choline.

1. Akshai George Paul

2.  Lipids may be regarded as organic substances insoluble
in water, soluble in organic solvents.

3.  Lipids are classified into:
I. Simple lipids
II. Compound lipids
III. Derived lipids
IV. Miscellaneous lipids

4. Esters of fatty acids with alcohols.
 Fatty acids: Aliphatic carboxylic acid
with hydrocarbon side chain.
General formula
R-CO-OH
 Where COOH – carboxylic group is the functional
group.

5.  Depending upon the R- group( hydrocarbon chain), the
physical properties of fatty acids are vary.
 Mainly two types:
a) Fats and oils: Esters of fatty acids with glycerol.
b) Waxes : Esters of fatty acids with alcohol other than
glycerol.

6.  Esters of fatty acids with alcohol containing additional
groups such as phosphate, nitrogenous base,
ceroprotein etc.
1. Phospholipids
2. Glycolipids
3. Lipoprotein
4. Other compound lipids.

7.  Lipids containing phosphoric acid
 Two main types
a) Glycerophospholipids : Phospholipids containing
glycerol and alcohol.
Eg: lecithin
b) Sphingophospholipids : Spingosin is the alcohol.
Eg: spingomyelin.

8.  Contains fatty acids, carbohydrates and nitrogenous
base.
 Spingosine is the alcohol.
 Also called glycosphingolipids.
 Glycerol and phosphate are absent.

9.  Macromolecular complexes of lipids and proteins.
 Sulpholipids
 Aminolipids
 Lipopolysaccharides

10.  Compounds which are derived from lipids or
precursors of lipids.
 Eg: Fatty acids, steroids eisosanoinds

11.  Large number of compounds possessing the
characteristics of lipids.
 Eg: carotinoids.

12.  Fatty acid are included in the gp of derived
lipids.
 Most common component of lipids in the
body

13. I.Depending on total number of carbon atoms
1. Even chains
2. Odd chains
II. Depending on lengh of hydrocarbon chain
1. short chain with 2-6 carbon atoms
2. medium chain with 8-14 carbon atoms
3. long chain with16-22 carbon atoms
4. very long chain fatty acids (more than
than24 carbon)

14. III. Depending on the nature of hydrocarbon chain
1. saturated fatty acids
2. unsaturated fatty acids
3. branched chain fatty acids
4. hydroxy fatty acids

15.  Most of the fattyacids occur in nature are of
even chain carbons(14C-20C)
 Due to the fact that biosynthesis of fattyacids
mainly occurs with the sequential addition of
two carbon units
 Eg: palmitic acid(16C)
 Stearic acid (18C)

16.  Propionic acid (3C)
 Valeric acid (5C)

18.  Both saturated and unsaturated fattyacid equally occur in the
natural lipids.
 They have general formula
CH3-(CH2)n-COOH
 Saturated fattyacids do not contain double bonds
 The carbon atoms of fattyacids are numbered as C1, C2 etc
starting from the methyl end the carbon atoms may be
numbered as omega(ω)1 2 3

19. 6 5 4 3 2 1
 CH3-CH2-CH2-CH2-CH2-COOH
ω1 ω2 ω3 ω4 ω5 ω6
They are named by adding the suffix ‘anoic’ after the
hydrocarbon
eg: Caproic acid

21.  They are named by adding suffix ‘enoic’ after the
systemtic name
 Fattyacids with one double bond are known as
monounsaturated and those with 2 or more double
bonds are collectively known as polyunsaturated
fattyacid(PUFA)

22.  The general rule is that the total number of atoms are
written first , followed by the number of double bonds
and finally first carbon position of double bond, starting
from the carboxyl end
 Eg: saturated fattyacid palmitic acid is written as 16:0
 Oleic acid 18:1;9
 Arachidonic acid 20:4;5,8,11,14

23.  The fatty acid that cannot be synthesized by
the body , and therefore should be supplied
in the diet are known as essential
fattyacids(EFA)
 Eg: LINOLEIC ACID
LINOLENIC ACID

27.  Present in diary products.
 Injurious to health.
 Oils containing PUFA.
 Have high content of TFA.

28.  Fast food preparations have high TFA contents.
 TFA adversely affect multiple risk factors including
endothelial dysfunction, diabetes and adiposity.

29. 1. Hydrogenation
 Unsaturated fatty acids may be converted
to the corresponding saturated fatty acids by
hydrogenation of the double bonds.
Linolenic +2H Linoleic +2H Oleic +2H Steric
 Hydrogenation of oils can leads to solidification and
saturation
 Eg: vanaspathi

30.  When treated with halogens under mild conditions the
unsaturated fatty acids can take up two halogen atoms
at each double bond to form the halogenated derivative
of the fatty acid.
 Oleic acid + I2 Di-iodo oleic acid
 The number of halogen atoms takenup will depend on the
number of double bonds and is an index of the degree of
unsaturation.

31. Increase in chain lengh and degree of saturation
(decrease in number of double bonds)lead to increase in
melting points.
So, long chain fattyacid have high melting points than
medium and short chain fattyacids .

32. Similarly, saturated fattyacid have higher melting point than
unsaturated fattyacid.
Among the unsaturated fattyacid ,monounsaturated fattyacid
have higher melting point than the polyunsaturated fattyacid.
 Steric acid C18 MP (690C)
 oleic acid (C181;9)MP(130C)

33.  Saturated and unsaturated fatty acids form salts with
alkali.
 CH3-COOH + NaOH CH3-COONa +H2O
 Sodium and potassium salts of long chain fatty acids
are called soaps .

34.  Both saturated and unsaturated fatty acids form esters
with alcohols especially with glycerol.
 Fatty acids can form mono, di or tri-esters with alcohol
groups of glycerol.
 Triglycerides or triacylglycerols are also called Neutral
fat.

35.  Glycerol + fatty acid Monoacylglycerol
 Monoglycerides + fatty acids Diacylglycerol
 Diglyceride + fatty acid TRIGLYCERIDE OR
TRIACYLGLYCEROL

36.  All fatty acids undergo oxidation in the body to give
energy.
 Beta oxidation is the major process by which acids are
oxidised.

37.  1.FATS AND OILS (TRIACYL GLYCEROL OR
NEUTRAL FATS)
 2.WAXES

38.  Neutral fats are also called triacylglycerols(TAG) or
triglycerides(TG)
 Esters of glycerol with fattyacids

39. O
CH2-O-C-R
HO-CH
CH2OH
O CH2OH
R-C- O-CH
CH2OH
2-Monoacylglycerol1-Monoacylglycerol

40. O
O CH2-O-C-R1
R2-C- O-CH
CH2OH
O
O CH2-O-C-R1
R2-C- O-CH O
CH2-O-C-R3
1,2- Diacylglycerol Triacylglycerol

41. CH2-O-CO-R
1
R-CO- O-CH
2
CH2-O-CO-R
3
α (1)
β (2)
α1 (3)

42.  Monoacylglycerol, diacylglycerol and triacylglycerol
respectively consisting of one , two,three molecules of
fattyacids esterified to a molecule of glycerol.
 The carbon atoms of glycerol are designated as α, β and
α1 as 1,2,3 where R represents the side chain of fatty
acids

43.  Naturally occuring fats and oils are mixtures of
triglycerides
 If all the three hydroxyl gps of the glycerol are esterified
to the same fattyacid a simple triacyl glycerol is formed
 Eg: Tripalmitin, Triolein etc.
 Amixed TG is formed when different fattyacid are
esterified to the hydroxyl gps of glycerol

44.  Generally two hydroxyl gps are esterified to similar
fattyacid and the third with a different one
 Eg: 1,3 dipalmitoyl -2 olein ,1 palmitoyl-2,3 distearin
 When a PUFA is present it is commonly esterified to
the second or beta carbon atom.

45.  They are hydrophobic and insoluble in water
 Oils are Liquids: 20 degree , they are triglycerides
which contain a higher proportion of unsaturated
fattyacids or short chain chain triglycerides oils are
generally of plant origin
 Fats are solids:at room temperature and contain mainly
saturated long chain fatty acids .Fats are mainly of
animal origin.

46.  When the fattyacids have a higher chain lengh and are
predominantly saturated hard fat is formed
 Eg: pig fat
 Fats containing medium chain TG or unsaturated
fattyacids are soft fats
 Eg:butter, coconut oil
 coconut oil contains mainly medium chain TAG

47.  The triacylglycerols are the storage form of lipids in
the adipose tissue.
 In a 70kg normal person body stores about 11kg of
triacylglycerol. Which is roughly equivalent to
100,000kcal

48.  This occurs in the body during digestion of dietary fat
and mobilization of TAG from adipose tissue .
 TG in the body are hydrolysed by enzymes,lipase.
Triacyl glycerol is sequentially hydrolysed to diacyl
glycerol and monoacyl glycerol and finally glycerol
plus 3 fattyacid.

49. Triacylglycerol
Diacylglycerol
Monoacylglycerol
Glycerol + Fatty acid
Lipase
Lipase
Lipase
H2O
Fatty acid
H2O
Fatty acid
+ H2O

50.  When TG are hydrolysed by alkali the process is
known as saponification
 The products are glycerol and soaps

51. CH2-O-CO-R1
CH-O-CO-R2
CH2-O-CO-R3
CH2OH
CHOH
CH2OH
+
3R
COONa
(+)3 NaOH
GlycerolTG

52.  It is defined as the mg (number) of KOH required to hydrolyse
(saponify) one gram of fat or oil.
 Fatty acids present in TAGs react with alcoholic KOH or NaOH to
produce glycerol and fattyacid salt of alkali metal
 Eg:Pottassium Stearate from stearic acid . Such salts have soaps
like properties .This process of formation of soap is called
 SAPONIFICATION OF FAT
 TRISTEARIN+KOH 3-POTASSIUM
STEARATE+GLYCEROL

53.  Iodine number of a fat is defined as the number of gms
of iodine taken up by 100 gms of iodine of fat.
 It is an index of the degree of unsaturation and is
directly proportional to the content of unsaturated
fattyacids. Higher the iodine number higher is the
degree of unsaturation
 Ex:I N: of butter is 28
 sunflower oil is 130

54.  Fats and oils have a tendency to become rancid , the
term rancidity refers to the apperance of an unpleasant
smell and taste for fats and oils
 HYDROLYTIC RANCIDITY
 Due to partial hydrolysis of the TG molecules due to
traces of hydrolytic enzymes present in naturally
occurring fats and oils

55.  Partial oxidation of unsaturated fattyacids with resultant
formation of epoxides and peroxides of small molecular wt
fattyacids by peroxides and free radicals .
 Many natural fats and oils may contain antioxidants (eg:vit:E)
which prevent the occurrence of oxidative rancidity
 PUFA are more easily oxidised ; so vegetables oils with a high
content of PUFA are usually preserved with adition of
antioxidants.

56.  Repeated heating of oils would lead to the formation
and polymerization of cyclic hydrocarbons . These will
impart an unpleasant smell taste and colour to the oil
 Coconut oil having medium chain saturated fatty acid
will withstand such polymerization

57.  They are esters of higher fattyacids with higher
monohydroxy alipatic alcohols and so have long
straight chains of 60- 100 chains
 They are used as the base for the preparation of
cosmatics ointments polishes candles etc.

58. COMPOUND LIPID
 1. PHOSPHOLIPID
 2. GLYCOLIPID( cerobrosides gangliosides)
 3. LIPOPROTEIN
 4. OTHER COMPLEX LIPID(sulpholipids)

59. PHOSPHOLIPIDS
1. GLYCEROPHOSPHOLIPID
2. SPHINGOPHOSPHOLIPID
GLYCEROPHOSPHOLIPIDS
1.With nitrogenous base
a.Cephalin
b.Lecithin
c.Phosphatidyl serine
d.Plasmalogens
2.Without nitrogenous base
Phosphatidyl enositol

60.  These are complex or compound lipids
containing phosphoric acid in addition to
fatty acids nitrogenous base and alcohol
 Phospholipids are the main lipid constituent
occur in biological membrane

61.  Phospholipids constitute an imp:gp of
compound lipid that perform a wide variety
of funtions
 In association with proteins phospholipids
form the structural components of
membranes and regulate the membrane
permeability
 Phospholipids (lecithin cephalin and
cardiolipin) in the mitochondria are
responsible for maintaining the conformation

62.  Phospholipids are essential for the synthesis
of different lipoproteins and thus participate
in the transport of lipids
 Accumulation of fat in liver (fatty liver )can be
prevented by phospholipids , hence they are
regarded as lipotropic factors
 Arachidonic acid an unsaturated fattyacid
liberated from phospholipids serves as a
precursor for the synthesis of eicosanoids
(prostaglandins prostacyclins thromboxanes
etc……………..

63.  Phospholipids (phosphatidyl inositol)are
involved in signal transmisson across
membrane.

64.  Simplest phospholipid
 Phosphatidic acid is made up of one glycerol
to which two fattyacid residues are esterified
to carbon atoms 1 and 2 .
 The third hydroxyl gp is esterified to a
phosphoric acid

66.  Most abundant gp of phospholipid in the cell
membrane
 Chemically lecithin (Greek :lekithos-egg yolk)
is a phosphoric acid with choline as the base
 The alpha and beta positions are esterified
with fattyacidS ,Usually the fattyacid attached
to the beta carbon is a PUFA molecule

68.  The phosphoric acid is added to the third
position to form phosphatidic acid , the
phosphate gp is estrified to nitrogen base
choline
ACTION OF PHOSPHOLIPASES
 Phospholipases are enzymes that
hydrolyse phospholipids

69. 1
2
3 4

70. 1. site of action of phospholipase A1
2. site of action of phospholipase A2
3. site of action of phospholipase C
4. site of action of phospholipase D

71.  Lecithin lysolecithin + fatty acid
 Lecithin Acyl glycerophosphoryl choline +fatty acid
 Lecithin 1,2 diacyl glycerol + phosphoryl choline
 Lecithin phosphatidic acid + choline
Phospholipase A2
Phospholipase A1
Phospholipase C
Phospholipase D

72.  Different phospholipases are involved in the
hydrolysis of specfic bonds in lecithin
 Phospholipases A2 acts on an intact lecithin
molecule hydrolying the fattyacid esterified to
the beta (second) carbon atom , the products
are lysolecithin and fattyacid.
 Lysolecithin is a detergent and hemolytic
agent.

73.  Normal lung function depends on a constant
supply of lung surfactants.
 It is produced by epithelial cells.
 It decreases the surface tension of the
aqueous layer of lung and prevent collapse
of lung alveoli.

74.  Constituents of surfactants are dipalmitoyl
lecithin, phosphatidyl gycerol, cholesterol and
surfacet proteins A B C.
 During fetal life the lung synthesis
sphingomyelin before 28th week of gestation ;
but us fetus matures , more lecithin is
synthesized.
 The lecithin sphingomyelin (LS) ratio of
amniotic fluid is an index of fetal maturity.
 A ratio of 2 indicates fall lung maturity .


75.  Low levels of surfactants leads to respiratory
distress syndrome (RDS) which is a common
cause of neonatal morbidity
 RESPIRATORY DISTRESS SYNDROME (RDS)
It is due to a defect in the biosynthesis of
dipalmitoyl lecithin(DPL) is the main
pulmonary surfactants.
Premature infants have a higher incidence of
RDS, because the immature lungs, do not
synthesis enough DPL.

76.  Cephalin differs from lecithin in that the
nitrogen base ethanol amine is present
instead of choline, cephalin is also found in
biomembrane and possesses amphiphathic
properties.

78.  When a fattyacid is attached by an ether linkage
at C1 of gycerol in the glycerolphospholipid the
resultant compound is plasmalogen.
 The second OH gp is esterified to a fattyacid the
phosphoric acid is attached to choline or ethanol
amine
Plasmalogens are found in biomembranes brain
and muscle.

80.  The aminoacid serine is present in this gp of
glycerophospholipids.

82.  Phosphatidic acid is esterified to inositol is
phosphatidyl inositol
 Bisphosphate or PIP2 is present in
biomembranes
 This compound plays a vital role in the
mediation of hormone action on biomembranes
and acts as a second messenger.

84.  It is formed by esterification of phosphatidic
acid to glycerol . When 2 molecules of
phosphatidic acid are linked with a molecule
of glycerol ,diphosphatidyl glycerol or
cardiolipin is formed.
 It is the major lipid of mitochondrial
membrane
 Decreased cardiolipin level leads to
mitochondrial dysfuntion.

86.  The sphingosine containing lipids may be of
3 types
 1. PHOPHOSHINGOSIDES
 2. GLYCOSPHINGOLIPIDS
 3. SULFATIDES

87.  Sphingosine is an alcohol present in
sphingomyelin
 Sphingosine is attached by an amide linkage
to a fatty acid to produce ceramide.

88. Contain phosphoric acid group
A common phosphosphingoside present
abundantly in biomembrane-sphingomyelin it
contain choline

90.  Only sphingomyelin that contain phosphate
and have no sugar moiety.
 Found in large quantities in nervous system .
 Different sphingomyelin may be formed
depending on the fattyacid attached.
common fattyacid are lignoceric acid(24c)
nervonic acid(24c) etc………

91.  Because of its amphipathic nature
sphingomyelin can act as an emulsifying
agent and detergent
 Relative proportion of lecithin and
sphingomyelin is imp:in biological fluids like
bile amniotic fluid
 Sphingomyelin combined with fattyacid is
called ceramide

92.  GLYCOSPHINGOLIPIDS(GLYCOLIPIDS)
 Seen widely in nervous tissues .
 Do not contain phosphoric acid
 Instead they contain CHO and ceramide

93.  Ceramide + glucose glucocerebroside
Ceramide+ galactose galactocerebroside

94.  They contain 2 or more hexoses or
hexoamines attached to a ceramide molecule
 Ceremide+galactose+glucose lactosyl
 ceramide
 Lactosyl ceramide is a component of
erythrocyte membrane

95.  They are formed when ceramide oligo-
saccharides have atleast one molecule of
NANA(N-acetyl neuramic acid sialic
acid)attached to them.
 Ceramide –Glucose –Galactose -NANA-
predomintly found in ganglions.

96.  Lipoproteins are molecular complexes of
lipids with proteins they are the transport
vehicles for lipids in the circulation they are
five types of lipoproteins .
 A lipoprotein basically consists of a neutral
lipid core (with triacylglycerol/cholesteryl
ester sorrounded by a coat shell of
phospholipids apoproteins and cholesterol).

97.  The polar portions (amphiphilic) of
phospholipids and cholesterol are exposed
on the surface of lipoproteins so that
lipoprotein is soluble in aqueous solution.
 CLASSIFICATION OF LIPOPROTEIN
 Five major classes of lipoproteins are
identified in human plasma, based on their
separation by electrophoresis.

98.  1.CHYLOMICRONS: They are synthesized in
the intestine and transport dietary TG to
various tissues .
 They consists of higher (99%)quantity of lipid
and lowest (1%)concentration of protein.
 2. VLDL : Produced in liver and intestine
helps in transport of endogenously
synthesized TG.

99. 3. LDL: They are formed from VLDL in the
blood circulation . They transport
cholesterol from liver to other tisssues .
4. HDL: Synthesized in liver .HDL particles
transport cholesterol from peripheral
tissues to liver.
5. Free fatty acid : Free fattyacids in the
circulation are in a bound form to albumin
each molecule of albumin can hold about
20- 30 molecules of free fattyacids.

101.  Formed when sulfate gps are attached to
ceramide oligosaccharides
 Imp:components of membranes of nervous
tissues .
 Failure of degradation of these compounds
results in accumulation of these complex
lipids in CNS.
 This gp of inbornerrors is known as lipid
storge disease.

102.  As per definition lipids are insoluble
(hydrophobic in water)
 This is primarily due to the predominant
presence of hydrocarbon gp.
 Some of the lipids possess polar or
hydrophilic gps . Which tend to be soluble
in water

103.  Molecules which contain both hydrophilic
and hydrophobic gps are known as
amphipathic (Greek :amphi:both-pathos –
passion)
EXAMPLES OF AMPHIPATHIC LIPIDS
Among the lipids ,fattyacids , phospholipids
sphingolipids bilesalts and cholesterol are
amphipathic in nature .
Phospholipids are amphipathic particularly
lecithin .

104.  Having both hydrophobic and hydrophilic
portion
 The glycerol along with the phosphoric acid
and choline constitute the polar head of a
phospholipid molecule . Where as the
hydrocarbon chains of the fattyacid represent
the non polar tail.

105.  When the amphipathic lipids are mixed in water
(aqueous phase) the polar gps (head)orient
themselves towards aqueous phase while the non
polar (tails)orient towards the opposite directions
this leads to the formation of micelles.
 They are involved in solubilization of lipids
inaqueous media and help in digestion and
absorbtion.

106.  They are produced when amphipathic lipids
in aqueous medium are subjected to
sonification.
 Liposome on the other hand, aggregate in a
manner that they enclose an aqueous phase .
In this interior interior aqueous phase , drugs
and other agents can be packed for delivery
to specfic sites for treatment.
 They are of potential use for gene transfer

107.  The molecules align themselves to form
monolayers with the polar heads pointing in
one direction and the non polar tails in the
opposite direction
 Only fattyacids with more than 6 carbon
atoms form monolayers .
 The self assembly of phospholipids into
bilayers is driven by hydrophobic interaction .

108.  They also act as detergents and emulsfying
agents.
 Invivo , they act as pulmonary surfacts

113.  Steroids are the compounds containing a
cyclic steroid nucleus (ring) namely
cyclopentanoperhydrophenanthrene (CPPP)
 It is a fused ring system made up 3
cyclohexane rings designated as A B & C and
a cyclopentane ring D.
 Total 19 carbon atoms .

114.  The methyl side chains (19 & 18 ) attached to
carbons 10 & 13 , at carbon 17 steroids
usually contain a side chain .
 There are several steroids in biological
system . These include cholesterol , bileacids
vitamin D sex hormones and adrenocortical
hormones.
 If the steroid contains one or more hydroxyl
gps . It is commonly known as sterol (means
solid alcohol).

116.  Cholesterol is exclusively found in animals
and is the most abundant animal sterol.
 It is widely distributed in all cells and is a
major component of cell membrane and
lipoproteins
 Cholesterol (Greek –chole-bile )was first
isolated from bile.
 Cholesterol literally means solid alcohol from
bile.

117.  Structure of cholesterol(C27H46O)
 One hydroxyl gp at C3 and a double bond
between C5 $ C6, .An 8 carbon aliphatic
chain is attached to C17.
