Lipid chemistry, classification, properties and details of the Lipids, fatty acids and Lipoproteins are discussed. MBBS, BDS, BSc, MSc, Nursing etc

1. MNR MEDICAL COLLEGE & HOSPITAL
Dr Anurag Yadav
MBBS, MD
Assistant Professor
Department of Biochemistry
Instagram page –biochem365
Email: dranurag.y.m@gmail.com

2. OBJECTIVE
 Why do we need to study lipid chemistry
 Definition
 Functions
 Classification
 Fatty Acid

3. Constituents of diet
 Carbohydrates
 Proteins
 Lipids
 Vitamins
 Minerals
 water

4. Why do we need to study lipid
chemistry

9. DEFINITION:
The lipids are a heterogeneous group of
compounds,
have the common property of being
(1) relatively insoluble in water and
(2) soluble in non-polar solvents such as ether,
benzene and chloroform.

10. Functions of lipids
1) Structural components of cell membranes
(phospholipids, cholesterol)
2) Storage form of energy (triglycerides).

11. 3) Provides insulation against changes in external
temperature.
4) Give shape and contour to the body.
5) Protect internal organs by providing a
cushioning effect

12. 6) Acts as surfactant, prevents lung collapse.
7) They act as metabolic regulators (Steroid
hormones & Prostaglandinds- local hormones)
8) Helps in absorption of fat soluble vitamins in
food.

13. 9) Acts as electrical insulators – helps in
propogation of nerve
10) Lipids gives taste and palatability to food.

14.  Cell membrane
 Energy
 Insulation
 Shape
 Protects organs
 Surfactant
 Metabolic regulators
 Fat soluble vitamins
 Tasty food

15. CLASSIFICATION OF LIPIDS.
LIPIDS
SIMPLE
TAG
WAX
COMPOUND
DERIVED
OTHERS

16. SIMPLE LIPIDS
 Esters of Fatty acid with alcohol
 Ex- Fats & Oil
 Waxes

17. CLASSIFICATION OF LIPIDS.
LIPIDS
SIMPLE
TAG
WAX
COMPOUND
PHOSPHOLIPIDS
NON-PHOSPHOLIPIDS
DERIVED
OTHERS

18. COMPOUND LIPIDS
ADDITIONAL
GROUP
FATTY
ACID
ALCOHOL
PHOSPHOLIPIDS
NON-PHOSPHOLIPIDS

19. PHOSPHO
LIPIDS
NITROGEN
CONTAINING
GLYCEROPHOSPHO
LIPIDS
LECITHIN
CEPHALIN
NON NITROGEN
GLYCERPHOSPHO
LIPIDS
PHOSPHATIDYL INOSITOL
PHOSPHATIDYL GLYCEROL
DIPHOSPHATIDYL GLYCEROL
PLASMALOGENS CHOLINE PLASMALOGEN
ETHANOLAMINE PLASMALOGEN
PHOSPHO
SPHINOSIDES SPINGOMYELIN

20. NON
PHOSPHORYLATED
LIPIDS
GLYCOLIPIDS
CEREBROSIDES
GLOBOSIDES
GANGLIOSIDES
SULPHOLIPIDS
SULPHATED
CEREBROSIDES
GLOBOSIDES
GANGLIOSIDES

21. CLASSIFICATION OF LIPIDS.
LIPIDS
SIMPLE
TAG
WAX
COMPOUND
PHOSPHOLIPIDS
NON-PHOSPHOLIPIDS
DERIVED
FATTY ACIDS
STEROIDS
PROSTAGLANDINS
OTHERS
LIPOPROTEINS

22. FATTY ACIDS
 DEFINITON: fatty acids carboxylic acids with
hydrocarbon side chain
 General formula: R-CO-OH.

23. CLASSIFICATION OF FATTY ACIDS
FATTY
ACID
TOTAL NO.OF
C ATOMS
EVEN CHAIN
ODD CHAIN
LENGTH
OF CHAIN
SHORT CHAIN
MEDIUM CHAIN
LONG CHAIN
VERY LONG CHAIN
NATURE
OF
HYDRO
CARBON
SATURATED
UNSATURATED
BRANCHED CHAIN
HYDROXY FA

24. TOTAL NO.OF C ATOMS
EVEN CHAIN
• C4 butyric acid
• C6 caproic acid
• C8 caprylic acid
• C10 capric acid
• C12 lauric acid
• C14 myristic acid
• C16 palmitic acid
• C18 stearic acid
• C20 arachidic acid
ODD CHAIN
• C3 propionic acid

25. LENGTH OF CHAIN

26. SATURATED FATTY ACIDS
 Saturated FA do not contain double bonds
 General formula: CH3-(CH2)n-COOH.

29. UNSATURATED FATTY ACIDS
 FATTY ACIDS containing one or more double bonds
Subdivide as follows-
1. Monounsaturated- contain 1 double bond.
2. Polyunsaturated – contain 2 or more double bonds
3. Eicosanoids- derived from eicosa polyenoic fatty
acids, comprise of prostanoids(PG,PGI,TX),
leukotrienes, lipoxins.

31. MONO UNSATURATED FA
 Contains one double bond.
Eg:
• C16 palmitoleic acid
• C18 oleic acid

32. PUFA
 Contain 2 or more double bonds
 Examples-
linoleic acid 18C, 2 double bond, ω6 family.
linolenic acid18C, 3 double bond, ω3 family.
arachidonic acid 20C, 4 double bond, ω6 family.
 Nutritionally essential, hence called ESSENTIAL
FATTY ACIDS.
 PG,PGI,TX are derived from arachidonic acid .
 Docosa hexa enoic acid (DHA) present in fish oil. High
concentration found in retina, cerebral cortex, sperms.

34. Essential fatty acids
DEFINITION: These fatty acids cannot be
synthesized by the body and therefore should be
supplied in the diet.
found in vegetable oils fish oils.
EX: Linoleic acid, linolenic acid , arachidonic acid
FUNCTIONS:
➢ Synthesis of eicosanoids.
➢ PUFA -EFA are required for membrane structure
and function.
Increase fluidity of membrane because of
cis configuration

35. ➢ Esterification of cholesterol & excretion or
transport of cholesterol.
They are hypocholesterolemic and hence anti-
atherogenic effect.
➢The omega-3 FA decrease VLDL and LDL.
lowers the risk of cardiovascular diseases
➢Prevents dermatitis, eczema in children.
➢Excess of PUFA may lead to production of free
radicals.

36. Clinical significance
 Deficiency of EFA causes acanthocytosis,
hyperkeratosis, acrodermatitis,
hypercholesterolemia.
 EFA deficiency is linked with heart attacks,
insulin resistance, obesity.

38. PROPERTIES OF FATTY ACIDS
HYDROGENATION:
 Hydrogenation of double bonds.
 Unsaturated→ saturated fatty acids
Ex: Linolenic→linoleic→oleic→stearic.
HALOGENATION:
 When treated with halogens, unsaturated fatty acid take up 2
halogen atom at double bond to form Halogenated Derivative
of fatty acid.
Ex: oleic acid +I2→ Di-iodo oleic acid.
 Index of unsaturation.

39. MELTING POINT :at 25oC Short & medium chain FA –
liquids
Long chain FA—solids
UNSATURATED FA→ LOWER MELTING POINT
compared to SATURATED FA.
SALT FORMATION:
 SATURATED & UNSATURATED FA form salts with
alkali.
 Sodium ,potassium, Calcium ,Magnesium salts of long
chain FA called→ SOAPS.

40. ESTER FORMATION:
 SATURATED & UNSATURATED FA form ester with
alcohols.
OXIDATION OF FA:
 All FA undergo beta oxidation in body to give energy .

41. NEUTRAL FATS/TAG
 Simple and mixed TAG
 Simple- Tripalmitin, Triolein
 Mixed – 1,3 dipalmitoyl-2-olein
Physical properties of TAG
 -HYDROPHOBIC
 -oils are liquids at room temp
 -fats are solids at room temp
 Storage form of energy
 in 70kg man 11kg is TAG

42. Properties of fats
1. Melting point-
TAG of saturated FA → have higher
melting points and
TAG of unsaturated FA→ have lower
melting point.
2. Solubility – fats are insoluble in water but soluble
in nonpolar organic fat solvents.

43. Micelle
Emulsification
• on adding emulsifying
agents each fat droplet gets
covered on its surface by
thin layer of the emulsifying
agent whose polar group are
oriented towards the
surrounding aqueous phase.
Such molecular aggregates
are called micelles, remain
stable in water to form
aqueous emulsion of fat.

44. 4. Hydrolysis - Lipases
5. Saponification- alkaline hydrolysis of fats resulting in
soap formation is known as Saponification.
 Saponification number – defined as the number of
milligram of KOH required to saponify 1gm of fat.
 Saponification number is inversely proportional to the
chain length.
 Its an indication of molecular weight of fat.
Example: Human fat-194-198
Butter 210-230
Coconut oil 252-262

45. 6.IODINE NUMBER :of a fat is defined as the
number of grams of iodine taken up by 100
grams of fat.
 It is the index of the degree of unsaturation & is
directly proportional to the content of the
unsaturated fatty acids.
 Higher the iodine number, higher is the degree of
unsaturation.
Example: Coconut oil 7-10
Butter 28
Sunflower oil 145-150

46. 7. RANCIDITY
Appearance of unpleasant smell and taste of fats
and oils on standing.
it occurs on exposure to air,
moisture,
warm temperature,
uv light.
a. hydrolytic rancidity.
b. oxidative rancidity.

47.  Hydrolytic rancidity -is due to the partial
hydrolysis of TAG molecules due to traces of
hydrolytic enzymes present in naturally occurring
fats/oils.
 Oxidative rancidity -is the result of partial
oxidation of unsaturated FA with resultant
formation of epoxides and peroxides of small
molecular weight FA by peroxides and free
radicals.
short chain aldehydes and ketones are formed.

48. Waxes
 Are esters of higher fatty acids(FA) with higher monohydroxy
aliphatic alcohols. They have very long straight chains.
eg beewax, lanolin(bootwax).

49. PHOSPHOLIPID

50. GLYCEROPHOSPHOLIPIDS
 Phosphatidic acid.
 Phosphatidyl choline(lecithin).
 Phosphatidyl ethanolamine(cephalin).
 Phosphatidyl serine.
 Phosphatidyl inositol.
 Phoshatidyl glycerol(cardiolipin).
 Plasmalogens.

52. Phosphatidic acid
 It is made up of one glycerol to which two FA
residues are esterified to carbon atoms 1 and
2 and the third hydroxyl group is esterified
to a phosphoric acid.

53. Lecithin
 They have a nitrogenous base choline bound
to the phosophate group.
 Predominant glycerophospholipid in cell
membrane

54. FUNCTIONS
 Acts as storage for body's choline reserve
 Helps cholesterol dissolve in bile
 Emulsification of lipids & its absorption in GI
tract
 The lecithin-sphingomyelin ratio of the
amniotic fluid is a index of fetal maturity.
 Estrification of cholesterol
 As part of lipoprotein it helps transport of fat
 Provides arachidonic acid for Eicosanoid
synthesis

55.  A1 – Acylglycerophosphoryl choline + FA
 A2 – lysoleithin + FA
 C – 1,2 diacylglycerol + PhosphorylCholine
 D – phosphaitdic acid + Choline
CHOLIN
Action of Phospholipase

56. LUNG SURFACTANT
 CONSTITUENTS
 Dipalmitoyl lecithin - Cholesterol
 Surfactant protein A, B, C - Phosphotidyl glycerol
 Produced by – Alveolar epithelial cells
 It decreases the surface tension of aqueous layer of
the lung & prevents collapse of lung alveoli
 Fetal life before 28wks Sphingomylein
 Matured fetus more Lecithin
 The lecithin –Sphingomylein (L/S) ratio of amniotic
fluid – INDEX OF FETAL MATURITY

57. RESPIRATORY DISTRESS SYNDROME
 Defect in synthesis of DIPALMITOYL
LECITHIN
 Premature infants – higher incidence

58. Cephalin
 They have nitrogenous base ethanolamine
bound to the phosphate group.
 It is found in biomembranes.

59. Phosphatidyl serine
 Here amino acid serine is esterified to the
phosphate residue.
 They occur in brain, erythrocytes.

60. Phosphatidyl inositol
 Here phosphatidic acid is esterified to
inositol.
 Phosphatidyl inositol biphosphate or PIP-2
is present in biomembranes.
 This compound plays a vital role in the
mediation of harmone action on
biomembranes.

61. SPHINGOPHOSPHOLIPIDS
 These phospholipids carry sphingosine(is a
nitrogenous dihydroxy, C 18 alcohol).

62.  Sphingomyelin occurs in brain, liver, cardiac
muscle.
 Sphingomyelins are located in the nerve cell
membranes. They account for 25% of lipids in
myelin sheath.
 Acts as an emulsifying agent and detergent.
 The ratio of proportion of lecithin and
sphingomyelin is important in biological
fluids like bile amniotic fluid etc.

63. FUNCTIONS OF PHOSPHOLIPID
 Component of
cell membrane –
regulate cell
permeability
 Amphipathic in
nature

64. MICELLAR FORMATIO
 Phospholipids in water – micelle formation
 Involved in solublization of lipids in
aqueous medium & help in digestion &
absorption of Lipids

65. LIPOSOMES
 Sonication of mixture of Phospholipid & cholesterol
 Microscopic spherical vesicles
 Drugs, proteins, enzymes, genes – carried to target
organs
 Important application in Cancer chemotherapy, Gene
therapy, Vaccines, Diagnostic imaging

66.  Couple oxidative phosphorylation – ETC
 Source of Arachidonic acid – precursor of
Eicosanoids
 Second mesanger – Phosphatidyl Inositol
 Role in blood coagulation
 Surfactant
 Transport of Cholesterol

67. GLYCOLIPIDS
 These are carbohydrate lipid complexes. Each
molecule contains sphingosine, a fatty acid
molecule and a carbohydrate molecule.
 CEREBROIDES
 GLOBOSIDES
 GANGLIOSIDES
Carbohydra
te

68. Lipoproteins
 Macromolecular complex of lipid & protein
that transport insoluble lipids through the
blood b/w different organs & tissues
 Consists of
 lipid core – TAG & Cholesterol esters
 Single layer of Amphiphatic
phospholipids & free cholesterol with
some proteins

69.  The protein part of the lipoprotein is called as
apolipoprotein
4 major types
 Apo A , Apo B, Apo C, Apo E
 3 subgroups I, II, III

70. Classification of lipoproteins
 Chylomicrons
 VLDL or pre beta lipoproteins.
 LDL or beta lipoproteins.
 HDL or alpha lipoproteins.

72. Chylomicrons
 Transport form of dietary triglycerides to be
delivered to adipose tissue for storage and to
muscle & heart for their energy needs.
 Synthesized in the Intestine
 The TAG, cholesterol ester and phospholipid
molecules along with apoproteins B48, apo-
C are incorporated into chylomicrons.
 The half life of chylomicrons in blood is
about 1 hr.

74. VLDL
 Major carriers of endogenous TG from Liver
to peripheral tissues
 Synthesized in the liver
 Contains apo-B-100, C-II, apo-E
 Half life 1-3hrs.

75. LDL
 Cholesterol rich lipoproteins containing only
apo-B-100.
 About 75% of plasma cholesterol is incorporated
into LDL particles.
 Most of the LDL is derived from VLDL
 Half life 2 days.
 LDL transports cholesterol from liver to the
peripheral tissues.
 LDL concentration in blood has a positive co-
relation with the incidence of cardiovascular disease.
 BAD cholesterol.

77. HDL
 Main transport form of cholesterol from
peripheral tissues to liver.
 It is anti-atherogenic.
 HDL<35mg/dl increase risk of CVD.
 HDL>60mg/dl protects from CVD.

78. LIPOPROTEIN a
 Variant of LDL
 Synthesized in Liver
 Composition – same as LDL but ApoB 100 is
linked by disulphide bond to Apoa
(Glycoprotein)
 Interferes with fibrinolysis
 Plasma levels <0.3gm/dL
 Elevated levels --- increased risk of CVD

79. STEROLS
 Sterols are structural lipids present in the
membrane of most of the eukaryotic cells
 Cholesterol is a major animal Sterol

80. CHOLESTEROL
 It is a derived lipid. Consists of sterol
nucleus
 Total cholesterol
<200mg/dL
 Structure- CPPP
 Most of it is as
Cholesterol ester

81. CH3
CH3
HO
Steroid ring
1
2
3 4
5
6 7
8
9
10
11
12
13
14 15
16
17
18
19
A B
C D
CYCLOPENTANOPERHYDROPHENANTHRENE

83. Functions
1) Structural component of cell membranes-
influences membrane permeability
2) Insulator for nerve fibers
3) Precursor for synthesis of biologically
important products
 Steroid hormones
 Glucocorticoids, Mineralocorticoids,
Androgens, Estrogen, Progesterone
 Bile acids – acts as emulsifying agents, helps
in digestion & absorption of dietary fats
 Vitamine D – regulates Calcium &
Phosphorus metabolism

84. 4) Essential ingredient of lipoproteins.
5) Fatty acids are transported to liver as
cholesterol esters.
5) The level of cholesterol in blood is of primary
importance due to its role in the development
of atherosclerosis.

85. Bile acids:
 They are produced from oxidation of
cholesterol in the liver producing cholic
and chenodeoxycholic acids that are
conjugated with glycine or taurine to
produce glycocholic,
glycochenodeoxycholic, taurocholic and
taurochenodeoxycholic acids. They
react with sodium or potassium to
produce sodium or potassium bile salts.

86. Function is as follows:
1.Emulsification of lipids during digestion.
2.Help in digestion of the other foodstuffs.
3.Activation of pancreatic lipase.
4.Help digestion and absorption of fat-
soluble vitamins.
5.Solubilizing cholesterol in bile and prevent
gall stone formation.
6.Choleretic action (stimulate their own
secretion).

87. EICOSANOIDS
 Biologically active molecules
Types
 Prostaglandins (PG)
 Prostacyclins (PI)
 Thrombaxanes (TX)
 Leukotrines (LT)

88. Biosynthesis of Eicosanoids
PHOSPHOLIPASE A2
ATTACKS MEMBRANE PHOSPHOLIPID
RELEASE OF ARACHADONIC ACID
CYCLOOXYGENASE lipoxygenase
PG’S TX LEUKOTRINES

89. ARACHADONIC ACID
Cyclooxygenase Lipooxygenase
PGG2 5-Hydroxyecosatetraenoic acid
Peroxidase LTA4
PGH2 LTB4 LTC4 LTD4 LTE4
TXA2 PGE2 PGF2a PGI2 PGD2

90. BIOLOGICAL ACTIONS & CLINICAL SIGNIFICANCE
1. Inflammation
2. Regulation of BP
3. Effect on platelet aggregation
4. Effect on Uterus
5. Effect on Gastrointestinal system
6. Effect on Respiratory system
7. Effect on Metabolism
8. Effect on Renal system

91.  Inflammation
 Eicosanoids are mediators of
inflammation
 Effect on platelet aggregation
 Thrombaxanes TXA2 causes platelet
aggregation
 Prostacyclins PGI2 inhibit Platelet
aggregation

92.  Effect on Respiratory system
 PGE -- Bronchodilator
 PGF – Bronchoconstrictor
 Effect on Metabolism
 PGE – decreases lipolysis, increases
glycogenesis
 Effect on Renal system
 PGE – increases glomerular filtration rate

93.  Effect on Uterus
 Stimulates uterine contraction
 Effect on GI system
 Increases intestinal motility and inhibit
gastric acid secretion

94. TYPE SITE FUNCTION
PGE2 MOST TISSUES VASODILATION , SMOOTH MUSCLE
RELAXATION
INDUCE LABOUR
PGF2a MOST TISSUES VASOCONSTRICTION, SMOOTH MUSCLE
CONSTRICTION
BRONCHOCONSTRICTION , STIMULATES
UTERINE CONTRACTIONS
PGI2 ENDOTHELIUM
OF VESSELS
VASODILATION
INHIBITS PLATLET AGGREGATION
TXA2 PLATELETS PLATELET AGGREGATION,
VASOCONSTRICTION, SMOOTH MUSCLE
CONSTRICTION, BRONCHOCONSTRICTION
LT LEUCOCYTES,
PLATELETS
VASOCONSTRICTION,
BRONCHOCONSTRICTION , INCREASE
CELLULAR PERMEABILITY

95. Spingolipidosis or lipid storage
disorders

96. Dr Anurag Yadav
MBBS, MD
Assistant Professor
Department of Biochemistry
Instagram page –biochem365
Email: dranurag.y.m@gmail.com