lecture slides for chemistry of lipids

2. Lipids are a class of heterogenous compounds which are
relatively insoluble in water and soluble in nonpolar
solvents.
 Chemically: either esters of fatty acids
or substances capable of forming such
esters

3. BIOMEDICAL IMPORTANCE
1. Stored as a source of energy in the body.
Lipid (TGL)
Droplets In
Adipose tissue

4. 2. Structural components of biomembranes.

5. 3. Thermal Insulator :
Provides insulation against changes in external
temperature.

6. 4. Lipids act as electric insulators in neurons.

7. 5. Act as metabolic regulators (steroid hormones and
prostaglandins).
6. Act as surfactants and prevents collapse of lungs during
expiration.
7. Lipids are used as detergents.
8. Lipids used in emulsification and intestinal absorption of
non polar nutrients like fatty acids and fat soluble
vitamins.
9. Associated with diseases such as atherosclerosis,
diabetes mellitus and obesity.
10. Gives shape and contour to the body.

9. LIPIDS
1. Simple 2. Compound Lipids 3. Derived Lipids
Lipids

10. 1. Simple Lipids
Esters of fatty acids with various alcohols.
a. Fats :esters of fatty acids with glycerol.
eg: triglycerides.
b. Waxes: esters of fatty acids with higher
molecular weight monohydric alcohols.
eg: beeswax
Glycerol

11. 2. Compound
Lipids
Esters of fatty acids with various alcohols along
with an additional group.
Simple lipid + Additional group = Compound Lipids
a. Phospholipids:
b. Glycolipids:
c. Other Complex Lipids:

12. COMPOUND LIPIDS
Esters of fatty acids with various alcohols along
With an additional group.
Phospholipids Glycolipids Others
Glycerphospholipids
-Phosphatidyl choline Cerebrosides Lipoproteins
- Phosphatidyl ethanolamine
Gangliosides Aminolipids
- Phosphatidyl serine
- Phosphatidyl inositol Globosides
- Cardiolipin
- Plasmalogens
Sphingophospholipids

13. 3. Derived Lipids
Lipid molecules derived from simple/compound lipids
on their hydrolysis
Fatty acids
Eicosanoides
Steroids
Sterols
Cholesterol
Bile acids
Vitamins (A,D,E,K)
Ketone Bodies

14. SIMPLE LIPIDS
NAME ALCOHOL ACID EXAMPLE
Fats Glycerol Fatty acid Triglycerides
Waxes Aliphatic / Fatty acid Bees wax
Aromatic
alcohol

15. Phospho lipids

16. NAME ALCOHOL ACID Po4 ADDITIONAL
GROUP
GLYCERO PHOSPHO LIPIDS
Phosphatidyl Glycerol Fatty acid Po4 Choline
choline
(lecithin)
Phosphatidyl Glycerol Fatty acid PO4 Ethanolamine
ethanolamine
(cephalin)
Phosphatidyl Glycerol Fatty acid PO4 Serine
serine
Phosphatidyl Glycerol Fatty acid PO4 Myoinositol
inositol
Cardiolipin Glycerol Fatty acid PO4 Phosphatidyl
glycerol
Plasmologens Glycerol Fatty acid (ether PO4 Ethanolamine
link at C1)
SPHINGO PHOSPHO LIPIDS

17. Glycolipids
NAME ALCOHOL ACID GLYCOSYL ADDITIONAL
RESIDUE GROUP
Cerebrosides Sphingosine Fatty acid Galactose/
(cerebronic Glucose
acid)
Gangliosides Sphingosine Fatty acid Glucose Sialic acid
Globosides Sphingosine Fatty acid Glucose +
Galactose
Sulphatides Sphingosine Fatty acid Galactose SO3
Note:
Ceramide: Sphingosine + Fatty acid Slide 51

19. CLASSIFICATION OF FATTY ACIDS
Based on ‘R’ group
1. Small / Medium / Long Chain Fatty Acids
2. Odd / Even Chain Fatty Acids
3. Saturated / Unsaturated Fatty Acids
Nutritionally
Essential / Non-Essential Fatty Acids

20. 1. Small / Medium / Long Chain Fatty Acids
Small chain Fatty acids : 2 – 4 carbons
Medium chain Fatty acids : 6 – 14 carbons
Long chain Fatty acids : more than 16 carbons

21. 2. Odd / Even Chain Fatty Acids
12 11 10 9 8 7 6 5 4 3 2 1
13 12 11 10 9 8 7 6 5 4 3 2 1

22. Saturated Fatty Acids
a) Even chain fatty acid
eg., Palmitic acid
Stearic acid
a) Odd chain fatty acid
eg., Propionic acid
Unsaturated Fatty Acids
a) Mono unsaturated fatty acid (MUFA)
eg., Oleic acid
b) Poly unsaturated fatty acid (PUFA)
eg., Linoleic acid, Linoleinic acid, Arachidonic acid
a) Eicosanoids

23. USES / FUNCTIONS OF PUFA
Major components of membrane lipids
Contributes to the fluidity of membranes
Used for Prostaglandin synthesis
Decreases the incidence of Atherosclerosis,
Coronary Artery Diseases

24. Saturated fatty acids: rich in storage lipids (adipose tissue)
Unsaturated fatty acids: rich in membrane lipids
(to increase fluidity)

25. Based on Nutrition
Essential
Non essential

26. Essential Fatty Acids
Fatty acids that can not be synthesized by body & has to
be supplied by diet
Ex: Linoleic acid
Linolenic acid
Arachidonic acid
Functions:
Structural composition of Brain & Nervous system
Precursor for Eicosanoid synthesis
Prevents atherosclerosis
Prevents skin lesions

28. 12 11 10 9 8 7 6 5 4 3 2 1
ω ε δ γ β α
Two types
1. ω – type
2. N - type

29. Indicating Number & Position of Double Bond
18:1,9
Δ9 18:1
ω3, ω6, ω9
Fatty Acids
ω9,C18:1

30. Melting Point :
• Temperature at which fats are converted from solid
state to liquid state.
• Saturated acids have high melting point than
unsaturated acids
• Increases with increase in hydrocarbon chain length
Solubility:
Decreases with increasing chain length
Increases with temperature.
Unsaturated fatty acids exhibit cis-trans isomerism

31. GEOMETRIC ISOMERISM OF OLEIC AND ELAIDIC ACIDS
Natural Fatty acids – ‘cis’ form

32. 1. Salt Formation
2. Esterification
3. Hydrogenation
4. Halogenation
5. Hydrolysis
6. Oxidation

33. 1. SALT FORMATION
R – COOH + NaCl R – COONa + HCl
Fatty acids react with alkalies to form Salts of fatty acids
Na+ or K+ salts of fatty acids : Soaps

34. 2. ESTERIFICATION
+ +
Most of the fatty acids of body are in esterified form

35. 3. HYDROGENATION
(hardening)
CH3 – CH2 – CH – CH – CH2 – COOH
–
H2
CH3 – CH2 – CH2 – CH2 – CH2 – COOH
Unsaturated FA converted to Saturated FA
Used to synthesize Vanaspathi & Margaraine
Trans Fatty acids are formed

36. 4. HALOGENATION
CH3 – CH2 – CH – CH – CH2 – COOH
–
I2
CH3 – CH2 – CH – CH – CH2 – COOH
I I
The amount of halogen taken by a fatty acid depends on
No of double bonds
Degree of unsaturation

37. TAG undergoes stepwise hydrolysis of its ester bonds to
form Glycerol & Free Fatty acids
Lipases
Digestion of Fats in GIT
Mobilisation of TGL from Adipose tissue

39. GLYCERO PHOSPHOLIPIDS
Phosphatidic Acid

40. Choline
Phosphatidyl
Phosphatidic acid
Ethanolamine
Serine
Inositol
Phosphatidyl
Glycerol

41. Plasmalogens

42. Phosphatidyl Choline (LECITHIN)
Choline
Phosphatidic acid + Choline
Lecithin acts as lung surfactant
Most abundant phospholipid of biomembranes

43. Phosphatidyl Choline (LECITHIN)
Dipalmitoyl Lecithin – Lung surfactant.
Synthesized by Alveolar type - II cells.
Rich in alveolar fluid lining the alveoli
Reduces surface tension of alveolar fluid & prevents collapse
during expiration
Deficiency in premature infants leads to collapse
– Respiratory Distress syndrome

44. SITE OF ACTION OF PHOSPHOLIPASES
Phospholipase A1
Phospholipase A2
Phospholipase D
Phospholipase C

45. SPHINGO PHOSPHOLIPIDS
 Sphingosine – alcohol moiety
 Commonly found in nerve tissues

46. SPHINGOPHOSPHOLIPIDS Sphingomyelin
Sphingomyelin

47. SPHINGOPHOSPHOLIPIDS

48. 1. Structural components of cell membrane.
2. Enable enzyme action.(mitochondrial enzyme
system).
3. Required for blood coagulation (prothrombin to
thrombin, activation of factor 8 by factor 9).
4. Transports lipids from intestine and liver.
5. Choline acts as a lipotropic agent since it prevents
the formation of fatty liver.
6. Phospholipids of myelin sheath provides insulation
around nerve fibers.

49. COMPOUND LIPIDS
Esters of fatty acids with various alcohols along
With an additional group.
Phospholipids Glycolipids Others
Glycerphospholipids Cerebrosides Aminolipids
Sphingophospholipids Gangliosides Lipoproteins
Sulfatides
Globosides

50. o Lipids containing carbohydrate moiety - Glycolipids
o Alcoholic component – Sphingosine
o Ceramide – Common group of all Glycolipids
o Occur in brain, spinal cords and other tissues.
o Predominant in outer leaflet of biomembranes

51. GANGLIOSIDES (Ceramide + Oligosaccharide + Sialic acid)
GM1 = Ganglioside with monosialic acid
GD2 = Ganglioside with two sialic acid residues
GT3 = Ganglioside with three sialic acid residues
Sialic acid = N-Acetyl Neuraminic acid (NANA)

52. 1. Cerebrosides
2. Sulfatides
Types of
Glycolipids
3. Globosides
4. Gangliosides

53. STEROIDS
Lipids containing Cyclo Pentano Perhydro Phenanthrene
(CPPP) ring
18
12 17
11 16
13
C D
1 19
9 14 15
2
10 8
A B
3 7
5
4 6

54. STEROLS
Steroids containing alcoholic group - Sterols
Plant Sterols : Ergosterol, Stigmasterol, Sitosterol
Animal Sterols : Cholesterol

55. CHOLESTEROL
Chemistry:
 Has Steroid Nucleus
 OH group at 3rd position
 Double bond between 5th & 6th carbons
 8-Carbon containing side chain at 17th position.
17
3 5
6

56. CHOLESTEROL
Chemical Properties
1. Undergoes rapid oxidation to form cholestenones.
2. Hydroxyl group forms esters with acids to form
Cholesterol Esters (cholesterol acetate,palmitate
and propionates)
3. Presence of double bond gives hydrogenation
reactions (similar to unsaturated fatty acids).
4. Colour reactions:
LIEBERMANN BURCHARD,
SALKOWSKY,
ZAKS.

57. CHOLESTEROL
Biomedical Importance
Structural role – Biomembranes, Lipoproteins
Occur in large amounts in brain and nerve tissues.
Act as insulator against nerve impulses which discharge
electric charges.
Biomolecules synthesized from cholesterol
Bile acids
Vitamin D
Steroid hormones :
Androgens, Estrogens, Progesterone,
Aldosterone etc

58. BILE ACIDS
 Cholesterol is eliminated from the body as bile
acids through bile.
 Help in digestion & absorption of fats and fat
soluble vitamins
 Synthesised in liver, stored in gall bladder and act
in intestine

59. BILE ACIDS
Primary Bile Acids Secondary Bile Acids
Synthesised from Cholesterol Synthesised from primary
in Hepatocytes Bile acids in Intestine
Ex: Ex:
Cholic acid Deoxycholic acid
Chenodeoxycholic acid Lithocholic acid

60. EICOSANOIDES
20 CARBON CONTAINING FATTY ACIDS GENERATED FROM
ARACHIDONIC ACID
• Discovered in prostate gland secretions
• Synthesized in all tissues
• Acts as local hormones
• Function in even low concentrations

61. EICOSANOIDES
COX LOX
Prostanoides Leukotrienes Lipoxins
Prostaglandins
Thromboxanes
Prostacyclins

62. Prostaglandin
O
OH
Protanoic acid – Precursor molecule
Cyclopentane ring substituted with hydroxyl / keto groups
Based on difference in these substituted groups, PGs classified as
PG-A, PG-B, PG-C, PG-D, PG-E, PG-F, PG-H
Based on number of double bonds, PGs have three series
PG1 – One double bond
PG2 – 2 double bonds PG2 - most common series
PG3 – 3 double bonds

63. Functions of prostaglandin
 Smooth muscle contraction/relaxation
 Vaso constriction
 Broncho dilation (PGE2)
 Uterine contraction (PGF2)
 Capillary permeability
 Inflammation and pain
 Platelet aggregation

64. Thromboxanes
Unsaturated, substituted C-20 fatty acids with an oxane
ring.
Occur in the cells of many tissues like blood platelets,
lung, brain etc.

65. PGI2 Vs TXA2
Prostacyclin (PGI2) Thromboxane (TXA2)
Produced mainly from Produced mainly from
vascular endothelium platelets
Smooth muscle relaxation Smooth muscle contraction
Inhibits platelet aggregation Stimulates platelet
aggregation

66. Leukotrienes, Lipoxins

67. Lipids having both hydrophobic and hydrophilic groups
Ex:
Phospholipids
Cholesterol
Glycolipids

68. Lipid Aggregates in Aqueous
Compartment
Micelle Formation

69. Bilayer Formation

70. Liposome Formation
Prepared by sonication of amphipathic lipids

71. Liposomes
 Liposomes (microscopic spherical vesicles) when
mixed with water under special condition, the
phospholipids arrange themselves to form a bilayer
membrane enclosing water-filled central core
 Impermeable to polar materials and helps maintain
the composition of the enclosed aqueous fluid.

72. Uses of Liposomes
To deliver
drugs
proteins
enzymes
genes

73. Drug release

74. Are spherical complexes made up of lipids and
proteins .

75. STRUCTURE
Inner Core Outer Wall
Nonpolar lipids Amphipathic lipids & Proteins.
TAG, Cholesterol esters Phospholipids, Cholesterol

77. Lipoproteins = lipids + proteins
Apoproteins
Al All Alll
B48 B100
Cl Cll
D
E

78. Functions of Apoproteins:
1. Act as structural components of lipoproteins.
2. Recognize the cell membrane surface receptors,.
3. Activate enzymes involved in lipoprotein
metabolism .

79. TYPES OF LIPOPROTEINS
Based on density (lipid:protein ratio)
1. Chylomicrons
2 . Very Low Density Lipoproteins (VLDL)
3 . Low Density Lipoproteins (LDL)
4 . High Density Lipoproteins (HDL)

80. Ultracentrifugation Electrophoresis

81. Ultracentrifugation
Chylomicrons
VLDL
IDL
LDL
HDL

82. Electrophoresis
+ve +ve
α -lipoprotein
HDL
VLDL Pre β
IDL
LDL β Lp
Chylomicron
-ve -ve

84. Lipoprotein Apo lipoprotein Functions
(trnspt Chol.,)
Chylomicron Apo AI, AI, B48, CI, CII, CIII, E Intestine to
tissue
VLDL B100, CI, CII, CIII, E Liver to tissue
LDL B100 Liver to tissue
IDL B100 Liver to tissue
HDL Apo AI, AII, AIV, CI, CII, CIII, E Tissue to liver

85. RANCIDITY OF FATS
Formation of unpleasant odour and taste in stored lipids is
called as Rancidity.
• Denotes the deterioration of lipids & becomes unsuitable
for consumption
• Occurs when exposed to air, moisture or bacteria
• TGL with unsaturated fatty acids more susceptible for
rancidity

86. Types of Rancidity
1. Hydrolytic Rancidity:
Partial hydrolysis of TGL by the bacterial enzymes
2. Oxidative Rancidity:
Partial oxidation of fats leading to formation of peroxides &
their corresponding aldehydes
Prevented by adding Anti-oxidants

87. LIPID PEROXIDATION
Free Radicals
Lipids Lipid peroxides + Free Radicals
O2
Lipid peroxidation - generates of free radicals
(ROO*,RO*,OH*)
Free radicals : Have unpaired electrons in their outer orbits
They oxidize & damage any biomolecules
Peroxidation : damages tissues in vivo,
(free radicals) causes of cancer, Inflammatory diseases,
atherosclerosis, and aging etc.

88. Three Stages of Peroxidation
1. Initiation
2. Propagation
3. Termination

89.  Substances which control and prevent free radicals.
Types
1. Preventive Antioxidants:
Decrease the rate of chain initiation step.
Ex: Catalase, Metal ion chelators such as EDTA
2. Chain Breaking Antioxidants:
Interfere with chain propagation step.
Ex : Superoxide dismutase(SOD), Vitamin E
Uses
 Protects biomembrane from the effect of free radicals
 Added in fats for storage purpose
 Protects the body from multiple diseases

90. Tests to check the purity of Simple Lipids
1. Iodine Number
2. Saponification Number
3. Reichert Miesel Number
4. Acid Number
5. Acetyl number

91. Defined as the number of grams of iodine taken up
by 100gms of fat.
Index of degree of unsaturation
Iodine Number degree of unsaturation
‫ﻌ‬
Uses:
To detect the degree of unsaturation
To detect adulteration

92. IODINE NUMBER
Fats / Oils Iodine No
Coconut oil 7-10
Butter 25-28
Groundnut oil 85-100
Sunflower oil 125-135

93. SAPONIFICATION NUMBER
Defined as the number of milligrams (mgs) of potassium
Hydroxide (KOH) required to saponify one gram of fat.
Index of molecular weight / chain length fatty acids
1
Saponification Number ‫ﻌ‬
molecular weight (or) chain length
Uses:
To detect molecular weight / chain length fatty acids
To detect adulteration

94. ACETYL NUMBER
Defined as the Milligrams of KOH required to combine
with the acetic acid liberated by the saponification of
1 gm of acetylated fat.
Indicator of number of hydroxyl groups
Castor oil has acetyl value of 146 to 150 indicating the
presence of sufficient hydroxylated acids.
Butter has an acetyl value of 1.9 to 8.6 ,indicating the
presence of very small amounts of hydroxylated acids.

95. REICHERT-MEISSL NUMBER
Defined as the millimeters of 0.1N alkali required to
neutralize the volatile acids obtained from 5 gm of fat .
Butter fat has a Reichert-Meissl number of 26-33
whereas the number for lard is 0.6.

96. ACID NUMBER
Defined as the Milligrams of KOH required to neutralize
the free fatty acids present in 1gm of fat.
It is of value in determining rancidity due to
free fatty acids.