Detailed chapter on Medical Lipid chemistry under different heading. The content is designed keeping the course in the view - MBBS, BDS, BPT, Nursing, BSc, MSc etc

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

2. Constituents of diet
• Carbohydrates
• Lipids
• Proteins
• Vitamins
• Minerals
• water

3. Lipid Chemistry
• Why do we need to study lipid chemistry
• Definition
• Functions
• classification

4. Give some examples for Lipids
• Fats
• Fatty acids
• Cholesterol
• Waxes
• Phospholipids
• Glycoproteins
• Lipoproteins

5. What are Lipids?
are a heterogeneous group of compounds,
which are relatively insoluble in water and
soluble in nonpolar solvents such as ether and
chloroform.
examples

6. Why do we need to study lipid
chemistry

7. Clinical implication
• Excessive fat deposits cause Obesity.
• Truncal obesity is a risk factor for heart attack

8. Clinical implication
• Abnormality in cholesterol and lipoprotein
metabolism leads to the atherosclerosis and
cardiovascular diseases.

9. Clinical implication
• In diabetes mellitus, the metabolism of fatty
acids and lipoproteins are deranged, leading
to the ketosis.

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. Occurrence of Lipids?
• Widely distributed in plants and animals.
• Plants: nuts, seeds and oils
• The Nervous system of Animals: cholesterol,
phospholipids and glycolipids
• Blood: contains lipoproteins
15

16. Occurrence of Lipids?
• Fat depots (large amount
of fats):
– Subcutaneous tissues
– Mesenteric tissues
– Fatty tissues around the kidney
– Yellow bone marrow
• Food sources:
– Milk, Egg, Meat, Liver
– Fish oils, nuts, seeds and oils
16

17. Following diseases are associated with abnormal
chemistry or metabolism of lipids-
Obesity
Atherosclerosis
Diabetes Mellitus
Hyperlipoproteinemia
Fatty liver
Lipid storage diseases
Dr Anurag Yadav, 5/27/2021

18. Classification of Lipids
Based on chemical composition classified into 3
groups.
1. Simple lipids:
2. Complex lipids:
3. Precursor and derived lipids:

19. Classification

20. CLASSIFICATION OF LIPIDS.

21. Classification of Lipids
1. Simple lipids:
Esters of fatty acids with various alcohols.
They don’t contain additional group.
Simple lipids = FA + Alcohol
2. Complex lipids:
Esters of fatty acids with alcohol and
containing additional group.
Complex lipids = FA + alcohol + Additional gp
3. Precursor and derived lipids:
are derived from simple and complex lipids by
their hydrolysis.

22. Examples for simple lipids
• Fats
• waxes

23. Examples for complex lipids
• Phospholipids
• Glycolipids
• Sulfolipids
• Lipoproteins etc.

24. Examples for Precursor and derived
lipids
• fatty acids,
• glycerol and other alcohols,
• Sterols and steroid hormones,
• ketone bodies,
• hydrocarbons, and
• lipid-soluble vitamins.

26. 1.Simple lipids
• Esters of fatty acids with various alcohols. They don’t
contain additional group.
Simple lipids = FA + Alcohol
Depending on type of alcohol present simple lipids
are further classified into
• a. Fats are esters of fatty acids with glycerol.
Fats = FA + Glycerol
• b. Waxes are esters of fatty acids with high molecular
weight monohydric alcohol.
FA + higher molecular monohydric alcohol

27. (a). FATS
• Fats are esters of fatty acids with glycerol.
Fats = FA + Glycerol
Examples:
Mono Acyl Glycerol = FA + Glycerol
Di Acyl Glycerol = 2 FA + Glycerol
Tri Acyl Glycerol = 3 FA + Glycerol

28. Tri acyl glycerol
Glycerol
3 R-COOH
3 Fatty acids

30. Tri Acyl Glycerol
There are 2 types based on type of FA present
(i) simple Tri acyl glycerol
(ii) mixed Tri acyl glycerol
(i) simple Triglycerides: in which the three fatty
acid radicals are of the same kind.
Eg:
Tristearin,
triolein,
tripalmitin, etc.

31. (ii) mixed Triglycerides in which the fatty acid
radicals are of more than one kind.
example,
distearo-olein (two radicals of stearic and one
of oleic acid),
dioleo-palmitin ( two of oleic and one of
palmitic), or
stearo-oleo-palmitin (one radical each of
stearic, oleic, and palmitic acids) etc.

32. Functions of Tri acyl glycerol
1. Major dietary constituent
- high energy (calorific) value – 9kcal
- natural fats provide essential fatty acids
and fat soluble vitamins.
2. Major energy reserve of the body
3. Thermal insulator – Fats in the subcutaneous
tissues and around certain organs.
4. Electrical insulator – Fats allow rapid
propagation of depolarization waves along
myelinated nerves.

33. b. Waxes
• Esters of fatty acids with monohydric long chain
alcohols.
Waxes = FA + higher molecular monohydric
alcohol
Example
cetyl palmitate (Palmitic acid + cetyl alcohol)
myricyl palmitate (Palmitic acid +myricyl alcohol)
In animals,
waxes act as lubricants for skin and as a
protective coating.

34. LIPIDS
SIMPLE
LIPIDS
COMPLEX
LIPIDS
PRECURSOR AND
DERIVED LIPIDS
(FA + ALCOHOL)
FATS WAXES
(FA + GLYCEROL) (FA + HIGH MOL.
WEIGHT ALCOHOL)
MAG
DAG
TAG
CETYL PALMITATE
MYRICYL PALMITATE
(FA + ALCOHOL+ ADD. GP) (HYDROLYTIC PRODUCT OF
SIMPLE AND COMPLEX LIPIDS)

35. LIPIDS
SIMPLE
COMPOUND
PHOSPHOLIPIDS
NON-PHOSPHOLIPIDS
DERIVED
OTHERS

36. 2. Complex lipids
Complex lipids = FA + Alcohol + Additional gp
Depending on the type of additional group
present they are further classified into
i. Phospholipids (phosphate as additional gp)
ii. Glycolipids ( carbohydrate as additional gp)
iii. Sulfolipids ( sulfate as additional gp)
iv. Lipoprotein (lipids+proteins) are also
included in this group.

37. Phospholipids
• Phospholipids contain, in addition to fatty acids
and an alcohol, a phosphoric acid residue.
• They invariably carry a nitrogenous base (choline,
ethanolamine, serine etc).
PL = FA + Alcohol + Phosphoric acid+ NB
Based on type of alcohol there are 2 types.
i. Glycerophospholipids contain glycerol as
alcohol
ii. Sphingophospholipids (sphingomyelins) contain
sphingosine as alcohol

39. 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

40. Glycerophospholipids
Glycero PL = 2FA + Glycerol + Phosphate + NB
PHOSPHATIDIC ACID
Examples
(1) Phosphatidylcholine (Lecithin),
(2) phosphatidylethanolamine (Cephalin),
(3) phosphatidylserine,
(4) phosphatidylinositol,and
(5) Diphosphatidylglycerol (cardiolipin)

41. GLYCEROL + + +
2 FATTY ACID PHOSPHORIC ACID NITROGENOUS BASE
PHOSPHATIDIC ACID
-NITROGENOUS BASE
CHOLINE
+
PHOSPHATIDIC ACID
PHOSPHATIDIC ACID
PHOSPHATIDIC ACID
PHOSPHATIDIC ACID
+
+
+
+
ETHANOLAMINE
SERINE
INOSITOL
PHOSPHATIDYL
GLYCEROL
1.PHOSPHATIDYLCHOLINE
2.PHOSPHATIDYLETHANOLAMINE
3. PHOSPHATIDYLSERINE
4.PHOSPHATIDYLINOSITOL
=
=
=
=
=
5.DIPHOSPHATIDYL
GLYCEROL (CARDIULIPIN)
GLYCEROPHOSPHOLIPID
EXAMPLES

42. Examples for glycerophosphplipids
(contd)
Lysophospholipids are glycerophospholipids
containing only one fatty acid radical.
Lyso PL = FA + Glycerol + Phosphate + NB
lysophosphatidic acid
eg,
(6) Lysophosphatidylcholine (lysolecithin)
(7) Lysophosphatidylethanolamine (lysolecithin)

43. GLYCEROL + + +
FATTY ACID PHOSPHORIC ACID NITROGENOUS BASE
LYSOPHOSPHATIDIC ACID
--NITROGENOUS BASE
HO

44. Examples for glycerophosphplipids
(contd)
• (9). Plasmalogens (Ether
Glycerophospholipids)
• resemble phosphatidylethanolamine but
• possess an unsaturated alcohol on the -1
carbon by an ether link.
• In some instances, choline, serine, or inositol
may be substituted for ethanolamine.
• Eg: platelet activating factor

45. GLYCEROL + + +
FATTY ACID PHOSPHORIC ACID
E
PLASMALOGEN
ETHANOLAMINE
UNSATURATED
ALCOHOL

46. ii. Sphingophospholipids
(sphingomyelins)
Are phospholipids containing sphingosine as
alcohol.
SphingoPL = Sphingosine+FA+Phosphate+choline
ceramide

49. Functions of phospholipids
1. Main lipid constituents of plasma membrane.
Phosphatidyl choline is the major PL of
plasma membrane.
• Phosphatidylethanolamine and
phosphatidylserine are also found in cell
membranes.
• Amphipathic nature, has a hydrophilic head
(phosphate + NB) and a long, hydrophobic
tail (fatty acids or derivatives )

50. INTRA CELLULAR EXTRA CELLULAR
PLASMA MEMBRANE
2 LAYERS OF PHOSPHOLIPIDS

51. Functions of phospholipids (contd)
2. Dipalmitoyl lecithin is a very effective
surface-active agent ( surfactant).
• It prevents adherenceof the inner surfaces of
the lungs due to surface tension.
• Its absence from the lungs of premature
infants causes respiratory distress syndrome.

52. Functions of phospholipids (contd)
3. Phosphatidylserine plays a role in apoptosis
(programmed cell death).
4. Phosphatidylinositol 4,5-bisphosphate (PIP2)
helps in signal transduction.
• It is present in cell membrane.
• Upon stimulation by a hormone (oxitocin, TRH
etc) , it is cleaved into diacylglycerol and
inositol trisphosphate, both of which act as
internal signals or second messengers.

53. 5. Cardiolipin is a major lipid of mitochondrial
membrane and is required for mitochondrial
function.
6. Platelet activating factor (PAF – Plasmalogen)
helps in aggregation of platelets.
7. Sphingomyelin is an important component of
myeline sheath of nerve fibers.

54. COMPLEX LIPIDS
PHOSPHOLIPIDS GLYCOLIPIDS LIPOPROTEINS
(FA + ALCOHOL+ PHOS
+ NB)
GLYCEROPL SPHINGOMYELINS
(FA + GLYCEROL
+ PHOS + NB)
(FA + SPHINGOSINE +
PHOS + CHOLINE)
PHOSPHATIDYLCHOLINE
PHOSPHATIDYLETHANOLAMINE
PHOSPHATIDYLSERINE
AG DAG TAG
LYSOPHOSPHATIDYLCHOLINE
LYSOPHOSPHATIDYLETHANOLAMINE
(FA + ALCOHOL+ CARBOH) (LPIDS + PROTEINS)
PLATELET ACTIVATING
FACTOR

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

56. ii. Glycolipids (Glycosphingolipids)
• Are complex lipids containing carbohydrate as
additional group.
• Contain sphingosine, fattyacid and
carbohydrate
Glycolipids = Sphingosine+FA+Carbohydrate
ceramide

59. • Depending on the type of carbohydrate
present glycolipids are classified into
1. Cerebrosides (ceramide+ monosaccharide)
2. Sulfatides (ceramide+ sulfated galactose)
3. Globosides (ceramide+ oligosaccharide)
4. Gangliosides (ceramide+ oligosaccharide+
sialic acid)

60. 1. Cerebroside
are glycolipids containing monosaccharides
(Glucose/Galactose) as carbohydrate group.
Examples
1. Glucocerebroside (ceramide+ glucose)
Found in the plasma membranes of cells in
nonneural tissues.
2. Galactocerebroside (ceramide+ galactose)
found in the plasma membranes of brain and
other nervous tissue.

61. GLUCOCEREBROSIDE

62. GALACTOCEREBROSIDE

63. 2. Sulfatides
• Contain sulfated galactose as carbohydrate
group.
Sulfatides = ceramide+ sulfated galactose
Present in high amounts in myelin sheath.

65. 3.Globosides
• are glycosphingolipids with two or more
sugars (oligosaccharide).
• usually contains D-glucose,D-galactose, or N-
acetyl-D-galactosamine.
Globosides = ceramide+ oligosaccharide

66. GLOBOSIDE

67. 4. Gangliosides
• have oligosaccharide and one or more residues of
“sialic acid” (N-acetylneuraminic acid) as carbohydrate
part.
Gangliosides = ceramide+ oligosaccharide+ sialic acid.
• D-glucose; D-galactose; N-acetyl-D-galactosamine;
N-acetylneuraminic acid (sialic acid).
Examples
Monosialoganglioside (GM)
Disialoganglioside (GD)
Trisialoganglioside (GT)

69. GANGLIOSIDE (GM)

70. COMPLEX LIPIDS
PHOSPHOLIPIDS GLYCOLIPIDS LIPOPROTEINS
CEREBROSIDE GANGLIOSIDE
(FA + SPHINGOSINE
+ MONOSACC)
(FA + SPHINGOSINE +
OLIGOSACC + SIALIC
ACID)
EG:
GLUCOCEREBROSIDE
GALACTOCEREBROSIDE
(FA + SPHINGOSINE+ CARBOH)
MONOSIALOGANGLIOSIDE
DISIALOGANGLIOSIDE
TRISIALOGANGLIOSIDE
(FA + SPHINGOSINE
+ SULFATED GAL)
(FA + SPHINGOSINE
+ OLIGOSACC)
SULFATIDE GLOBOSIDE

71. Functions of Glycolipids
• present in the outer leaflet of plasma
membrane of every tissue of the body
particularly in nervous tissue such as brain
(cell surface carbohydrates).
• where they act as points of recognition
(receptor) for
- extracellular molecules or
- surfaces of neighbouring cells.

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

74. LIPOPROTEINS
• Are Lipid Protein complexes.
Lipoprotein = Lipids + Proteins
• Lipid part is made up of
• triacylglycerols ,
• phospholipids ,
• cholesterol , and
• cholesteryl esters
• The protein moiety of a lipoprotein is known as
an apolipoprotein or apoprotein,

75. Lipoprotein = Lipids Proteins
+
triacylglycerols ,
phospholipids ,
cholesterol , and
cholesteryl esters
apolipoprotein
Apo A,
Apo B-48, Apo B-100
Apo CI,CII,CIII
Apo D
Apo E

76. LIPOPROTEIN MOLECULE

77. Classification of lipoproteins
2 types
• (A) based on density :
4 Classes:
(1) chylomicrons, <0.95
(2) very low density lipoproteins (VLDL), 0.95 –
1.006
(3) low-density lipoproteins (LDL) 1.006 –
1.063, and
(4) high-density lipoproteins (HDL) 1.063 – 1.21

78. (B) Based on electrophoretic mobility:
4 classes
1. α lipoprotein (HDL)
2. β lipoprotein (LDL)
3. Preβ lipoprotein (VLDL)
4. Chylomicrons

79. DENSITY LIPID (MAJOR) APOLIPOPROTEIN
CHYLOMICRONS <0.95 TAG Apo A, B-48, C,E
VLDL 0.95 – 1.006 TAG Apo B-100, C,E
LDL 1.006 – 1.063 CHOL, PL Apo B-100
HDL 1.063 – 1.21 CHOL, PL Apo A, C, D, E

80. Functions of lipoproteins
(carriers of lipids in plasma)
1. Chylomicrons : transport dietary triacylglycerol
from intestine to the extrahepatic tissues.
2. VLDL transports of endogenous triacylglycerol
from liver to the extrahepatic tissues.
3. LDL transports cholesterol from liver to the
extrahepatic tissues.
4. HDL transport cholesterol from the extrahepatic
tissues to liver.

81. 3. Precursors and derived lipids
Are derived from simple and complex lipids by
their hydrolysis.
Other related compounds are also included in
this group.

82. Examples for precursors and derived
lipids
• fatty acids,
• glycerol and other alcohols,
• Sterols and steroid hormones,
• ketone bodies,
• hydrocarbons, and
• lipid-soluble vitamins

83. • Fatty acids - classification
• Essential fatty acids and their functions
• Eicosanoids and their functions
• Cholesterol and its functions and reactions
• Characteristics of fats

84. Fatty acids
Are aliphatic carboxylic acids derived from
hydrolysis of natural fats.
General formula is R- COOH
Where R is hydrocarbon chain

85. Examples (saturated FA)
• Acetic ---------- 2 ------ CH3COOH
• Propionic ----- 3 ------ CH3CH2COOH
• Butyric -------- 4 ------- CH3(CH2)2COOH
• Valeric --------- 5 ------- CH3(CH2)3COOH
• Caproic -------- 6 ------- CH3(CH2)4COOH
• Capric ----------10 ------- CH3(CH2)8COOH
• Lauric ---------12 ------- CH3(CH2)10COOH
• Myristic ------- 14 ------- CH3(CH2)12COOH
• Palmitic ------- 16
• Stearic --------- 18

86. NUMBERING OF CARBON ATOMS

87. ω9

88. FATTY ACIDS - NOMENCLATURE
Common name Systematic name Formula
C2:0 Acetic acid Ethanoic acid CH3COOH
C3:0 Propionic acid Propanoic acid CH3CH2COOH
C4:0 Butyric acid Butanoic acid CH3(CH2)2COOH
C14:0 Myristic acid Tetradecanoic acid CH3(CH2)12COOH
C16:0 Palmitic acid Hexadecanoic acid CH3(CH2)14COOH
C18:0 Stearic acid Octadecanoic acid CH3(CH2)16COOH
C24:0 Lignoceric acid Tetracosanoic acid CH3(CH2)22COOH

89. UNSATURATED FATTY ACIDS - NOMENCLATURE
Common
name
Formula
C16:1(Δ9)
ω7
Palmitoleic
acid
CH3(CH2)5CH=CH(CH2)7COOH
C18:1(Δ9)
ω9
Oleic acid CH3(CH2)7CH=CH(CH2)7COOH
C18:2(Δ9,12)
ω6
Linoleic
acid
CH3(CH2)4CH=CH CH2CH=CH(CH2)7COOH
C18:3(Δ9,12,15)
ω3
Linolenic
acid
CH3CH2CH=CHCH2CH=CHCH2CH=CH(CH2)7COOH
C20:4(Δ5,8,11,14)
ω6
Arachidoni
c acid
CH3(CH2)4CH=CHCH2CH=CHCH2CH=CHCH2CH=CH(CH2)3COOH
C20:5(Δ5,5,11,14,17)
ω3
Timnodoni
c acid
CH3CH2CH=CHCH2CH=CHCH2CH=CHCH2CH=CHCH2CH=CH(CH
2)3COOH

90. Classification of fatty acids
• Based on
A. Total number of carbon atoms
1. Even chain (containing even number of C
atom)
Examples: acetic acid, butyric acid, palmitic acid
stearic acid etc
1. Odd chain (containing even number of C
atom)
Examples: propionic acid, valeric acid etc

91. Classification of fatty acids (contd)
B. Based on Chain length
1. Short chain (containing 2 to 6 C atoms)
Examples: acetic acid, propionic acid, butyric acid,
valeric acid etc.
2. Medium chain (containing 8 to 14 C atoms)
Examples: capric acid, lauric acid, myristic acid etc
3. Long chain (containing 16 to 22 C atoms)
Examples: palmitic stearic, arachidic,oleic acid etc.
4. Very long chain (containing more than 24 C
atoms)
Examples: nervonic acid, cerebronic acid etc

92. C. Depending on nature of hydrocarbon chain
4 types
1. saturated (containing no double bonds) FA.
Examples:
2. unsaturated (containing one or more double
bonds) FA.
They are further classified into
(a) Mono unsaturated fatty acids – contain one
double bond.
Examples:
Classification of fatty acids (contd)

93. Classification of fatty acids(contd)
(b) Poly unsaturated fatty acids(PUFA): contain two
or more double bonds.
Based on number of double bonds present they are
divided into
i. Dienoic fatty acids: contain two double bonds.
Example: linoleic acid
ii. Trienoic fatty acids: contain three double bonds.
Example: linolenic acid
iii. Tetraenoic fatty acids: contain four double
bonds. Example: arachidonic acid.
iv. Pentaenoic fatty acids: contain five double
bonds. Example: timnodonic acid

94. Classification of fatty acids(contd)
3. Branched chain fatty acids
Example: isovaleric acid, isobutyric acid,
tuberculostearic acid etc.
4. Hydroxy fatty acids
Example: cerebronic acid, ricinoleic acid etc.

95. Essential fatty acids (EFA)
• Are fatty acids which cannot be synthesized by
the body and have to be supplied in the diet.
• They are
• Linoleic acid
• Linolenic acid
• Arachidonic acid (can be synthesized from
other EFA)

96. Functions of essential fatty acids (PUFA)
1. Arachidonic acid is the precursor of
prostaglandins.
2. EFAs are constituents of phospholipids
present in plasma membrane.
3. EFAs help to decrease plasma cholesterol
level.
4. (Fatty acids are major source of energy).
5. Deficiency causes skin lesions (phrynoderma)

97. Cholesterol
• Is a derived lipid.
• Contains cyclopentanoperhydrophenanthrene
ring.
• Chemically known as 3- OH Δ5 cholestiene

99. Functions of cholesterol
1. It is an amphipathic molecule, constituent of plasma
membrane and membranes of cellular organelles
2. Helps to maintain permeability and fluidity of plasma
membrane
3. Required for the synthesis of 3 biologically important
group of compounds
(i). Steroid hormones:
Aldosterone, cortisol,
testosterone,
estrogen, progesterone.

100. Functions of cholesterol (contd)
(ii). Bile acids:
cholic acid, chenodeoxy cholic acid –
primary
deoxy cholic acid, lithocholic acid –
secondary
(iii) vitamin D

101. Reactions of cholesterol
1. Esterification
Cholesterol + fatty acid cholesteryl ester
2. Liebermann – Burchard reaction
Chloroform solutions of Cholesterol when
treated with concentrated sulfuric acid and
acetic anhydride develop red, blue and green
color due to the formation of sulfonic acid and
cholestapolyenes.

102. EICOSANOIDS
Are biologically important 20 C compounds formed
from arachidonic acid.
• Prostaglandins(PG) and prostacyclins (PGI) have
the substituted cyclopentane ring at the centre ,
• thromboxanes (TX) have the cyclopentane ring
interrupted with an oxygen atom (oxane ring),
• leukotrienes (LT)and lipoxins (LX) (presence of
three or four conjugated double bonds
respectively)
Physiologically, they are considered to act as local
hormones

103. Prostaglandins
Are 20 C unsaturated compounds carrying
substituted cyclopentane ring.
Types (based on substituted group):
PGD, PGE, PGF,PGG, PGH
Each class is further divided based on number of
double bonds.
Examples:
PGD1,PGD2,PGD3

104. PGE2

105. Functions of eicosanoids
• PGD2 is a potent sleep-promoting substance.
• PGE and PGF stimulate uterine contraction.
So, they are used to induce labor and to
terminate pregnancy.
• PGE is a vasodilator.
• PGF is vasoconstrictor.
• PGD and PGE are proinflammatory agents.

106. Functions of eicosanoids (contd)
• Prostacyclins (PGI2 ) are potent inhibitors of
platelet aggregation.
• Thromboxanes cause vasoconstriction and
platelet aggregation.
• Leukotrienes cause bronchoconstriction and
are potent proinflammatory agents

107. Characterization of fats
1. Saponification number
2. Iodine number
3. Reichter messl number
4. rancidity

108. • Saponification number: is defined as th mg of
KOH required to saponify 1g of fat.
• Each fatty acid residue in the fat uses one
molecule of KOH for being saponified
• It is inversely proportional to molecular weight of
fatty acids present in the fat.
• Example
1. Human fat --- 194-198
2. Butter ----------210 – 230
3. Coconut oil ----253 -262

109. TRI ACYL
GLYCEROL + KOH GLYCEROL + 3R-COOK
SOAP
Saponification reaction
(breakdown)

110. Riechert messel number (value) is defined as the
number of ml of 0.1N NaOH necessary to
neutralise the volatile water soluble fatty acids
in 5g of fats.
It is a measure of water soluble volatile fatty
acids present in the fat.

111. Iodine number: is defined as number of g of
iodine taken up by 100g of fat.
Iodine is absorbed only at the double bonds of
unsaturated fatty acid residues of fats.
It is directly proportional to the degree of
unsaturation of fatty acids present in the fat.
Example:
Butter ------------- 28
Sunflower oil --- 130

112. Rancidity:
Objectionable taste and odour of fat on standing
exposed to light, moisture and air.
Rancidity results from
1. Formation of aldehydes and peroxides due to
oxidation of unsaturated fatty acids –
Oxidative rancidity.
2. Microbial decomposition of free fatty acids
(produced by the action of lipases) to
ketones – Hydrolytic rancidity.

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