The document provides information about lipids including their definition, functions, classification, properties and metabolism. It defines lipids as compounds that are insoluble in water but soluble in organic solvents and on hydrolysis yield fatty acids. Lipids include simple lipids like fats and oils, compound lipids like phospholipids and glycolipids, and derived lipids like fatty acids. They serve important functions like energy storage, structure of cell membranes, and as signaling molecules. The document also discusses lipid hydrolysis, saponification, hydrogenation and rancidity.

1. WELCOME

2. Submitted to:-
Dr. H. S. Bhadauria
Asso Professor, Dept. of GPB
SDAU, S.K. Nagar
Submitted by:-
Vaghela Gauravrajsinh K
M.Sc. (Agri.)
Reg.no:-04-AGRMA-01840-2018
SDAU, S.K. Nagar
LIPIDS

3. LIPIDS
 Fats and their derivatives are known collectively as lipids. (Greek word: lipos= fat)
 The word lipids is derived from the Greek word “ lipos ” meaning fat.
 The principal component of lipid is fatty acid. The term lipid was first time given by
biochemist BLOOR in 1943.
 Bloor defined lipid as “Naturally occurring compound which are insoluble in water and
soluble in organic solvents such as benzene, chloroform, ether etc. On hydrolysis they
yield fatty acids.”
 Lipids are defined as chemically heterogeneous group of compounds of biological
importance that are relatively insoluble in water but freely soluble in non-polar
solvents such as chloroform, benzene, ether, hot alcohol, acetone, etc.

4. FUNCTIONS OF LIPIDS
1) Storage form of energy (triglycerides).
2) It is a concentrated source of energy as it provides more than twice energy (9 kcal/ g) as compared to
carbohydrates(4 kcal/ g).
3) Structural components of bio membranes (phospholipids and cholesterol).
4) Provide essential fatty acids (EFA) viz, linoleic, linolenic and arachidonic acids
5) Metabolic regulators (steroid hormones and prostaglandins).
6) Act as surfactants, detergents and emulsifying agents (amphipathic lipids).
7) Act electric insulators in neurons.
8) Provide insulation against changes in external temperature (subcutaneous fat).
9) Give shape and contour to the body.
10) Protect internal organs by providing a cushioning effect (pads of fat).
11) Help in absorption of fat soluble vitamins (A, D, E and K).
12) Improve taste and palatability of food. Contribute aroma through nose and texture of food which is
responsible for the mouth feel.

5. Classification of Lipids
1. Simple lipids
2. Compound lipids
3. Derived lipids
4. Lipid complexed to other compounds

6. Classification of Lipids
Lipids
Simple Lipid Compound Lipids Sterols Hydrocarbon
Vitamin Fat, Oil Wax Cholesterols A, D, E & K
Phopho Lipids Glyco Lipids Ganglioside Lipo Protein
Lecithin Cerebrosides N-acetyl Neuramic Acid + Protein + Triglyceride +
Cephalic Fatty acid + Hexoses Cholesterols or Phosho Lipids

7. Simple Lipids Compound Lipids Derived Lipids
Esters of fatty acids with glycerol
and monohydric alcohols.
Esters containing chemical groups in
addition to alcohol and fatty acids.
Substances derived from simple
and compound lipids by
hydrolysis. Alcohols, fatty acids,
aldehydes, ketones, sterols and
hydrocarbons
Depending upon the constituent
alcohols they are further subdivided
into fats or oils and waxes.
Depending upon the chemical groups they
are further subdivided into phospholipids,
glycolipids, sulpholipids and lipoproteins.
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Waxes are esters of fatty acids and
alcohols other than glycerol
Glycolipids contain hexose units preferably
galactose along with fatty acids and alcohol
e.g. Cerebrosides.
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e.g.,Plant wax-carnauba wax; Insect
wax-beeswax.
Plant sulpholipids contain sulphated hexose
with fatty acids and alcohol
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Animal wax – lanolin Lipoproteins contain protein subunits along
with lipids. Depending upon density and
lipid compound they are further classified
as VLDL, LDL and HDL.
-----

8. SIMPLE LIPID
 Simple lipids are the esters of fatty acids with various long chain alcohols.
 Fatty acids are of two types.
1)Saturated Fatty acids.
2)Unsaturated fatty acids.
SATURATED FATTY ACIDS
A. Butyric acid CH3CH2CH2COOH Butter
B. Caproic acid CH3 (CH2) 4COOH Butter
C. Caprylic acid CH3 (CH2)6 COOH Coconut, palm oil
D. Lauric acid CH3 (CH2)10 COOH Laurel, kernel oil
E. Myristic acid CH3 (CH2)12 COOH Nutmeg oil
F. Palmitic acid CH3 (CH2)14 COOH Palm oil
G. Stearic acid CH3 (CH2)16 COOH Cocoa butter
H. Arachidic acid CH3 (CH2)18 COOH Peanut oil.

9. UNSATURATED FATTY ACIDS
A. Oleic acid (C18 ) One double bond Olive oil
B. Linoleic acid (C18 ) Two double bond Linseed oil, Soybean oil
C. Linolenic acid (C18 ) Three double bond Linseed oil
D. Erucic acid (C22 ) One double bond Mustard oil
E. Arachidonic acid (C20 ) One double bond Ground nut oil
No. (B), (C) and (E) are the essential unsaturated fatty acids required by
the human being.

10. COMPARISON OF FATS AND OILS
FAT
1. Esters of fatty acids + glycerol
2. Solid at room temperature
3. Low molecular weight
4. More saturated fatty acids
5. High saponification value
6. Low iodine value
OILS
1. Esters of fatty acids + glycerol
2. Liquid at room temperature
3. High molecular weight
4. Higher unsaturated fatty acids
5. Low saponification value
6. High iodine value

11. CHEMICAL PROPERTIES OF SIMPLE LIPIDS
 HYDROLYSIS :- They are hydrolyzed by super heated steam, strong alkali, dilute mineral
acid or lipase enzyme.
Lipids + H 2O Fatty acid + glycerol
Lipase enzyme
 SAPONIFICATION :- When fat or oil reacts with NaOH or KOH, they yield salts of fatty
acid (soap) and glycerol.
Neutral fat + NaOH / KOH Soap + glycerol
 HYDROGENATION :- Unsaturated fatty acids react with hydrogen in presence of nickel at
150-190 0 C to give saturated fatty acids. Liquid oil is converted to solid fat. Hydrogenation is
the process used for preparing the artificial ghee (vegetable oil).
Unsaturated fatty acid + H2 Saturated fatty acid
CH3 (CH2)7 CH = CH CH2COOH CH3 (CH2)7 CH2 CH2CH2COOH

12.  HYDROGENATION: Unsaturated fatty acids react with hydrogen in presence of nickel at 150-190 0
C to give saturated fatty acids. Liquid oil is converted to solid fat. Hydrogenation is the process used
for preparing the artificial ghee (vegetable oil).
Unsaturated fatty acid + H2 Saturated fatty acid
CH3 (CH2)7 CH = CH CH2COOH CH3 (CH2)7 CH2 CH2CH2COOH
 HALOGENATION: When unsaturated fat is treated with halogens (I2 / Br2 /Cl2), the fat is converted
to halogenated compounds.
E.g. Iodine value is a useful tool to know the amount of unsaturation in the fat.
CH3 (CH2)7 CH= CH CH2COOH + I2 / Br2 /Cl2 CH3 (CH2)7 CH - CH CH2COOH
I/Br/Cl I/Br/Cl
Halogenated compound

13.  RANCIDITY :- When butter/oil/fat is stored for a long time, they often become rancid due to
hydrolysis/oxidation. The rancid fat gives off flavour, bad smell and unpleasant taste. The
rancidity can be defined as the production of bad unpleasant smell in oil or fat is called
rancidity.
 The rancidity is of two types.
1. Hydrolytic rancidity
2. Oxidative rancidity
a) Aldehydic rancidity
b) Ketonic rancidity
1. Hydrolytic rancidity :- This is developed by the action of microbial lipase enzyme which split
the triglycerides and produce low molecular weight (C4 – C10 ) fatty acid such as butyric acid. This
butyric acid produces bad smell in the butter.
Butter or butterfat + Lipase + 3H20 Glycerol + Butyric acid
2. Oxidative rancidity :- This type of rancidity develops due to oxidation of unsaturated fats to
produce either the cleavage or polymerisation of fatty acid.
Two types of oxidative rancidity a) Aldehydic rancidity b) Ketonic rancidity

14. 1) Aldehydic rancidity: There is production of peroxides when these peroxides are converted into
aldehyde which gives bad smell in fat.
O – O
HC = CH + O2 - C - C C = O
H H H
Unsaturated fatty acid Peroxide Aldehyde
2) Ketonic rancidity: When ketones are formed from the β oxidation of saturated fatty acid, then
keto acids are formed. Elimination of CO2 leads to rancid ketone formation to produce bad smell.
CH3 (CH2) n COOH CH3 CH2- CH2 – C – COOH
Saturated fatty acid Keto acid O
CH3CH2CH2COCH3
Ketone (bad smell)

15. COMPOUND LIPIDS
 They are the complex esters of aliphatic mono carboxylic fatty acid with aliphatic alcohols having
nitrogenous base such as choline, ethanolamine etc.
1) PHOSPHOLIPIDS:- These are the esters produced by the combination of fatty acid, glycerol,
phosphoric acid and a nitrogenous base.
 E.g. Lecithin, Cephalic, Plasmlogens, Phosphoinositis, Sphingomyelins
 LECITHIN:-
 They are found in the growing tissues, egg yolk, brain, kidney, soybean, nervous tissues, blood etc.
 They are occurring in two isomeric forms.
 a) α - Lecithin and b) β – Lecithin
 CEPHALIN:-
 The difference between lecithin and cephalin is only in the structure. Choline residue is replaced
with the cholamine, attached to glycerol. Their main function is in nervous tissues.
 Plasmalogen, phosphoinositides and Sphingomyelins are components in the human tissues and
have little importance in the plants.

16. 2) GLYCOLIPID:- It contains carbohydrate moiety particularly galactose in the structure.
 E.g. Cerebroside is present in brain tissues and act as neuro transmitters.
 STEROLS
 Sterols are the solid alcohols with high molecular weight having many cyclic rings in the
structure. ( Steros = solid ) , ( ol = alcohol ). They are widely distributed in plant, animals and
micro organisms in conjugated form.
 CHOLESTEROL :- It is a animal sterol with a molecular formula of C27H45 OH
 ERGOSTEROL:- It is a mycosterol with a molecular formula C28H43 OH.
 Sistosterols or Stigmsterols : It is a phytosterol of plant origin.

17. METABOLISM OF LIPIDS
1. ANABOLISM:-
Glucose Glucose
Glycolysis Glycolysis
Glyceraldehyde Pyruvic acid
Glycerol Acetyl Co –A
Fatty acid synthesis
Glycerol + Fatty acid Lipid

18. 2. CATABOLISM:-
Lipid Fatty acid + Glycerol
Lipase
β –oxidation Glycolysis
Acetyl co-A Pyruvic acid Acetyl co -A
TCA cycle TCA cycle
CO2 + H2O + ENERGY