Lipids are a heterogeneous group of compounds that are chemically esters of fatty acids. They function as fuels for the body, provide insulation and padding for organs, and are involved in cell membrane structures. The main types of lipids include fatty acids, triglycerides, phospholipids, and steroids like cholesterol. Lipids play important roles in energy storage, as structural components of cell membranes, and in transporting fat-soluble vitamins. They undergo reactions like hydrolysis, hydrogenation, and oxidation. Diseases related to lipid metabolism include obesity, hyperlipidemia, and lipidosis.

1. LIPIDS
Shalini N. Barad,
Assistant Professor,
Appasaheb Birnale College of Pharmacy.

2. • What are lipids ?
Lipids are heterogeneous group of compounds, which
are chemically esters of fatty acids.
These are insoluble in water but soluble in organic
solvent such as ether, benzene etc.
❑ Functions:
1. Acts at a fuel
2. It provides excellent insulation
3. Also provide padding to protect the internal organs
4.Derived lipids are important building blocks of
biological active materials
5. Lipids are involved in the cell wall constitutions e.
g. phospholipids ,and acts as barrier in between the
extra and intra cellular fluids.
6. they help in transport of fat soluble vitamins
7. Serve as cellular metabolic regulators.

3. Fatty acid – It consist of long chain of hydrocarbon
having carboxyl group at one end & methyl group
at another end.
They are of 2 type – i) Saturated fatty acid
Ii) Unsaturated fatty acid
i) Saturated fatty acid—It does not have any double
bond

4. Ii) Unsaturated fatty acid– Fatty acid which have one
or more double bond in their molecule are called
unsaturated fatty acid.

6. Eicosanoids—It contain 20 carbon polyenoic
fatty acids.
It consist of prostanoids (prostaglandins,
prostacyclin & thromboxanes), leukotrienes, &
lipoxin.

7. 0 What are triglycerides ? give its functions.
• Triglycerides are also called as triacylglycerols or fats
and oils. These are esters of glycerol with fatty acids.
• The fats and oils that are widely distributed in both
plants and animals are chemically triacylglycerols.
• They are soluble in water and non-polar in character
and commonly known as neutral fats. They contribute
• about 98% of total dietary lipids, remaining of 2%
consists of phospholipids and cholesterol and esters.
• They are tasteless, colorless, odourless , and neutral in
reaction.
• Functions-
1. acts as food reservoir in the human body
2. acts as insulator for the loss of body heat.
3. acts as padding material for protecting internal organs
4. acts as fuel.

9. ❑ Classification:
1.Simple lipids:
Esters of fatty acids with alcohol.
• Fats & oils : Castor oil
• Waxes : Beeswax
2.Compound Lipid
•a)Phospholipids
i)Glycerophospholipids– Lecithin, cephalin, Plasmalogen
ii)Sphingophospholipids- Sphingomyelins
• b) Glycolipids: i) brosides
ii) Gangliosides
• c) Lipoproteins: Contain proteins

10. • d) Other complex lipids– i) Sulfolipids
ii) Aminolipids
iii) Liposaccharides
3.Derived Lipids:
• Eg: Alcohols, Glycerol, Fatty acids etc
4.Miscellaneous Lipids:
• Eg : Carotenoids, Squalene.
5.Neutral Lipids:
• They are mono, di, triacylglycerols, cholesterol, cholesteryl
esters.

11. 1. Simple lipids:
A) Oils & Fats -Esters of fatty acids with glycerol
as alcohol.
B) Waxes- They are esters of fatty acid with
higher monohydric alcohol.
Eg: 1. Spermaceti, beeswax, Cholesterol ester,
Vit. A, Vit. D ester.

12. Fats Oils
1. Fats are solids at room temp These are liquid at room temp
2. Contain greater amounts of
Saturated fatty acids
Contain greater amounts
ofunsaturated fatty acids
3. Act as food reservoir Mostly protective in functions
e. g. bees wax. e. g. castor oil
•Differentiate between fats and oil.

13. 2. Compound Lipid: These are esters of fatty
acids containing groups such as phosphate,
nitrogenous base, carbohydrates, proteins etc
in addition to an alcohol and a fatty acids.
• Types:
1. Phospholipids ( lecithin, cephalin)
2. Glycolipids.
3. Lipoproteins etc.

14. A)Phospholipid: Phospholipids are compound or
complex lipids that are esters of fatty acid with
alcohol & contain additional group phosphoric acid
i)Glycerophospholipids: contain glycerol as
alcohol.
All phosphoglycerides are derived from δn-Glycero
-3-phosphoric acid
Phosphoric acid is esterified with hydroxyl group of
C3,C1,C2 hydroxyl group get esterified with fatty
acids.
Eg. Lecithin, Cephalin.

16. ii)Sphingophospholipids:
Sphingophospholipids are obtained from
sphingosine,an amino alcohol.
Hydroxyl group of sphingosine is esterified
with phosphocholine and sugar.
e.g. Sphingomyelines

17. Functions:
1. Phospholipids form structural components of
membrane & regulate membrane
permeability.
2.Phospholipids are responsible for maintaining
conformation of electron transport chain
components & so cellular respiration
3.Phospholipids participate in absorption of fat
from intestine & also transport of lipids
4.Phospholipids act as surfactants
5. They are involved in signal transmission
across membranes.
6. Cephalins participate in blood clotting.

18. B) Glycolipids:
combination of carbohydrates & lipids.
Eg– Cerebrosides (consist of cerebronic acid +
Sphingosine + Sugar sulphate/ Sugar) mostly seen
in brain, gangliosides (sialic acid).
C)Lipoprotein– Lipids (triacylglycerols/
Phospholipid/ cholesterol) & protein & found in
mitochondria cell membrane, ER, Nuclei.
D)Lipopolysaccharides– found in gram negative
micro-organism. When these are released in blood
they are toxic. Also called as endotoxin.

19. 3. Derived lipids:
It consist of acid, steroids, fat soluble vitamins,
eicosanoids.
i) Steroids– It consist of steroidal nucleus called as
cyclopentanoperhydrophenanthrene.
Eg: Cholesterol
• It is found in animal tissue especially in brain & spinal
cord.
• It is major component of plasma membrane.
• Properties —
1. Crystalline solid, insoluble in water, soluble in organic
solvents.
2. It is precursor for bile acids, sex hormones,
corticosteroids & vit D

21. ❑ Chemical test for steroids:
These tests confirm presence of
cholesterol
1. Liebermann-Burchard test:
When 2 ml of chloroform + solution of
cholesterol + 10 drops of acetic anhydride
+ 2 drops of conc. sulphuric acid,
deep red colour changes to green colour

22. 2. Salkowaski test:
• When 2 ml of chloroform + solution of
cholesterol + 2ml of concentrated sulphuric acid,
after waiting for 3min layers separate.
Chloroform layer turns red &
acid layer shows greenish fluorescence
3) Formaldehyde-H2SO4 Test:
• To a solution of cholesterol in chloroform in
dry test tube, if 2 ml of formaldehyde-
sulphuric acid solution is added, cherry
colour develops.

23. • Rancidification of Fats and Oils:
1. When fats and oils are exposed to light, air, heat, moisture
for a longer time, develops disagreeable and objectionable
odour. Such oil or fat is said to be rancid, and the
phenomenon is called as rancidification.
2. The bad and objectionable odour is because of liberation of
volatile fatty acids like butyric acid, caproic acid, caprylic
acid.
3. The rancid oils or fats shows acidic reaction due to
decomposition of glyceride resulting into more amount of
free acid.
4. Rancid oil shows high acid values.
5. Rancidification can be prevented by antioxidants Vitamin
E, BHT.

24. METHODS USE TO STUDY FATS OR OIL
i)Acid value
It is the number of milligram of KOH required to
neutralize the free fatty acids present in 1 gram of
fat or oil.
ii)Saponification value
It is the number of milligram of KOH required to
saponify i.e. hydrolyse the free and combined
fatty acids in one gram of given fat or oil.
iii) Iodine value:
It is the number of grams of iodine required to
saturate or absorbed by 100gms of fat.
iv) Reichart- miesel number:
It is the number of milliliters of 0.1N KOH
required to neutralize the volatile fatty acids
contained in 5gm of fat or oil.

25. v) Polensky value:
It is the number of milliliter of 0.1 N KOH required
to neutralize the insoluble fatty acids from 5gm of
fat or oil.
It is an indicator of how much volatile and insoluble
fatty acids present in total fats and oil.
vi) Acetyl number:
It is the number of milligram of KOH required for
the neutralization of acetic acid obtained by
saponifying 1gm of an acetylated fat or oil.

26. • Explain the role of lipids in biological
membrane:
1. The major component of biological membrane is
phospholipid.
2. Phospholipid has 2 long chains of hydrocarbon of
fatty acids.
3. The chains are hydrophobic and have strong polar
group.
4. When phospholipids are added to aqueous medium
they form micelles, monolayer & bilayer, depending
on the concentration of phospholipids.
5. The hydrophilic & hydrophobic interaction of
phospholipids is forming bilayer in water.

28. 6. Hydrophobic tails are hidden from aqueous
environment and form an internal hydrophobic
phase whereas hydrophilic heads are exposed to
the surface.
7. Bilayer system of this type is extensively studied
as model of natural membrane.
8. Biomembranes are made up phospholipids
lipoproteins, glycoproteins and proteins all these
components are assembled together by non
covalent interactions

30. Q. Explain with chemical reaction, saponification
reaction of simple fats.
1. When triglycerides in fat/oil react with aqueous
NaOH or KOH, they are converted into soap and
glycerol.
2. This is called alkaline hydrolysis of esters. Since this
reaction leads to the formation of soap, it is called
the Saponification process.

32. • Role of lipids:
• Energy storage :Triacylglycerols, stored in adipose
tissue, are a major form of energy storage
• Acting as structural components of cell membranes:
The glycerophospholipids are the main structural
component of biological membranes,
• Dietary fats help to dissolve fat soluble vitamins: (A,
D, E and K)
• Lipids play diverse and important roles in nutrition
and health. Many lipids are absolutely essential for
life.
• Humans have a requirement for certain essential
fatty acids, such as linoleic acid, linolenic acid. These
are provided by lipids.
• Lipids provide excellent insulation as fat is bad
conductor of heat.
• Fats provide padding to protect internal organs
• Lipoproteins and glycolipids are essential for cellular
integrity.

33. • Chemical Properties:
• Undergo hydrolysis in presence of acid,
alkalies
• Undergo hydrogenation, halogenation in
presence of platinum, nickel
• Undergo oxidation & forms aldehydes, ketones,
resins
• Rancidify on standing for long period

34. • Diseases related to lipid metabolism
1. Obesity is due to accumulation of excess of body fat
2. Lipidosis abnormal lipoproteins in blood or specific
lipids in blood tissue
3. Hyperlipidemia: Increase in plasma cholesterol or
plasma triglycerides
4. Hyperlipoproteinemia: increase in lipoproteins.
5. Ketosis: Formation of ketone bodies
6. Lipid storage diseases (Enlargement of liver and
spleen, leads to mental retardation)
• Niemann pick disease
• Gaucher’s disease
• Metachromatic leukodystrophy

35. IMP QUESTIONS:
1. Define lipids, & classify it with example?
2. Define compound lipids, & classify it in details.
3. Draw structure of cholesterol, & explain chemical test
for it in detail.
4. Explain biological role of lipids in biological membrane.
5. Explain Rancidification in details.
6. Define the following terms:-
i)Acid value, ii)Sap value, iii)Acetyl value, iv)
Reichert-Meissel number, v)Polensky value.
7.What are triglycerides & give its function?
8. Draw the structure of : Cholesterol, lecithin, cephalin,
isoprenoid unit, Androsterone, progesterone.