Lipids are
chemically defined as a substance that changed in soluble in water and soluble
in organic compound like chloroform, ether, benzene, etc.

   Lipids are the
main constituents of plant and Animal cells.

   Leopard is a type
of organic molecules found in a living thing. It is oily or waxy.

Biological function
of Lipids.

   Building block for
membrane phospholipid are present in almost all membranes.

   Installment of
organs of cell.

   Carries for fat
Soluble Vitamins.

   As energy source
lipids provide 9kcl of energy per gram.

   Provide shop
absorption & insulation.

   Dietary fibre act
as carrier of Lipids Soluble Vitamins into cells of small intestine.

Biological importance
of Lipids:-

dietary compounds and storage form of energy.

components of biomembrane.

insulation against changes in external temperature.

      Giving shape
and outline to the body.

internal organs by providing a cushioning effect.

      Provide shock
absorption and insulation.

Classification of

1. Simple Lipids

a) Fats

b) Waxes

2. Compound Lipids

3. Derived Lipids

Fatty acid:-

      It consists of
long chain of hydro-carbon having carboxyl group at one end and methyl group at
another end.

      Fatty acids
very in chain length and degree of unsaturation.

It is classified into
two classes.

1. a) Saturated fatty acids

2. b) Unsaturated fatty acids

a)      Saturated fatty acids:-

      These acids
does not contain any double band called saturated fatty acids.

      e.g. : Palmitic
acid, Stearic Acid

b)    Unsaturated fatty acids:-

      Fatty acid
which have one or more double bond in their molecules are called unsaturated
fatty acid.

      g. :-
polmitoliec acid, Arachidonic acid.

Essential Fatty

      The fatty acids
which cannot be synthesized in the body are etermed as essential fatty acids.

      These are
essential for complete nutrition of animals and therefore should be supplied
through diet.

      These are
polyunsaturated fatty acids are linoleic acid.

A.     Simple Lipids

      Simple Lipids
are a fatty acid ester of different alcohols and carries no other substances.

a)      Oil and Fats:-

      These Lipids
are esters of fatty acid and alcohol with glycerol (Glycerin).

      At room
temperature fats are solid because largely they are made up of unsaturation
fatty acids.

      While oil
contain one or more unsaturated fatty acids due to which oils are liquid at
room temperature.

b)    Waxes:-

      Waxes are
esters of fatty acids with higher monohydric alcohol.

      g. Bee’s waxes,
Vitamin A ester, Vitamin D ester, cholesterol ester.

B.     Compound Lipids

      Ester of fatty
acids + Alcohol + Other group like phosphate, Nitrogenous base, Carbohydrate
Protein etc.

1) Phospholipids:-

      The term phospholipid
is used to describe any lipid can containing phosphorus.

contain phosphoric acid, fatty acids, alcohol and generally a Nitrogenous base.



2) Glycolipids:-

      Combination of
Carbohydrates and Lipids are Glycolipids.

      Basically they are amphipathic carbohydrate
glyceride derivative but do not contain phosphate. E.g:- Cerebroids,

3) Lipo-proteins:-

containing Lipids are Proteins found in mitochondria endoplasmic reticle and


      These are found
in gram negative micro-organism which are giant macro-polymer very complex in
structure when these are released to blood stream produce untoward reaction and
are toxic.

      They are also
known as endotoxins.

      Pyrogens are

C.  Derived Lipids

      This class of
Lipids consists of fatty acids, steroids, fat soluble vitamin like – Vitamin A,
Vitamin D, eicosanoids like prostaglandin ketone bodies glycerol and other

      Steroids:- Steroids are Lipids because they
are hydrophobic and insoluble in water.

      Cholesterol is
the most common steroid and is the precursor of Vitamin D, Testosterone,
Estrogen progesterone etc.

      The example of
steroids found in biologicals system are cholesterol, Bio-acids, Vitamin-D, Sex
Hormone etc.

Cholesterol is an important steroid found in animal tissue especially in brain
and spinal cord. It is major component of plasma membrane and plasma

Qualitative tests for

1)    Solubility:-

      Solubility of
Lipid in organic solvents depends on length of hydro-carbon chain of the fatty
acids attached to glyceride.

      Lipids are
soluble in solvents like- Chloroform, ether, alcohol, hexane etc.

2)    Formation of translucent spot on paper:-

writing paper becomes semi-transparent when a drop of oil is applied to paper.

3) Emulsification:-

      When oil or
liquid fat is shaken with water. It is finely divided and is displayed in the water
to form what is known as emulsion.

      Shake a drop of
oil with little water in a test tube. The oil becomes finally divided forming
an emulsion.

4)    Iodine
absorption test:-

      This test is
for unsaturated fatty acids for fat. A drop of iodine is added to fat (Fat some
is prepared in chloroform) and shaken.

      This solution
will decolorizes if unsaturated fatty acid is present.

Disease related to
fat metabolism:-

Excessive excretion of fat in the faces is known as
steatorrhea but it is either maldigesting of fats due to inadequate secretion
of pancreatic lipase or bile salts or even may be defective absorption due to
intestinal disease like – coeliac disease.


1. Obesity is another disorder which is due to accumulation
of excess of body fat.


1. This denotes the abnormal Lipo-proteins in blood or
specific Lipids in tissues


1. Enlarge liver spleen

2. Abdomen swell

3. Tiredness pain

4. Bone broke


1. It is a condition in which plasma cholesterol or plasma
triglyceride level is increased. This condition occurs due to inherent genetic


1. Chest pain

2. Heart attack

3. Sores on the toes.


      An oilment in
which cholesterol or triglycerides containing Lipo-proteins are reported in
high concentration in the blood.


1.  Enlarge liver

2.  Heart disease.

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