This presentation intends to offer a bird's eye view of bio-molecules in general and lipids in particular along with its beneficial and harmful attributes.

1. LIPIDS: NECESSARY
BUT EVIL

2. Presented by
Dr. N. Sannigrahi,
Associate Professor,
Department of Botany,
Nistarini College, Purulia ( W.B) India

3. LIPIDS
i. You might have come across the different health issues like
increase of LDL, HDL in your family life.
ii. You use different kinds of oils in your daily life for
consumption by cooking and the preparation of fast foods.
iii. Oil paintings and related coatings in household decorations,
iv. Have you heard about biodiesel- sustainable source of fuel,
v. You have heard about fat soluble vitamins,
vi. You use different kind of soaps in your daily life,
vii. Sex hormones are quite known to us,
viii.Many marine animals and the animals of temperate climate
possess high degree of insulation as a part of the production
of chilled environment,
ix. The composition of cell membrane with phospholipids are
known to you as a part of biological knowledge,
x. Major sources of metabolic energy is your endeavor---- all
are answered with the understanding of lipids

5. WHAT IS LIPID ?
Lipids are a heterogeneous group of compounds related to fatty
acids and include fat, oils, waxes and other related substances.
These are oily, greasy organic substances, relatively insoluble in
water and considerably soluble in organic solvents like ether,
chloroform and benzene being hydrophobic in nature. The term
‘Lipid’ was coined by Bloor (1943), a German biochemist.
“ Lipids are naturally occurring compounds which are insoluble in
water and soluble in one or more organic solvents such as
benzene, chloroform, ether and acetone, the so called fat solvents
and on hydrolysis yield fatty acids which are utilized by the living
organisms”. Lipids are thus group of naturally occurring molecules
comprising of C, H, & O that include fats, waxes, sterols, even fat
soluble vitamins, monoglycerides, diglycerides, triglycerides,
phospholipids and others. They play pivotal role in storing energy
with wide functions including the application in nanotechnology
recently.

7. CLASSIFICATION
Lipids are diverse in nature but for wide understanding , they can
be classified as per below. 1.On the basis of chemical composition-
Homolipids or Simple lipids- Esters of fatty acids with various
alcohols like fats, oils (triglycerides, triglycerides) & waxes
Heterolipids or Compound lipids- Esters of fatty acids with
alcohols with additional groups like phosphate, carbohydrate
etc.
2. On the basis of function-----
Storage lipids- Mainly meant for storage as present in
Elaioplasts in plants,
Structural Lipids- structural architecture of the cells like
phospholipids, phosphatidylinositol etc.
3. Based on types of bio-chemical subunits-
Fatty acids, Glycerolipids. Glycerophospholipids,
Sphingolipids, Saccharolipids, Polyketides and the derived
compounds like Sterol lipids, Prtenol lipids etc.

8. SIMPLE LIPIDS
Simple lipids either fats m oils and waxes as stated below:
FATS & OILS
 They are basically triglycerides or triacylglycerides,
98% of dietary lipid and 2% phospholipids or cholesterols or its
esters
Major component of storage fat in plants and animals,
Fats are esters of high molecular fatty acids and glycerol
Non-polar, hydrophobic and no electrically charged
Fats are solid but oils are liquid at room temperature,
Insoluble in water
They may be either animal fats or plant fats, animals fat are
saturated but plant fats are unsaturated with high iodine number,
 Animal fats exhibit oxidative rancidity more frequently than
plant fats,
e.g. Beef fat, pork fat, butter fat, Soybean oil, Olive oil, Corn oil
etc are common in occurrence.

10. WAXES
Derived from the word Weax i.e “ the material of the honeycomb”
having the following properties.
a) Esters of long-chain saturated and unsaturated fatty acids with
long chain monohydroxy alcohols,
b) The fatty acids range in between C14 and C36 and the alcohols
from C16 top C36,
c) Melting point 60℃-100℃ than triglycerides,
d) Waxes are secreted from the cutaneous glands in vertebrates
coating to keep the skin water proof,
e) The plants like Rhodoendron, Calotropis, Nerium, cactus etc
and animals like Whale, Herring, Salmon etc have diverse
biological functions,
f) Biological waxes have a variety of application in
Pharmaceutical, automobile and cosmetic industries.
g) Wax is recently used for many more household purposes

11. COMPOUND LIPIDS
Compound lipids contain fatty acids with alcohols and possess
additional groups like phosphates , carbohydrates etc as per the
nature. It may be of three types ( Folch & Sperry, 1955)-
Phosphoglycerides
Phosphoinositides,
Phosphosphingosides. But they can be broadly summarized under
two categories-
1. PHOSPHOLIPIDS- Most abundant in membranes, never stored
in large quantities, contain phosphoric acid groups; usually contain
one hydrophilic polar ‘head’ group and two hydrophobic non-polar
‘tail’ groups and for this reason, they are known as ‘Polar lipids’. All
the biological membranes possess two layers of phospholipids
molecules , spread over as sheet. The polar heads orients towards
outer cytoplasmic side and the non-polar tails orient towards the
inner side forming hydrophobic core of the membrane. E.g
Lecithin, plasmalogens,

13. GLYCOLIPIDS
a) They are called Cerebrosides or Glycosphingosides
b) Lipids contain mainly monosaccharide
c) Present on the outer surface of the cell membrane,
d) Important constituent of brain (8%)
e) Galactose is the head group in the plasma membrane of
neutral tissues while glucose is the head group of the non-
neutral tissue
f) Glycosphingolipids acts as cell surface recognition molecules
as antigens especially in the blood group substances

15. DERIIVED LIPIDS
It includes the hydrolysis products of simple and compound lipids
and also other various compounds like steroids, terpenes, fatty
acids, alcohol, fatty aldehydes, ketones etc.
STEROIDS-
1. one of the most biological compounds, contains no fatty acids,
non- sapponifiable, separated from fat after the later is
saponified.
2. All steroids may be considered as derivatives of called
cyclopentanoperhydrophenanthrene or sterane,
3. This system consists of three cyclohexane ring-A, B, C fused
to a terminal cyclopentane ring D, making 19 carbon structure
4. Some examples are Cholesterol, coprostanol, cholestanol,
ergosterol, lanosterol etc. Cholesterol, the precursor of bile's
and many steroid hormones, first isolated from gallstones, may
be LDL or HDL; LDL bad for health but HDL good in men and
vice versa in women, found in different organisms.

17. 2. TERPENES
Among the nonsaponifiable lipids in plants are many
hydrocarbons known as terpenes or turpentine,
These hydrocarbons and their oxygenated derivatives have lesser
than 40 carbon atoms,
The simplest terpenes are called monoterpenes (C10H24) called
sesquiterpenes, followed by diterpenes (C20H32) and diterpenes
( C30H48) etc. Carotenoids as found in plants including
Xanthophylls, Lycopene as found in tomato, Carotene like α-
carotene,β-carotene, ƛ- carotene are some of the examples in this
regard to explore the most diverse compounds found from the
natural plant sources. Carotenoids are also called lipochromes or
chromolipids and this is very important one to explore the
diversity of the color of the different plant parts and bring the
color of the foliage.

19. FATTY ACIDS
These are straight chain hydrocarbons containing even number of
carbon atoms , commonly 12-24. Depending upon the saturation, it
may be –
SATURATED- Carbon atoms are fully saturated with hydrogen
atoms like Lauric acid, Palmitic acid, archidic acid, stearic acid
etc.
UNSATURATED- Contain one or more double bonds having
unsaturated carbon atoms like Linolenic acid, Linolic acid as
found in linseed oil, oleic acid having one double bond.
Fatty acids may be Hydroxyls or oxygenated fatty acids and cyclic
fatty acids
OXYGENATED FATTY -ACIDS-In these fatty acids, hydroxyl
group is present on the carbon atom instead of hydrogen as found
in ricinolic acid in castor oil , cerebronic acid in animal lipid.
CYCLIC FATTY ACIDS-Both have carbopentyl ring in its 16 and
18 carbon structure as in Chalmoogra oil.

22. FUNCTIONS OF FATTY ACIDS
1. Saturated fatty acids are not good for health as they block the
arteries and veins but unsaturated fatty acids are good as they
can easily pass through blood stream; PUFA are preferable as
they have higher double bonds.
2. It is the sources of metabolic energy as 1 gm of fat provides 9.3
kcal energy in comparison to 4.1 kcal in carbohydrates.
3. Fatty acid can be stored in storage tissues as they are insoluble
in water,
4. Glucose yields only 36 ATP but when fatty acids like Palmitic
acid is oxidized through β-oxidation AND Krebs cycle and
ETS, a net gain of 130 ATP molecules are generated .
5. The essential fatty acids- Linoleic acid, Linolenic acid &
arachidoric acids are required for the normal functioning of cell.
6. Omege-3-fatty acids reduced the chance of Alzheimer’s disease
7. Phospholipids along with sex hormones, vitamins –all are
derived from fatty acids and play important role in cell health.

23. TRIGLYCEROLS (TG) OR TRIACYLGLYSERIDES (TAG)
Triglycerols are simple lipids having three fatty acids ester linked to
a molecule of glycerol as in Tripalmitin. They bear the following
properties-
Generally colorless, odorless and possess bland taste; capable of
absorbing a variety of odors and flavors during storage,
 They are sparingly soluble in water i.e hydrophobic but freely
soluble in organic solvent like chloroform, ether, acetone and
benzene,
The melting point of the triglycerides are very low, C4-C8 are
liquid at room temperature but C10 and above are solid at room
temperature; further greater degree of the double bond, lower the
melting temperature , for example. Oleic acid with one double
bond, Linoleic acid with 2 double bond and Arachidonic acids with
4 double bonds have 13.4℃, -5℃, and -50℃ respectively .

24. Less specific gravity than water as 0.86 in comparison to water
with 1.0; simple fats float in water than liquid fats,
Presence of double bonds offer geometrical isomerism i.e cis &
trans forms. cis form of fatty acid is Oleic acid while trans form is
elaidic acid. Most of the unsaturated fatty acids are present in
unstable cis-isomer rather than as the most stable trans-forms. In cis-
isomer, the two H atoms an two carbon atoms of a double bonds are
present towards on one sides while trans-form , they are present on
opposite sides.
Triglycerides have high insulating power i.e bad conductor of heat
Triglycerides with other lipids are converted into a number of
small liquid droplets with water or with high emulsifying agents like
soaps, gums, proteins etc having great metabolic significance.
Different fat molecules have to be emulsified before they can be
absorbed by the intestinal walls
Liquid triglycerides uniformly spread over the surface of the water
in the form of unimolecular layer and reduces the surface tension of
water.

25. CHEMICAL PROPERTIES
The triglycerides enjoy some unique chemical properties as stated
below:
HYDROLYSIS-The enzyme lipases break down triglycerides into
three molecules fatty acids and one molecule of glycerol in three
steps in the following steps:
Triglycerides +H2O= Fatty acid (R3-COOH)+ diglyceride,
Diglycerides + H2O= Monoglyceride + Fatty acid ( R2-COOH)
Monoglyceride +H2O= Glycerol + Fatty acid (R1-CooH)
Radicals of R1, R2 & R3 may be similar or dissimilar.
SAPONIFICATION-It is the phenomenon of hydrolysis of fats by
alkali which leads to the transformation of glycerol and salts of
fatty acids , known popularly as soaps. Thus , salt of the fatty acid
is commercial soap .Soaps with hard soap having salt of higher
fatty acids or soft soap having potassium salts of higher fatty acids
used as bathing soaps. Calcium soaps are used as lubricating agents
while zinc soaps are used as talcum powder and cosmetics. Lead
and Mg soaps are used in paint and draying

27. HYDROLYTIC & OXIDATIVE RANCIDITY
If fats like butter or ghee are kept for longer period, they become
rancid i.e unpleasant odor and flavor becoming unpalatable due to the
growth of the different microorganisms. The rancidity liberates the
enzymes, lipases and break down fats into glycerol and free fatty
acids. These fatty acids impart rancid flavor . If the butter or ghee kept
in the exposure of the atmospheric oxygen , it causes the autoxidation
to short chain fatty acids and aldehydes give rancid flavor. Oxidative
rancidity is very common in animal fats than vegetable fat as the later
contain lots of antioxidants to reduce the oxidation.
HALOGINATION-The unsaturated fatty acids can be halogenated
with different halogens like iodine & bromine at the double bonds at
room temperature in a solution of methanol or acetic acid.
OXIDATIVE REACTIONS-Different oxidation reactions are used for
establishing the position of double bonds in the unsaturated fatty acid
chain. This helps in the establishment of fat or lipid structure.

29. HYDROGENATION
Unsaturated fatty acids in free or bound state with lipids by
reaction with hydrogen produce saturated fatty acids , catalyzed
by nickel, palladium or platinum. The hydrogen atoms are added
at the carbon-carbon double bonds. This reaction has great
significance for commercial purpose as the inexpensive vegetable
unsaturated oils are converted into solid fats that are used in
different confectioneries and the manufacture of candles. For
example, oleic acid , an unsaturated fatty acid converted into
stearic acid , a product of the hydrogenation of saturated fatty acid
as end product.
OZONOLYSIS- When ozone transforms the unsaturated fatty
acids by oxidation split up the double bonds and initially produce
ozonide and later breaks down into 2 molecules of aldehydes
groups is called Ozonolysis. There are other chemical properties
found in this group.

31. FUNCTIONS OF TRIGLYCERIDES
The triglycerides plays a very significant role for human health.
Some of the important functions as extended by the said molecule as
stated below:1. The unsaturated vegetable oils are good for human
health like flax seed oil, soybean oil, linseed oil, olive oil. It is the
main component of human skin oil.
The fatty acids undergoes β-oxidation release huge energy in the
form of energy rich bond, ATP for performing the different biological
attributes of the living organisms in general and human in particular.
Triglycerides are the key component of VLDL and play an
important role in metabolism
The high levels of triglycerides in the blood stream linked to
atherosclerosis and may cause the risk of the heart diseases and
stroke. The higher the level of this compound may cause the higher
the risk factor to suffer from the same issue.
Oil paintings and related coatings are done using linseed oil

32.  Triglycerides are also important for the production of
biodiesel as a part of the solution of fossil fuels for
sustainable development.
 Glycerol, a component of triglyceride is used in the
manufacture of food and in the production of pharmaceutical
products.
 Triglycerides are used in staining industry.
 Triglyceride , as a blood lipid, helps in bidirectional
transference of adipose fat and blood glucose from the liver,
In addition to the aforesaid functions, triglycerides also extend a
lot of biological functions for the plant and animals life including
human beings. It is one of the important biomolecules that needs
for the sustainable life but very often it becomes detrimental for
human health. In this context, it may also refereed as necessary
but evil in certain circumstances.

33. References:
1. Google for images,
2. Different open sources of information of WebPages
3. Biochemistry- Lehninger
2. Biomolecules & Cell Biology- Arun chandra Sahu,
3. A textbook of Botany (Vol II) Ghosh, Bhattacharya,
Hait
4. Fundamentals of Biochemistry- Jain, Jain, & Jain,
5.A Textbook of Genetics- Ajoy Paul
DISCLAIMER:
This presentation has been made to enrich open source of
knowledge without any financial interest. The presenter
acknowledges Google for images and other open sources
of information to develop this PPT.