Lipids are a diverse group of organic compounds that are hydrophobic and insoluble in water. They include fats, oils, waxes, sterols like cholesterol, and phospholipids. Lipids serve important functions like energy storage, creating cell membranes, and cell signaling. The presentation defined lipids and their main classes like simple lipids, compound lipids, and derived lipids. It described the types and functions of important lipids like fatty acids, phospholipids, glycolipids, cholesterol, and triglycerides. Lipids play essential roles in the body as an energy source, building cell membranes, and carrying vitamins.

1. - -
Zoology Presentation

2.  We would like to express our special thanks of gratitude to our zoology teacher “Mr.
Mohit Kumar ” for providing us relevant material guidance and support in completing our
Presentation.
Acknowledgement
 We would like extend by thanks to our friends and family who helped us with their
valuable guidance and suggestions for completion of our presentation.

3. INTRODUCTION
What are Lipids ?
1
 The words lipid is derived from the Greek word “ lipos ” which means fat.
 A group of organic compounds which are chemically diverse at the same time
insoluble in water are called Biological lipids.
 They are usually soluble in non-polar solvents such as ether, chloroform or
benzene.
 Lipids are hydrophobic in nature due to the predominance of hydrocarbon
chains.(-CH2-CH2-CH2-CH2) in their structures.
 Unlike the proteins, nucleic acids, and polysacchraides, lipids are not polymer.
 They are the chief storage form of energy, they provide 6-fold as much energy as
an equivalent mass of glycogen.

4.  Fat and oils are the principle stored forms of energy in many organism.
 Lipids participate in oxidative phosphorylation.
Definition
 Lipids may be regarded as organic substances relatively insoluble in water, soluble in
organic solvents, potentially related to fatty acids and utilized the living cells.
 These organic compounds are non polar molecules, which are soluble only in non
polar solvents and insoluble in water because water is a polar molecule. In the human
body, these molecules can be synthesized in the liver and are found in oil, butter,
whole milk, cheese, fried foods, and also in some red meats.

5. Properties of lipids
 Lipids are a family of organic compounds, composed of fats and oils. These
molecules yield high energy and are responsible for different functions within the
human body. Listed below are some important characteristics of Lipids.
 Lipids are oily or greasy non polar molecules, stored in the adipose tissue of the
body.

6. Functions of lipids
 They serve as a storage form of metabolic fuel.
 Examples like fatty acid and Tricyglycerol.
 They serve as a transport form of metabolic fuel.
 Examples like free fatty acid, triglyceride and cholesterol ether.
 They provide the structural components of membrane like phospholipids,
glycolipids, galctolipids, sphingolipids,
 Lipids are a heterogeneous group of compounds, mainly composed of hydrocarbon
chains.
 Lipids are energy-rich organic molecules, which provide energy for different life
processes.
 Lipids are a class of compounds characterized by their solubility in nonpolar
solvents and insolubility in water.
 Lipids are significant in biological systems as they form for a mechanical barrier
dividing a cell from the external environment known as the cell membrane.

7. Classification of Lipids
 Lipids can be classified into two main classes :
A. Nonsaponifiable lipids.
B. Saponifiable lipids.
Nonsaponifiable Lipids
A nonsaponifiable lipid cannot be disintegrated into smaller molecules through hydrolysis.
Nonsaponifiable lipids include cholesterol, prostaglandins etc.
Saponifiable Lipids
A saponifiable lipid comprises one or more ester groups, enabling it to undergo hydrolysis
in the presence of a base, acid, or enzymes, including waxes, triglycerides, sphingolipids,
and phospholipids.

8. Ve
Classification based on Chemical Composition
Based on their chemical composition lipids can be classified into three classes.
 Simple lipids or Homolipids : These are esters of fatty acids with various
alcohols.
Eg : Triglycerides,Glycerol
 Compound lipids or heterolipids : These are esters of fatty acids with alcohol
and possess additional groups also.
Eg : Phospholipds,Glycolipids
 Derived lipids : These are the substances derived from simple and compound
lipids by hydrolysis.
Eg : Sphingosine,Steroid derivatives.

9.  The simple lipids include fats, oils and waxes. These simple lipids are
derivatives of lipid are derivatives of lipid-like substances call fatty acids.
Fats: Esters of fatty acids with glycerol. Oils are fats in the liquid state
Waxes: Esters of fatty acids with higher molecular weight monohydric alcohols
As mentioned above the main simple lipids are triglycerides steryl esters, and
wax esters.
Types of Lipids
Simple Lipids
2
Fatty acids are the building blocks of the fat in our bodies and in the food we eat.
During digestion, the body breaks down fats into fatty acids, which can then be
absorbed into the blood.They are long-chain carboxylic acids(generally greater than
about 12 carbons) that have no solubility in water.

10. Hydrolysis of these lipids yields glycerol and fatty acids, sterols and fatty acids, and fatty
alcohols plus fatty acids, respectively. The most important of these simple lipids for food
scientists are the triglycerides. They are the major components of edible oils and fats,
often representing more than 95% of refined oils.

11. Compound Lipids
They are fatty acids esterified with alcohol; but in addition they contain other
groups.
Depending up on these extra groups,they are sub-classified as :
 Phospholipids containing phosphoric acid.
Glycolipids (glycosphingolipids): Lipids containing a fatty acid, sphingosine,
and carbohydrate.
Other complex lipids: Lipids such as sulfolipids and amino lipids. Lipoproteins
may also be placed in this category
Phospholipids
 A phospholipid is an amphipathic molecule constructed from four components : fatty
acid, phosphate, alochol and glycerol or sphingosine.
 Also called as phosphatides, contains a phosphorous atom.

12.  The phospholipids are very important structural components of all cell membranes
including those of the cell organelles.
 Lecithin may also play an important role in transport of ion across the membranes.
 Phospholipids are of different kinds but all of them contain a glyceryl residue to
which are attached in ester linkage two long chain fatty acid and a phosphorylated
component.
 Sometimes phospholipids grouped under ‘polar lipid’ because they are readily
soluble in polar solvents such as ethanol.
 Phospholipids can be broken down to their residue by the enzyme phosphatidases
which hydrolyze their fatty acids and phosphoric acid ester bonds specifically.

13.  Based upon the types of phosphorylated component of the phospholipids, classified
as :
 Phosphatidyl choline (Lecithin) : This phospholipid has nitrogen containing choline in
its phosphorylated component.
 Phosphotidyl lethanolamine (cephalin) : the phosphorylated component contains
ethanolamine.
Phosphatidyl linositol : The phospholipid contains hexahydric alcohol called inositol in
its phosphorylated component.
Phosphatidyl glycerol : this has glycerol in its phosphorylated component.
Diphosphatidylglycerol (cardiolipin) : It consist of two glycerol residues with their
usual esterifeied fatty acid chains.Both these residues in turns are linked to a common
glyecerol molecule which is phosphorylated on both if its side.

14. Glycolipids
 Glycolipids are lipids with a carbohydrate attached by
a glycosidic (covalent) bond. Their role is to maintain the
stability of the cell membrane and to
facilitate cellular recognition, which is crucial to the immune
response and in the connections that allow cells to connect
to one another to form tissues.
Glycolipids are found on the surface of all eukaryotic cell
membranes, where they extend from the phospholipid
bilayer into the extracellular environment.
Types of Glycolipids
 Cerebrosides : Cerebroside (from cerebro = brain) are glycolipids that are found
primarily in the brain and peripheral (other areas of the body). Nervous Tissue

15. Function : Provide protective coating to each nerve and act as insulator.
 Gangliosides : These glycolipids (glycosphingolipids) are neutral (unchanged).The
gangliosides are acidic in pH and they are the more complex of the glycolipids.
 Sulfoglycosphingolipids : These cerebrosides are called sulfatides, They are simply
cerebrosides with a sulfate residue on the sugar portion of glycolipid.
Occurrance : This particular lipid is found primarily in the medulated nerve fibers.
Functions of Glycolipids
 The glycolipids are an essential part of cell membranes.
Glycolipids also help us to determinate the blood group of an individual.
Glycolipids act as receptors at the receptors at the surface of the red blood cell.
Some viruses, bacteria (Eg : Cholera) use glycolipids on their cell surface as well.
This helps the immune system destroy and clear the pathogen from the body.

16.  Lipids such as sulfolipids and amino lipids.
 Lipoproteins may also be placed in this category
These include fatty acids, glycerol, steroids, other alcohols, fatty aldehydes, and ketone
bodies, hydrocarbons, lipid-soluble vitamins, and hormones. Because they are
uncharged, acylglycerols (glycerides), cholesterol, and cholesteryl esters are termed
neutral lipids. These compounds are produced by the hydrolysis of simple and
complex lipids.
Other complex lipids :
Precursor and Derived Lipids
Some of the different types of lipids are described below in detail.

17. Fatty Acids
 Fatty acids are the simplest form of lipids.
 These are monocarboxylic,straight,unbranhed hydrocarbon chains containing even
number of carbon atoms (between 4-36)
 Fatty acids are also known as acyl group when it is a part of ester.
 Fatty acids are amphipathic in anture.
 The fatty acids may be free or esterified with glycerol to form triglycerides.
Fatty acids are carboxylic acids (or organic acid), usually with long aliphatic tails (long
chains), either unsaturated or saturated.
Saturated Fatty Acids
 Lack of carbon-carbon double bonds indicates that the fatty acid is saturated.
 The saturated fatty acids have higher melting points compared to unsaturated acids of
the corresponding size due to their ability to pack their molecules together thus leading
to a straight rod-like shape.

18.  They have higher melting points.
 They are solid at room temperature.
 Examples- lauric,myristic,palmitic acid etc.
Food Items rich in saturated fats :
 Red meat (beef, lamb, pork)
Whole-fat dairy products (milk, cheese)
Butter.
Ice cream and Lard.
Tropical oils such as coconut and palm oil.
Unsaturated Fatty Acids
 These fatty acids contain one or more double bonds along the length of the
hydrocarbon chain.
 They are liquid at room temperature and have low melting point.
 The commonly used system for designating the position of double bond in
unsaturated fatty acid is the delta numbering system.

19.  Examples – linoleic acid,oleic acid and palmitoleic acid.
 In the naturally occurring unsaturated fatty acid the double bond are in cis
configuration and trans fatty acid are produced by fermentation in the rumen of dairy
animals and are obtained from dairy products and meat.
Food Items rich in saturated fats :
 Plant-based oils such as canola, olive, peanut, safflower, and sesame
Nuts and seeds such as flaxseed, sunflower, and walnuts
Unsaturated fatty acids based upon the number of double bond present :
 Monosaturated Fatty acids : Contain only one double bond per fatty acid.
 Polysaturated Fatty acids : Contain two or more double bonds along the length of the
hydrocarbon chains. They are known as essentaial fatty acids.
 Eg : Linoleic and linolenic fatty acids.

20.  Saturated Fats increases levels of “bad cholesterol” (low density lipoprotein).
 They causes for clogs arteries.
 Unsaturated fats increases levels of “Good Cholesterol” (high density lipoprotein).
 High density lipoprotein helps to break down LDL and can eliminate from the body.
Sterols
 Sterols also known as steroid alcohols.
They are occur naturally in plants, animals, and fungi with the most familiar type of
animal sterol being cholestrol.
Types : Phytosterols – They are plant sterols.
Eg : Campesterol, Sitosterol, and stigmasterol
They block cholesterol absorption sites in the human intestine,thus helping to reduce
cholesterol in humans.
 Zoosterol – They are animal sterol(Cholesterol)
 Ergosterol – They are present in the cell membrane of fungi.

21. Cholesterol
 Cholesterol is a wax-like substance, found only in animal source foods. Triglycerides, LDL,
HDL, VLDL are different types of cholesterol found in the blood cells.
 Cholesterol is an important lipid found in the cell membrane. It is a sterol, which means
that cholesterol is a combination of steroid and alcohol. In the human body, cholesterol is
synthesized in the liver.
 In the cell membrane, the steroid ring structure of
cholesterol provides a rigid hydrophobic structure that
helps boost the rigidity of the cell membrane. Without
cholesterol, the cell membrane would be too fluid.
 It is an important component of cell membranes and
is also the basis for the synthesis of other steroids,
including the sex hormones estradiol and testosterone,
as well as other steroids such as cortisone and vitamin
D.

22. Waxes
 Now we can come across with some other types of lipids :
 Waxes are “esters” formed from long-alcohols and long-chain carboxylic acids.
 Waxes are found almost everywhere. Fruits and leaves of many plants possess waxy
coatings, that can safeguard them from small predators and dehydration.
 Fur of a few animals and the feathers of birds possess same coatings serving as water
repellants.
Roles of fat in our body
 We can just brush up the major roles of fats in our body. Some of the important roles of
fats are mentioned below:
 Fats in the correct amounts are necessary for the proper functioning of our body.
 Many fat-soluble vitamins need to be associated with fats in order to be effectively
absorbed by the body.

23. Triacylglycerol
They also provide insulation to the body.
 They are in efficient way to store energy for longer periods.
Triacylglycerol (trigycerides/fats/neutral fats) are triesters of fatty acids and glycerol.
They are composed of three fatty acids and a glycerol molecules.
Triacylglycerols are of two types :
i) SimpleTriacylglycerols : These contains single type of fatty acids.
ii) Mixed Triacylglycerols : These contains two or more different kind of fatty acid.
Example of an unsaturated fat
triglyceride (C55H98O6). Left
part: glycerol; right part, from top to
bottom: palmitic acid, oleic
acid, alpha-linolenic acid.

24.  Triacylglycerols are non polar, hydrophobic in nature and a major form of stored lipids.
These molecules contain fatty acids of various length and they be saturated or
unsaturated.
 They can be distinguished as fat and oil on the basis of physical state at room
temperature.
 Triglycerides are the main constituents of body fat in humans and other vertebrates, as
well as vegetable fat.
They are also present in the blood to enable the bidirectional transference of adipose fat
and blood glucose from the liver, and are a major component of human skin oils.
 Triglycerides cannot pass through cell membranes freely. Special enzymes on the walls of
blood vessels called lipoprotein lipases must break down triglycerides into free fatty acids
and glycerol. Fatty acids can then be taken up by cells via the fatty acid transporter (FAT).

25. Role of Triacylglycerol in diseases
 In the human body, high levels of triglycerides in the bloodstream have been linked
to atherosclerosis, heart disease and stroke. However, the relative negative impact of
raised levels of triglycerides compared to that of LDL : HDL ratios is as yet unknown.
 The risk can be partly accounted for by a strong inverse relationship between
triglyceride level and HDL-cholesterol level. But the risk is also due to high triglyceride
levels increasing the quantity of small, dense LDL particles.
The National Cholesterol Education Program has set guidelines for triglyceride levels:
These levels are tested
after fasting 8 to 12 hours.
Triglyceride levels remain
temporarily higher for a
period after eating.

26. Reducing triglyceride levels
 Weight loss and dietary modification are effective first-line lifestyle modification
treatments for hypertriglyceridemia. For people with mildly or moderately high levels of
triglycerides, lifestyle changes, including weight loss, moderate exercise and dietary
modification, are recommended. This include restriction of carbohydrates and fat in
the diet and the consumption of omega-3 fatty acidsfrom algae, nuts, and seeds.
 Medications are recommended in those with high levels of triglycerides that are not
corrected with the aforementioned lifestyle modifications, with fibrates being
recommended first Omega-3-carboxylic acids is another prescription drug used to treat
very high levels of blood triglycerides.

27.  So, lipids help store the energy in the form of fat molecules in the body to use later.
 Lipids are present in every cell of the human body and are the main part of the cellular
membrane. It prevents the cells from being leaky by surrounding them the perfect way.
 Lipids are also essential for the human body as they are a part of many hormones.
They play a major role in regulating your growth and how your body works on a daily
basis. The hormones of which lipids are an essential part include.
 Lipids also play an important part in the digestion of food. It is used to make bile acids
n the stomach which is essential for dissolving fat from the food you eat. This is essential
for the process of normal digestion of food and the absorption of fat soluble vitamins.
They are also essential for the transportation of fatty acids in the body.
Lipids are the building blocks of cells in our body. Therefore, it is necessary to include
lipid rich food in our daily diet. Always increase intake of unsaturated fatty acids.It is
vital to maintain a balanced diet for a healthy life.
CONCLUSION
Importance of lipids in Human body
2