Lipids are organic compounds that are insoluble in water but soluble in organic solvents. They include fats, oils, waxes, sterols and phospholipids. Fats and oils are triglycerides composed of glycerol and fatty acids. Fatty acids are classified as saturated, monounsaturated, or polyunsaturated. Phospholipids are a major component of cell membranes and lipoproteins transport lipids in the blood. Lipids serve important functions as energy stores, insulation, and as precursors to other compounds like hormones and vitamins.

1. Lipids
M. ShoaibAslam
Lecturer

2. Contents
Classes of Lipids
Fatty Acids and Triglycerides
Saturated, Monounsaturated, and Polyunsaturated Fatty Acids
Classification of Lipoproteins
RDA for fat with food sources
Omeg-3 fatty Acids & Cardiovascular disease
Trans Fats and Chronic Diseases
Digestion, Absorption and Metabolism

3. Introduction
Defination
“A lipid is an organic substance found in living
systems that is insoluble in water but is soluble
inorganicsolvents”
• The biological functions of lipids are as diverse as theirchemistry
• Lipids vary widely in their structures.
• They have mostly C,H and some have a few polar atoms/ functional
groups.

4. Classification

5. Fats & Oils
Lipids include:
• Fats and oils
• Steroids
• Fats & oils make up 95% of the nutritional lipids, the
other 5% are steroids.
• Fats and oils are the principal stored forms of energy in
many organisms

6. Difference between fats and
oils
• Fats and oils are triglycerides with varying
degrees of saturated and unsaturated fatty
acids
– Fats – generally solid at room temperatures
and high in saturated fatty acids
– Oils –generally liquid at room temperatures
and low in saturated fatty acids

7. Classification of Lipids
Simple Lipids
• These are esters of fatty acids with various alcohols
• They include neutral fats and waxes
Neutral Fats or Triacylglycerols (tags):
• TAGs are the esters of the fatty acids with glycerol
• The fatty acids moiety in lipid esters is called ‘acyl’group
• TAGs are the major storage and transport form of lipids
• TAGs with different fatty acid compositions are known as
mixed TAGs

8. Triglycerides Are Esters of
Glycerol and Fatty Acids
condensation
reaction
Glycerol
"backbone" is a
water-soluble
alcohol
Fatty Acids are chains of carbon atoms
with a methyl (-CH3) group at one end and
a carboxylic acid (-COOH) group at the
other
Glycerol + 3 Fatty Acids Triglyceride + 3 water molecules

9. Triglycerides Are Esters of
Glycerol and Fatty Acids

10. A. Triacylglycerols (tags):
Fatty Acids
• These are organic acids that occur in nature and
aliphatic monocarboxylic acid made up of hydrocarbon
• They are the major component of lipids
• Chain length of lipids forming fatty acids range from 4 to
24 carbon atoms
• Fatty acids which occur in neutral fats usually contain
even number of carbon atoms

11. Classification of Fatty Acids

12. Classification of Fatty Acids

13. Fatty Acids
Saturated Fatty Acids:
• These fatty acids do not contain double bond e.g. butyric
acid, caproic acid, palmitic acid, stearic acid etc.
• Saturated fatty acids having less than 10 carbon atoms
are liquid at room temperature and are volatile

14. Fatty Acids

15. Fatty Acids
• Saturated fatty acids, especially palmitic and stearic
acids are found in animal products such as cream,
cheese, butter, other whole milk dairy products and fatty
meats which also contain dietary cholesterol.
• Certain vegetable products have high saturated fat
content, such as coconut oil and palm kernel oil.
• Many prepared foods are high in saturated fat content,
such as pizza, dairy desserts and sausage.

16. Fatty Acids

17. Un Saturated Fatty Acids:
• These fatty acids consist double bonds.
• These are further classified according to degree of their
unsaturation i.e monounsaturated and polyunsaturated
fatty acids
Monounsaturated Fatty Acids:
• Contain only one double bond e.g. oleic acid, found in
nearly all fats
• Monounsaturated fats are good fats.

18. Fatty Acids
Polyunsaturated Fatty Acids:
• These contain more than one double bond
• Three polyunsaturated fatty acids having biological
importance PUFA’s are not synthesized in the body are
“essential fatty acids and therefor should be taken in the
diet
• Oils contain significant quantity of polyunsaturated fatty
acids
• Oil from corn, wheat germ, peanut and soya bean

19. Fatty Acids
Monounsaturated Fatty Acids:
• A diet high in MUFA can reduce blood cholesterol levels,
lowers risk of heart disease, stroke and breast cancer,
reduces pain in rheumatoid arthritis and helps in weight
loss.
• Foods which contain MUFA (Oleic acid) are avocados,
olive oil, peanut butter and peanut oil. It is also known as
omega-9 fatty acid.

20. Polyunsaturated Fatty Acids
Omega-3:
• It is also called n−3 fatty acids with a double bond (C=C) at the
third carbon atom from the end of the carbon chain.
• The three types of omega−3 fatty acids
involved in human physiology are
• α-linolenic acid (ALA)
• Eicosapentaenoic acid (EPA)
• Docosahexaenoic acid (DHA)

21. Polyunsaturated Fatty Acids
Omega-3:
• The health benefits of omega-3 fatty acids are immense
• They have been proven effective in the treatment and
prevention of hundreds of medical conditions which
includes high cholesterol,
• Depression
• Anxiety
• Cancer
• Diabetes mellitus,
• Arthritis and cardiovascular diseases

22. Polyunsaturated Fatty Acids

23. Polyunsaturated Fatty Acids

24. Polyunsaturated Fatty Acids

25. Polyunsaturated Fatty Acids
Omega-6:
• Omega-6 fatty acids (also referred to as n-6 fatty acids)
• A family of pro- inflammatory and anti-inflammatory
polyunsaturated fatty acids that have in common a final carbon-
carbon double bond in the n-6 position, that is the sixth bond,
counting from the methyl end.
• Omega-6 fats, also known as linoleic acid, are available only in
food.
• The human body cannot make them, so they are considered
essential fats. They support brain function, bone health, reproductive
health, hair growth and regulation of metabolism.
• Good sources of linoleic acid include vegetable oils.

26. Classification
On the Basis of Requirement
1. Essential fatty acids
•Fatty acids which are essential to be taken in our diet because
they cannot be synthesized in our body are known as essential
fatty acids.(eg.) Linoleic, linolenic and arachidonic acids.
2. Non-essential fatty acids
•Non-essential fatty acids are those which can be synthesized by
the body and which need not be supplied through the diet.
Palmitic acid, oleic acid and butyric acid are examples of non–
essential fatty acids.

27. Cis Fats
• When a mono- or polyunsaturated oil is hydrogenated, it is not
possible to control where the hydrogen atoms are added to the
structure.
• If both hydrogen atoms are added to the same side of the
structure, it is called a "Cis" fat. Cis (means ‘on the sameside’)

28. Trans Fats
• Trans fats.
• Trans fats are unique, in that they are unsaturated lipids that
function much like their saturated counterparts.
• While small amounts of trans fats are naturally occurring in
some foods, such as butter, they primarily are produced
through partial hydrogenation of unsaturated oils, such as
soybean oil.

29. Cis &Trans Fats

30. Trans Fat & CVD
•But the price the consumer pays for the benefit of the food
industry is a cardiovascular risk, in the form of trans fats,
which is why the government required the amount of trans
fats to be listed on labels starting in January 2006.
•Even with the same caloric intake (including fat calories)
in two groups, the group with the higher trans fats intake
gained more weight.
•Giving the “apple” shape, which has been implicated in
giving rise to an increased cardiovascular risk.
•The bad news about trans fats has been gathering for
years, but commercial interests would rather bury the
information

31. Compound Lipids
2.1 Phospholipids
• The compound lipids contain, in addition to fatty acids and
glycerol, some other organic compounds.
Phospholipids: These contain phosphoric acid and a nitrogenous
base in addition to fatty acids and glycerol
(e.g.)Lecithin and cephalin

32. Compound Lipids
Phospholipids
• Phospholipids make up the basic structure of
a cell membrane.
• A single phospholipid molecule has two
different ends: a head and a tail. The head
end contains a phosphate group and is
hydrophilic. This means that it likes or is
attracted to water molecules.
• The tail end is made up of two strings of
hydrogen and carbon atoms called fatty acid
chains. These chains are hydrophobic, or do
not like to mingle with water molecules.

33. Compound Lipids
Phospholipids
• This arrangement of phospholipid molecules
makes up the lipid bilayer
• The hydrophilic phosphate heads are always
arranged so that they are near water.
• Watery fluids are found both inside a cell
(intracellular fluid) and outside a cell
(extracellular fluid). The hydrophobic tails
of membrane phospholipids are organized in
a manner that keeps them away

34. 2. Compound lipids
(i) Phospholipids
• Phospholipids and sterols are major structural components of
biological membranes as well as in serum lipoproteins, bile
•They play an important role in electron transport, oxidative
phosphorylation and energy linked transport of ions across
membranes.

35. 2. Compound lipids
Chylomicron
Chylomicron:
• A small fat globule composed
of protein and lipid (fat).
Chylomicrons
• Found in the blood
• serve to transport fat intestine
to the liver and to adipose (fat)
tissue.

36. 2. Compound lipids
LDL
• LDL (low-density lipoprotein): A molecule that is a
combination of lipid (fat) and protein. Lipoproteins are the
form in which lipids are transported in the blood.
• Low-density lipoprotein (LDL) transports cholesterol from the
liver to the tissues of the body.
• LDL cholesterol is therefore considered the "bad" cholesterol.

37. 2. Compound lipids
HDL
• HDL cholesterol: High density lipoprotein cholesterol.
Lipoproteins, which are combinations of fats (lipids) and
proteins, are the form in which lipids are transported in the
blood.
• HDLs transport cholesterol from the tissues of the body to the
liver.
• HDL cholesterol is therefore considered the 'good' cholesterol:
The higher the HDL cholesterol level, the lower the risk of
coronary artery disease..

38. 2. Compound lipids

39. Functions of Lipids
• They are the components of cells and cell organelles
membrane.
• They are the major storage forms of energy
• They are good emulsifying agents
• In the body, 1 gram of fat produces about 9 kilocalories
• They have a high satiety value
• Lipids are the precursors of other important compounds e.g.
cholesterol, prostaglandins and ketone bodies.
• Cholesterol is the precursor of bile acids and steroid hormones.
• 7-dehydrocholesterol is the precursor of vitaminD3.
• Prostaglandins have hormone like actions in the body.

40. Functions of Lipids
• Ketones bodies act as a reserve fuel.
• Lipids provide insulation to the nervous system against
atmospheric heat and cold.
• They provide anatomical stability to the internal organs and
protect them against physical shocks.
• Lipids under the skin prevent excessive loss of water and
electrolytes.
• They help in transportation of fat soluble vitamins and other
fat soluble compounds across the membrane.
• They protect the body against the injurious effects of water
soluble substances.

41. Functions of Lipids
• The fats that we get from food are vital to good health.
• They provide energy and essentialfatty acids for healthy skin
and important hormone like substances.
• Fats also carry and help the body absorb the fat-soluble
vitamins A, D, E and K.
• What’s more, dietary fats help us feel satisfied following
meals.