Lipids are fatty compounds that perform a variety of functions in your body.

1. Lipid’s
1

2. Specific Learning objectives
At the end of the lecture students will be able to
• Define lipids.
• Classify lipids.
• Describe the functions of lipids.

3. INTRODUCTION
• The word lipid is derived from a Greek word “lipos” which
means Fat.
• Biological lipids are a chemically diverse group of organic
compounds which are insoluble in water.
• They are 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-) in their structures.

4. Cont…
• Lipids are of great importance to the body as the chief
concentrated storage form of energy, besides their role in
cellular structure and various other biochemical
functions.
• As such, lipids are a heterogeneous group of compounds.

5. DEFINITION OF LIPIDS
Lipids may be regarded as organic substances relatively
insoluble in water, soluble in organic solvents (alcohol,
ether etc.), actually or potentially related to fatty acids and
utilized by the living cells.

6. FUNCTIONS OF LIPIDS
They serve as a storage form of metabolic fuel. (fatty acid,
Triacyglycerol).
They serve as a transport form of metabolic fuel.(free
fatty acid, triglyceride and cholesterol ester).
They provide the structural components of
membranes(phospholipids, glycolipids, galactolipids,
sphingolipids).

7. Cont….
They have protective functions in bacteria, plants,
insects, and vertebrates, serving as a part of the
outer coating between the body of the organism and
the environment.
It serve as pigment (carotene), hormones(vitamin A &
D), signaling molecules(eicosanoids,
phosphatidylinositol, steroid hormone)
cofactors(vitamin E, K and lipid quinones) detergent
(bile salt).

8. Cont….
Fat serves as an efficient source of energy when stored in
adipose tissue
Necessary for absorption of fat soluble vitamins
Insulating material in the subcutaneous tissues
Protect the organs by providing padding around them

9. Cont….
Lipoproteins & glycoproteins – essential for
maintaining cellular integrity
Phosphatides of platelets – production of
thromboplastin activity in blood clotting
Major structural components of membranes
Activators of enzymes
Fat & proteins are imp. Cellular constituents

10. Cont….
Imp. Dietary constituents – fat soluble vitamins & Essential FA
found in fats of natural foods
Bile salts derived from cholesterol – emulsifying agents
Nervous tissue is rich in lipids
Steroid hormones – physiologic activity
Electron Transport Chain – Phospholipids in mitochondria

11. Cont….
They are the concentrated fuel reserve of the
body (triacylglycerols).
Lipids are the constituents of membrane
structure and regulate the membrane
permeability (phospholipids and cholesterol).
They serve as a source of fat soluble vitamins
(A, D, E and K).

12. Cont….
Lipids are important as cellular
metabolic regulators (steroid hormones
and prostaglandins).
Lipids protect the internal organs, serve
as insulating materials and give shape
and smooth appearance to the body

13. CLASSIFICATION OF LIPIDS
Simple
lipids
Complex
lipids
Derived
lipids
Miscellaneous
lipids

14. Simple Lipids
• Simple lipids are the esters of fatty acids with
alcohols.
• Simple lipids includes fats , oils and waxes.
• These simple lipids are derivatives of lipid like
substances call fatty acids.
• These are mainly of two types
a) Fats and oils (triacylglycerols).
b) Waxes

15. Cont….
(a) Fats and oils (triacylglycerols) :
• These are esters of fatty acids with glycerol.
• The difference between fat and oil is only physical.
Thus, oil is a liquid while fat is a solid at room
temperature.

16. Cont….
b) Waxes
• Esters of fatty acids (usually long chain) with
alcohols other than glycerol.
• These alcohols may be aliphatic or alicyclic.
• Cetyl alcohol is most commonly found in waxes.
• Waxes are used in the preparation of candles,
lubricants, cosmotics, ointments, polishes etc.

17. Complex (or compound) lipids :
• These are esters of fatty acids with alcohols
containing additional groups such as phosphate,
nitrogenous base, carbohydrate, protein etc.
• They are further divided as follows
• Phospholipids
• Glycolipids
• Lipoproteins
• Other complex lipids

18. Cont….
(a) Phospholipids- They contain phosphoric acid and
frequently a nitrogenous base. This is in addition to
alcohol and fatty acids.
i. Glycerophospholipids : These phospholipids contain
glycerol as the alcohol. e.g., lecithin, cephalin.
ii. Sphingophospholipids : Sphingosine is the
alcohol in this group of phospholipids e.g.,
sphingomyelin.

19. Cont….
b) Glycolipids- These lipids contain a fatty acid,
carbohydrate and nitrogenous base. The alcohol is
sphingosine, hence they are also called as
glycosphingolipids. Glycerol and phosphate are
absent e.g., cerebrosides, gangliosides

20. Cont….
c) Lipoproteins : Macromolecular complexes of lipids
with proteins.
d) Other complex lipids : Sulfolipids, aminolipids and
lipopolysaccharides are among the other complex
lipids.

21. Derived lipids
• These are the derivatives obtained on the
hydrolysis of group 1 and group 2 lipids which
possess the characteristics of lipids.
• These include glycerol and other alcohols, fatty
acids, mono- and diacylglycerols, lipid (fat) soluble
vitamins, steroid hormones, hydro carbons and
ketone bodies.

22. Miscellaneous lipids
• These include a large number of compounds
possessing the characteristics of lipids
e.g., carotenoids, squalene, hydrocarbons such as
pentacosane (in bees wax), terpenes etc.

23. Neutral Lipids
The lipids which are uncharged are referred to as
neutral lipids. These are mono-, di-, and
triacylglycerols, cholesterol and cholesteryl esters

24. Expected Questions
Essay/ Situational type
• Define lipids and classify it.
Short
• Describe the functions of lipids.
Very Short
• Define lipids.

25. References
• Jacob Anthikad, Biochemistry for nurses
• Pankaja Naik, Essentials of Biochemistry
• Satyanarayan, Essentials of Biochemistry
• A. C. Deb, Biochemistry

26. THANK YOU