Fatty acids are long chain organic acids that are the building blocks of lipids. They contain a carboxyl group and a long hydrocarbon tail. There are over 100 different types of fatty acids that can be classified as either saturated or unsaturated. Saturated fatty acids have no double bonds between carbon atoms, while unsaturated fatty acids contain one or more double bonds. Lipids include fats, waxes, phospholipids, glycolipids and steroids. They serve important functions like energy storage, insulation, cell structure and transport. The main classes of lipids are simple lipids like triglycerides and waxes, and complex lipids including phospholipids, glycolipids and steroids.

1. Fatty acids
Fatty acids long chain organic acids 2-24 carbon atoms.
single carboxyl group and a long, nonpolar hydrocarbon tail.
building block units of lipids.

2. Fatty acids
Amphipathic molecule
Diverse structures (>100 different
types)

3. Classification of Fatty acids
1. Saturated Fatty acids
2. Unsaturated Fatty acids

4. Classification of Fatty acids
1. Saturated Fatty acids:
derivative of acetic acid  at least 4 carbon atom.
All carbon  fully saturated no double bond is .
2. Unsaturated Fatty acids:
double bonds between any two carbon atoms
. Generally double bonds C-9 and C-10.
•PUFA:
more than 2 double bonds Polyunsaturated fatty acids
(Polyethenoid).
E.g linoleic acid, linolenic acid and arachidonic acid fatty
acids (EFA)

5. Lipids
esters of fatty acids or are substances such
Esters
heterogenous compound, greasy in nature insoluble in water but
soluble in organic solvents

6. Occurrence of Lipids
Abundant plants, animal and microorganism  major
component  Biological membrane
Lipid  huge amount as triglycerides in adipose tissue of
animals and in cytoplasm of plants.

7. Functions of Lipids
1. Source of energy:
2. Storage of energy:
3. Heat insulation and Mechanical protection:
4. Structural components of cells:
5. transport form

8. Functions of Lipids
4. Structural components of cells:
5. transport form

9. Classification of Lipids

10. Classification of Lipids
I. Simple Lipids
Esters of fatty acids  various alcohols:
(a) Neutral fats (Triacylglycerol, TG):
triesters of fatty acids  glycerol.
(b) Waxes: Testers of fatty acids  higher monohydroxy
aliphatic alcohols.

11. Classification of Lipids
2.Complex lipids: Esters of fatty acids
containing other groups
(a) Phospholipids
substituted fats fatty acid and alcohol
+ a phosphoric acid residue, +
nitrogenous base +other
substituents.
(i) Glycerophospholipid: glycerol 
alcohol. e.g. ,lecithin, cephalin.
(ii) Sphingophospholipids: Sphingosine
 the alcohol e.g. sphingomyelin.

12. Classification of Lipids
(b) Glycolipids
With carbohydrate moiety.
sphingosine or sphingol + nitrogenous + fatty acids
No phosphoric acid and glycerol.
These are of two types:
• Cerebrosides
• Gangliosides

13. Classification of Lipids
C. Steroids
With cyclopentan ring system.
The basic structure of steroids is a four-ring hydrocarbon.
Three parts, Polar head, rigid planar steroid ring and nonpolar
hydrocarbon tail.

14. Classification of Lipids
Importance of cholesterol
• component of some cell membranes and of plasma
lipoproteins.
•precursor of many other biologically important steroids
•
•sterol of higher animals abundant in nerve tissues and in
gallstones.
•High blood atherosclerosis.