This Presentation is made for S.Y.Bsc. Students. This presentation includes the structure of Lipids and biological significance of lipids.

1. LIPIDS
By: Dr. MohammedAzim Bagban
Asst. Professor, Microbiology,
C. U. Shah Institute of Science
MI 201
Unit-1

2. Lipids definition
• Lipids are a heterogeneous group of organic compounds
that are insoluble in water and soluble in non-polar
organic solvents like chloroform & ether.
• They naturally occur in most plants, animals,
microorganisms and are used as cell membrane
components, energy storage molecules, insulation, and
hormones.
2

3. Types of Lipids
3

4. 4

5. Classification of Lipids
Lipids can be classified according to their hydrolysis products
and according to similarities in their molecular structures.
Three major subclasses are recognized:
1. Simple lipids
2. Complex lipids
3. Derived lipids:
5

6. 1. Simple lipids
(a) Fats and oils which yield fatty acids and glycerol upon hydrolysis.
(b) Waxes, which yield fatty acids and long-chain alcohols upon
hydrolysis.
 Fats and Oils
• Both types of compounds are called triacylglycerols because they
are esters composed of three fatty acids joined to glycerol,
trihydroxy alcohol.
• The difference is on the basis of their physical states at room
temperature. It is customary to call a lipid a fat if it is solid at 25°C,
and oil if it is a liquid at the same temperature.
• These differences in melting points reflect differences in the
degree of unsaturation of the constituent fatty acids.
6

7. Waxes
• Wax is an ester of long-chain alcohol (usually mono-
hydroxy) and a fatty acid.
• The acids and alcohols normally found in waxes have chains
of the order of 12-34 carbon atoms in length.
• Waxes are water-insoluble due to the weakly polar nature
of the ester group.
7

8. Some Unique Simple lipids
Terpenes are unique lipids
• Now that we understand what lipids are, we can look at terpenes.
Terpenes are non-saponifiable lipids, or simple lipids, and do not
contain fatty acids.
• Rather, terpenes have an isoprene base and are categorized
depending on the number of isoprene units it has. Terpenes with
two isoprene units are called monoterpenes, three units are
sesquiterpenes, four units are diterpenes, five units are
sesterterpenes, and six are triterpenes.
8

9. Steroids
• Steroids: A group of plant and animal lipids that
have the tetracyclic ring structure shown below.
9

10. • The fusion of rings is trans and each atom or group at
a ring junction is axial.
• The pattern of atoms or groups along the ring
junctions is nearly always trans-anti-trans-anti-trans.
• The steroid system is nearly flat and quite rigid.
• Most have axial methyl groups at C-10 and C-13.
• Features common to steroids.
10

11. Examples of Steroids
Cholesterol
Testosterone Androsterone Cortisone
Progesterone Estrone (estrogen)
11

12. 2. Complex lipids
According to the chosen classification, they contain frequently
three or more chemical identities (i.e. glycerol, fatty acids and
sugar, one long chain base, one nucleoside, one fatty acid and
one phosphate group…) and have polar properties. Some contain
only two components but including a sugar moiety.
12

13. They can be classified into four main groups:
PHOSPHOLIPIDS
Lipids with a phosphate
residue, one glycerol, or
an aminoalcohol or a
fatty alcohol, and with
one or two fatty chains
(exceptionally one
inositol group, two
phosphates or four fatty
chains)
GLYCOLIPIDS
Lipids containing a
glycosidic (carbohydrates)
moiety with a glycerol or
an aminoalcohol and with
fatty chain(s) (sometimes
with one or more
phosphate groups)
13

14. NUCLEOLIPIDSLIPOPROTEINS
• Lipids without
phosphate group
and containing one
or more amino
acids linked to long-
chain alcohol and
acids.
• Important structure
of bacterial cell
wall
Lipids containing a
nucleobase, or a
nucleoside, or a
nucleotide or an
oligonucleotide
14

15. Fatty Acids
• Fatty acid: A long, unbranched chain carboxylic acid.
• Nearly all have an even number of carbon atoms, most between 12 and
20 in an unbranched chain.
• The three most abundant are palmitic acid, stearic acid and oleic acid.
• In most naturally occurring unsaturated fatty acids, the cis isomer
predominates; the trans isomer is rare.
• Unsaturated fatty acids have lower melting points than their saturated
counterparts; the greater the degree of unsaturation, the lower the
melting point.
15

16. • At room temperature most saturated fatty acids are
solids and most unsaturated fatty acids are liquids.
16

17. Fats
• Fats are fatty acids esters of glycerol, where fatty acids are attached
to glycerol with ester linkage.
• Fats are one of the three main macronutrients, along with
carbohydrates and proteins.
• Fat molecules consist of primarily carbon and hydrogen atoms and
are therefore hydrophobic and are soluble in organic solvents and
insoluble in water. Examples include cholesterol, phospholipids, and
triglycerides.
17

18. Triglycerides
• Triglyceride: An ester of glycerol with three fatty acids.
• Saturated triglycerides are more commonly known as
fats.
• Unsaturated triglycerides are more commonly known as
oils.
18

19. Properties of Fats
• Non-polar in nature make it water insoluble and hydrophobic
• Natural soaps are prepared by boiling lard or other animal fat with
NaOH (lye), in a reaction called saponification (Latin, sapo, soap)
to have the fat undergo base-catalyzed ester hydrolysis.
• Soap is the (sodium) salt of a fatty acid.
•
19

20. • Soaps clean by acting as emulsifying agents.
• The long hydrophobic hydrocarbon chains of soaps
are insoluble in water and tend to cluster in such a
way as to minimize their contact with water.
• The polar hydrophilic carboxylate groups remain in
contact with the surrounding water molecules.
• Driven by these two forces, soap molecules
spontaneously cluster into micelles.
20

21. • Micelle: A spherical arrangement of organic
molecules in water clustered so that their hydrophobic
parts are buried inside the sphere and their
hydrophilic parts are on the surface of the sphere and
in contact with water.
21

22. • When soap is mixed with water-insoluble grease, oil,
and fat stains, the nonpolar parts of the soap micelles
“dissolve” nonpolar dirt molecules and they are
carried away in the rinse water.
22

23. Biological Significance
Potential source of
energy
Vital role in the
membrane
structure of cells
Many lipids such
as steroids act as
hormones &
regulators
Serve as cellular
reserves of food
Serve as source of
FAT soluble
vitamins like A,D,E
& K
23

24. • http://www.phys.sinica.edu.tw/TIGPNANO/Course/2006_Spring/classnotes/Nan
obio%20031006.pdf
• http://www.notesonzoology.com/lipids/lipids-definition-classification-an-
functions-biochemistry/3510
• https://alevelnotes.com/Lipids/58
• Smith, C. M., Marks, A. D., Lieberman, M. A., Marks, D. B., & Marks, D. B. (2005).
Marks’ basic medical biochemistry: A clinical approach. Philadelphia: Lippincott
Williams & Wilkins.
• http://cyberlipid.gerli.com/description/complex-lipids
• https://www.rndsystems.com/research-area/steroid-hormones-and-bioactive-
lipids
24