Page 54 - Biology_F5

Cytology

1.4.2 Lipids Types of lipids
In 1943, William R. Bloor proposed the
Task 1.5
Search for information from the library classification of lipids basing on their
and internet sources and prepare a brief chemical composition as simple lipids,
report about: compound lipids, and derived lipids.
FOR ONLINE READING ONLY
(a) properties of lipids
(b) biochemical tests for lipids. (a) Simple lipids or homolipids
These are esters of fatty acids and various
Lipids are made up of carbon, hydrogen, alcohols. Such lipids include fats and
and oxygen in which the content of oxygen oils (whose alcohol is glycerol) and
is always smaller compared to carbon and waxes, which contain alcohols higher
hydrogen. Lipids are important constituents than glycerol. Fats differ from oils in that

of the diet, because they are the source of they contain fatty acids with saturated
high energy value. Natural fats and oils are hydrocarbon chain. In oils, fatty acids
compounds of glycerol and fatty acids. They contain unsaturated hydrocarbon chains.
are esters, which are formed as the result At room temperature, oil is liquid, while
of the reaction between organic acids and fat is solid. Fatty acids have a general
alcohols. formula of CH (CH ) COOH where 'n' is
3 2 n
a whole number. Stearic acid is a common
Formation of lipids fatty acid in animals’ adipose tissue. The

Lipids are esters formed by the reaction fats and oils are triglycerides, formed by
between fatty acids and alcohols. In simple the combination of one trihydroxyl alcohol
lipids, such as fats and oils, the alcohol (glycerol), and three fatty acid molecules.
involved in the reaction is glycerol. The In this process, three molecules of water
formation of lipids is by condensation are lost and the ester bond is formed
reaction; therefore, a molecule of water (Figure 1.29).
is lost. This forms a covalent bond called
ester bond.

Ester bond
H O H O
H - C - O - H H - O - C- R H C O C R
O O
H - C - O - H H - O - C- R H C O C R + 3H 0
2
O O
H - C - O - H H - O - C- R H C O C R
H H
Glycerol + 3Fatty acids Triglyceride + 3Water

Figure 1.29: Formation of triglyceride

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