Page 55 - Biology_F5

Biology for Advanced Level Secondary Schools

(b) Compound lipids or heterolipids contain fatty acids, alcohols, and other
These are esters of fatty acids with components, such as phosphorous,
alcohols that possess additional groups amino-nitrogen and carbohydrates, as
which may be derived from acids other shown in table 1.4.
than fatty acids. The compound lipids

FOR ONLINE READING ONLY
Table 1.4: Compound lipids
Phospholipids or These contain a phosphate group. Their glycerol forms ester bond with
phosphatides phosphoric acid and two fatty acids (Figure 1.30). They usually contain
one hydrophilic head and two hydrophobic tails. They are called polar
lipids and are amphipathic in nature

Glycolipids Glycolipids are compound lipids with carbohydrates. These lipids
include certain structurally related compounds comprising gangliosides,
sulpholipids, and sulfatides groups

Sphingolipids or Sphingolipids occur mostly in the cells of the brain. They do not
phosphosphingosides contain glycerol in their molecules; instead, they contain amine alcohol
(sphingosine or sphingol). For instance, the myelin sheath of the
nerve fibres contains a lipid known as sphingomyelin, which contains
sphingosine and phospholipids in its molecules. Terpenes are mostly
found in plants. Examples of terpenes are natural rubber and gern oil

Glycerol
Hydrocarbons (fatty acid tails) Hydrophilic
H O head

H C O C
O

H C O C
O O Hydrophobic
tails
O P O C O C H

O H
Figure 1.30: Structure of the phospholipid

c) Derived lipids and they are non saponifiable and not
Derived lipids are substances derived from hydrolysed on heating. They are widely
simple and compound lipids by hydrolysis. distributed in animals, where they are
The most common derived lipids are associated with physiological processes.
steroids, terpenes, and carotenoids. Examples of steroids include hormones,
Steroids: These do not contain fatty acids such as oestrogen, progesterone and
testosterone.

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