Chemistry Reference
In-Depth Information
FIGURE 8.10
Examples of simple and complex lipids.
8.3.1 Fatty Acids
A discussion of lipids requires some knowledge of the fatty acids which are
a major part of complex lipid structures. As
Table 8.1
shows, fatty acids are
carboxylic acids which have long unbranched hydrocarbon chains. Because of
the biosynthetic routes that they come from, the acids usually contain even
numbers of between 12 and 26 carbon atoms.
Fatty acids are classified as saturated or unsaturated, depending on the presence
or absence of C
]
C double bonds in the hydrocarbon chain. Any C
]
C double
bonds that are present, are almost always in the form of the
cis
stereoisomer.
About 40 fatty acids occur in nature. In
Table 8.1
, palmitic and stearic are the
most common examples for fully saturated fatty acids. Oleic and linoleic are the
most common examples for unsaturated fatty acids.
Table 8.1
Selected Common Fatty Acids
Common
Name
Structural Formula
IUPAC Name
M.P. (°C)
CH
3
(CH
2
)
10
CO
2
H
Lauric
Dodecanoic
43
CH
3
(CH
2
)
12
CO
2
H
Myristic
Tetradeconoic
55
CH
3
(CH
2
)
14
CO
2
H
Palmitic
Hexadecanoic
63
CH
3
(CH
2
)
16
CO
2
H
Stearic
Octadecanoic
70
CH
3
(CH
2
)
7
CH
]
CH(CH
2
)
7
CO
2
H
Oleic
cis
-9-Octadecenoic
14
CH
3
(CH
2
)
4
(CH
2
CH
]
CH)
2
(CH
2
)
7
CO
2
H
Linoleic
cis, cis
-9,12-Octadecadienoic
−5
CH
3
(CH
2
CH
]
CH)
3
(CH
2
)
7
CO
2
H
Linolenic
cis, cis, cis
-9,12,15-Octadecatrienoic
−11
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