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Monounsaturated fatty acids
contain one double bond
usually liquid at room temperature
found primarily in plant foods like avocados,
olives and nuts and in various vegetable oils
like olive oil and canola oil
Common monounsaturated fatty acids are:
palmitoleic acid
oleic acid
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Polyunsaturated fatty acids
contain two or more double bonds
like monounsaturated fat, is usually liquid
at room temperature
polyunsaturated fat is mostly found in plantfoods like most nuts and in vegetable oils
like corn, soybean and safflower
Common polyunsaturated fatty acids are:
linoleic acidlinolenic acid
arachidonic acid
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TO DESCRIBE THE UNSATURATED FATTY ACIDS,
TWO WAYS ARE OFFERED:
The chemist's terminology:
The carbon atoms are counted from the carboxyl
group which put the emphasis on the double bond
closest to this group (D-notations)
As an example: 18:2 (9,12 or cis-9, cis-12-
octadecadienoic acid, the trivial name: linoleic
acid
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The biochemist's and physiologist's terminology:
Holman RT proposed in 1964 a new numberingsystem for the unsaturation of fatty acids, the "omeganomenclature".
The double bonds are counted from the methyl groupdetermining the metabolic family, noted by wx (w forthe terminal carbon) or better n-x (n for the total
number of carbon, x being the position of the distaldouble bond)
Thus, linoleic acid or cis-9, cis-12-octadecadienoic acidis also named in the shorthand nomenclature 18:2 (n-6). This compound has 18 carbon atoms, 2 double
bonds and 6 carbon atoms from the last double bondto the terminal methyl group. In the old literature itwas designated 18:2w6.18-6=12, 12-3=9, hence (9,12.
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NOMENCLATURE
Fatty acids can be named in many ways:
symbolic name: given as x:y (( a,b,c) where x is
the number of Cs in the chain, y is thenumber of double bonds, and a, b, and c are
the positions of the start of the double bonds
from C1 - the carboxyl C
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Example:y OLEIC ACID 18:1( or [
Oleic acid contains 18 carbon atoms and a double
bond between positions9
and 10, indicated by18:1(
The number 18 indicates the number of carbon
atoms, 1 indicates the number of double bonds
and the ( and superscript indicate the position of
double bond
Fatty acids may also be classified by the distance
of the first double bond from the [-carbon
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systematic name using IUPA
Cnomenclature. The systematic name
gives the number of Cs (e.g.
hexadecanoic acids for 16:0)
If the fatty acid is unsaturated, the
base name reflects the number of
double bonds (e.g. octadecenoic acid for
18:1 (9 and octadecatrienoic acid for18:3( 9,12,15)
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Monounsaturated fatty acids contain 1C=C while polyunsaturated fatty acids
contain more than 1 C=C. Double bonds
are usual cis.
There is an alternative to the symbolic
representation of fatty acids, in which the
C's are numbered from the distal end (the
n or w end) of the acyl chain (the otherend from the carboxyl group)
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Hence 18:3( 9,12,15 could be written as 18:3
(w -3) or 18:3 (n -3) where the terminal C
is numbered one and the first double bond
starts at C3
Arachidonic acid is an (w -6) fatty acid
while docosahexaenoic acid is an (w -3)
fatty acid
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Symbol common
name
systematic
name
structure Mp
(C)
16:1( Palmitoleicacid
Hexadecenoicacid
CH3(CH2)5CH=CH-(CH2)7COOH
-0.5
18:1( Oleic acid 9-Octadecenoic
acid
CH3(CH2)7CH=CH-
(CH2)7COOH
13.4
18:2( Linoleic
acid
9,12 Octadeca-
dienoic acid
CH3(CH2)4(CH=CHCH2)2(
CH2)6COOH
-9
18:3( ELinolenic
acid
9,12,15 -
Octadecatrienoic
acid
CH3CH2(CH=CHCH2)3(CH
2)6COOH
-17
20:4(5,8,11,14 arachidonic
acid
5,8,11,14-
Eicosatetraenoic
acid
CH3(CH2)4(CH=CHCH2)4(
CH2)2COOH
-49
20:5(5,8,11,14,17 EPA 5,8,11,14,17-
Eicosapentaenoic
- acid
CH3CH2(CH=CHCH2)5(CH
2)2COOH
-54
22:6(4,7,10,13,16,19
DHA Docosohexaenoic
acid
22:6w3