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FATTY ACIDS
Fatty Acids ……… DEFINITION
• Fatty acid: a long, unbranched chain carboxylic
acid, most commonly of 12 - 20 carbons,
derived from hydrolysis of animal fats,
vegetable oils, or phosphodiacylglycerols of
biological membranes.
• Denovo synthesis occurs from acetyl coA
(lipogenesis)
• Fatty acids - are components of
triacylglycerols,
glycerophospholipids, sphingolipids
• Fatty acids differ from one another in:
(1) Length of the hydrocarbon tails
(2) Degree of unsaturation (double
bond)
(3) Position of the double bonds in the
chain
Prentice Hall c2002
Chapter 9
7
Fig 9.2
• Long Chain Fatty Acids are typically even numbered
• SATURATED no C-C double bonds
• UNSATURATED - at least one C-C double bond
• Monounsaturated - only one C-C double bond
• Polyunsaturated - two or more C-C double bonds
• Omega-3, omega-6 and omega-9
Fig. 9.3 Structures of three C18 fatty acids
(a) Stearate (octadecanoate)
(b) Oleate (cis-D9octadecenoate)
(c) Linolenate (all-cis-D9,12,15octadecatrienoate)
• The cis double bonds
produce kinks in the tails
of unsaturated fatty acids
Prentice Hall c2002
Chapter 9
10
Fatty Acids
Unsaturated
Saturated
Carbon Atoms/
Double Bonds
12:0
14:0
16:0
18:0
20:0
16:1
18:1
18:2
18:3
20:4
Common
Name
lauric acid
myristic acid
palmitic acid
stearic acid
arachidic acid
palmitoleic acid
oleic acid
linoleic acid
linolenic acid
arachidonic acid
mp
(°C)
44
58
63
71
77
-0.5
16
-5
-11
-49
Fatty Acids
• Among the fatty acids most abundant in plants and
animals
– nearly all have an even number of carbon atoms,
most between 12 and 20, in an unbranched chain
– the three most abundant are palmitic (16:0), stearic
acid (18:0), and oleic acid (18:1)
– in most 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
Difference between Cis & Trans
• If the acyl chains are
on the same side of the
bond, it is cis, example: oleic acid.
• if on opposite sides, it
is trans-, example:
elaidic acid, the
trans isomer of oleic
acid
• Double bonds in naturally occurring unsaturated
long-chain fatty acids are nearly all in the
cis configuration, the molecules being "bent"
120 degrees at the double bond. Thus, oleic acid
has an L shape, whereas elaidic acid remains
"straight.“
Clinical Significance
• Consumption of trans fatty acids  not good
for health.
• Previously in Margarine  Higher number of
Trans FA.
• Now soft margarine low in trans fatty acids or
containing none at all.
Hydrogenation Plant
• Hydrogenation involves:
– Heating oil
– Pressurizing oil
– hydrogen gas
– Using platinum catalyst
• Trans fats are a by
product of hydrogenation
• 0 g trans fats does not
mean zero
• It means <0.5 g per serving!
How Can Fatty Acids Modulate the Immune System?
• Why do we need immune modulation in
the first place?
• Answer: Similar to avoid excessive, chronic
inflammation which leads to tissue
destruction.
• FAs such as DHA and EPA can reduce
production of inflammatory cytokines (IL6, IL-12, IL-23)
• FAs can increase phagocytic activity
• FAs can decrease lymphocytic proliferation
• FAs can influence immune cell migration
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