5. DERIVED LIPIDS
FATTY ACIDS
Definition:
A fatty acid (FA) may be defined as an organic acid
that occurs in a natural triglyceride and is a mono-
carboxylic acid ranging in chain length from C4 to
about 24 carbon atoms. FA are obtained from
hydrolysis of fats.
6. (a) Fatty acids may be
•Saturated
•Unsaturated
•cyclic
(b) Monoglycerides (Monoacylglycerol) and Diglycerides (Di-
acylglycerol
(c) Alcohols:
1. Straight chain alcohols
2. Cholesterol and other steroids including Vit D
3. Alcohol containing β-ionone ring include Vit A and certain
carotenoids
4. Glycerol
7. FATTY ACIDS
Fatty acids are important component of lipids.
• Generally, a fatty acid consists of a straight chain of an
even number of carbon atoms, with hydrogen atoms
along the length of the chain and at one end of the
chain and a carboxyl group (―COOH) at the other
end.
• It is that carboxyl group that makes it an acid
(carboxylic acid).
• If the carbon-to-carbon bonds are all single, the acid is
saturated.
• If any of the bonds is double or triple, the acid is
unsaturated and is more reactive.
10. FATTY ACIDS
• A few fatty acids have branched chains; others contain
ring structures (e.g., prostaglandins).
• Fatty acids are not found in a free state in nature;
commonly they exist in combination with glycerol (an
alcohol) in the form of triglyceride.
• The most widely distributed fatty acids are the 16- and
18-carbon fatty acids, palmitic acid and stearic acid.
• Palmitic acid makes up 30 percent of body fat.
• 5 to 50 percent of lipids in vegetable fats( palm oil).
• Stearic acid is abundant in some vegetable oils
e.g., cocoa butter
11. Nomenclature of Fatty acids
Carbon atom numbering
• The position of the carbon atoms in the backbone of a fatty acid are
usually indicated by counting from 1 at the −COOH end.
• By Greek alphabet in sequence, starting with the first
carbon after the carboxyl. Thus carbon α (alpha) is C-2, carbon β
(beta) is C-3, and so forth.
• The last carbon in the chain is always labelled as ω (omega), which is
the last letter in the Greek alphabet. A third numbering convention
counts the carbons from that end, using the labels "ω", "ω−1",
"ω−2", where the "n" is meant to represent the number of carbons
in the chain.
12. Nomenclature of Fatty acids
Carbon atom numbering
• The position of a double bond in a fatty acid chain is always specified
by the carbon closest to the carboxyl end.
• Thus, in an 18 carbon fatty acid, a double bond between C-12 (or
ω−6) and C-13 (or ω−5) is at position C-12 or ω−6. The naming of the
fatty acid based on the "C" numbering.
• The notation Δx,y,... is specify a fatty acid with double bonds at
positions x,y,.... Thus, for example, the 18-carbon fatty acid is
Δ6,9,12,15, meaning that it has double bonds between carbons 6 and 7,
9 and 10, 12 and 13, and 15 and 16.
• Arachidonic acid (18:4; 6,9,12,15):
13. FATTY ACIDS
Fatty acids have a wide range of commercial
applications. For example,
• they are used in the production numerous food
products.
• Also in soaps, detergents, and cosmetics.
• Fatty acids, particularly omega-3 fatty acids, are
also commonly sold as dietary supplements.
14. TYPES OF FATTY ACIDS
Fatty acids are classified in many ways:
• By length of carbon chain,
• By saturation vs unsaturation,
• By even vs odd carbon content,
• By linear vs branched
15. TYPES OF FATTY ACIDS
Length of fatty acids
• Short-chain fatty acids(SCFA) are fatty acids with aliphatic
tails of five or fewer carbons e.g. butyric acid.
• Medium-chain fatty acids (MCFA) are fatty acids
with aliphatic tails of 6 to 12 carbons, which can
form medium-chain triglycerides.
• Long-chain fatty acids (LCFA) are fatty acids with aliphatic tails
of 13 to 21 carbons.
• Very long chain fatty acids (VLCFA) are fatty acids
with aliphatic tails of 22 or more carbons.
17. a. Saturated Fatty Acids
Saturated fatty acids have no C=C double bonds.
Their general formula is CnH2n+1COOH.
Examples:
Acetic acid CH3COOH
Propionic acid C2H5COOH
Butyric acid C3H7COOH
Caproic acid C5H11COOH
Palmitic acid C15H31COOH
Stearic acid C17H35COOH and so on.
18. Saturated Fatty Acids
• Saturated fatty acids having 10 carbon or less
number of carbon atoms are called as “Lower fatty
acids”, e.g. acetic acid, butyric acid, etc. Milk
contains significant amount of lower fatty acids.
• Saturated fatty acids having more than 10 carbon
atoms are called “higher fatty acids”, e.g. palmitic
acid, stearic acid, etc.
19. b) Unsaturated FA
They are classified further according to degree of
unsaturation(no of double bonds).
(1) Mono unsaturated fatty acids: are those which
contain one double bond.
•Example: Oleic acid C17H33 COOH is found in nearly
all fats (formula 18:1;9).
20. b) Unsaturated FA
Polyunsaturated fatty acids:
fatty acids have more than one C=C double bonds.
•Linoleic acid series (18 : 2; 9, 12): It contains two
double bonds between C9 and C10; and between C12
and C13.
•Dietary sources:
•Linoleic acid is present in sufficient amounts in peanut
oil, corn oil, cottonseed oil, soybean .oil and egg yolk.
21. b) Unsaturated FA
Polyunsaturated fatty acids:
fatty acids have more than one C=C double bonds.
Linolenic acid (18:3; 9,12,15): It contains three
double bonds between 9 and 10; 12 and 13; and 15
and 16.Found frequently in linseed oil, soybean oil,
fish liver oil (cod liver oil).
22. b) Unsaturated FA
Polyunsaturated fatty acids:
•Arachidonic acid ;it contains 4double bonds.
•Dietary Source:
•Found in small quantity with linoleic and linolenic
acid but found particularly in peanut oil, also found
in animal fats including liver fats.
23. b) Unsaturated FA
The C=C double bonds can give either cis or trans isomers.
• cis configuration :
• means that the two hydrogen atoms adjacent to the double
bond stick out on the same side of the chain, causes the
chain to bend. When a chain has many cis bonds, it becomes
quite curved in its most accessible conformations.
• For example, oleic acid, with one double bond, has a "kink"
in it,
• whereas linoleic acid, with two double bonds, has a more
pronounced bend.
• α-Linolenic acid, with three double bonds, favours a hooked
shape.
24. b) Unsaturated FA
Trans unsaturated fatty acids
• means that the adjacent two hydrogen atoms lie
on opposite sides of the chain. As a result, they do
not cause the chain to bend much, and their shape
is similar to straight saturated fatty acids.
• Some trans fatty acids also occur naturally in the
milk and meat. Also in breast milk of women who
obtained them from their diet.
25. Note:
These three poly unsaturated fatty acids viz. linoleic
acid, linolenic acid and arachidonic acid are called as
"Essential fatty acids (EFA). They have to be provided
in the diet, as they cannot be synthesized in the
body.
26. ESSENTIAL FATTY ACIDS
Three polyunsaturated fatty acids, Linoleic acid,
Linolenic acid and Arachidonic acid are called
“essential fatty acids” (EFA). They cannot be
synthesized in the body and must be provided in
the diet. Lack of EFA in the diet can produce
growth retardation and other deficiency
manifestation symptoms.
27. Linoleic acid is most important as, arachidonic acid
can be synthesized from Linoleic acid by a three
stage reaction by addition of Acetyl-C0A. Pyridoxal
phosphate is necessary for this conversion.
Biologically arachidonic acid is very important as it
is precursor from which prostaglandins and
leukotrienes are synthesized in the body.
28. Functions of EFA: (Biomedical Importance)
• Structural elements of tissues:
Polyunsaturated fatty acids occur in higher
concentration in lipids associated with structural
elements of tissues.
• Structural element of gonads:
Lipids of gonads also contain a high concentration of
polyunsaturated fatty acids, which suggests
importance of these compounds in reproductive
function.
29. Functions of EFA: (Biomedical Importance)
• Synthesis of prostaglandins and other
compounds:
Prostaglandins are synthesized from Arachidonic acid.
• Structural element of mitochondrial membrane:
A deficiency of EFA causes swelling of mitochondrial
membrane and reduction in efficiency of oxidative
phosphorylation. This leads to increased heat
production noted in EFA deficient animals.
30. Functions of EFA: (Biomedical Importance)
• Serum level of cholesterol:
Fats with high content of polyunsaturated fatty acids
tends to lower serum level of cholesterol.
• Effect on clotting time:
Prolongation of clotting time is noted in ingestion of fats
rich in EFA.
• Effect on fibrinolytic activity:
An increase in fibrinolytic activity follows the ingestion of
fats rich in EFA.
31. Functions of EFA: (Biomedical Importance)
• Role of EFA in fatty liver:
Deficiency of EFA produces fatty liver.
• Role in Vision:
Docosahexenoic acid is the most abundant polyeneoic
fatty acids present in retinal photoreceptor
membrances. Docosahexenoic acid is formed from
dietary linolenic acid. It enhances the electrical
response of the photoreceptors to illumination.
Hence linolenic acid is necessary in the diet for
optimal vision.
32. DEFICIENCY MANIFESTATIONS
A deficiency of EFA has not yet been demonstrated in
humans. In weaning animals, symptoms of EFA
deficiency are readily produced. They are:
– Cessation of growth.
– Skin lesions:
– Abnormalities of pregnancy and lactation in adult
females.
– Fatty liver accompanied by increased rates of fatty acids
synthesis.
– Kidney damage.
33. CLINICAL ASPECT
Human Deficiency:
• Eczema like dermatitis,
• Degenerative changes in arterial wall and
• Fatty liver in man may be due to E.F.A..
deficiency.
34. There are also some reports that administration of
EFA in such cases may produce:
Some improvement of eczema in children kept on
skimmed milk,
Prevent fatty liver (some cases) and
Lowering of cholesterol levels.
Infants and babies with low fat diet develop typical skin
lesions which has shown to be improved with EFA
(linoleic acid).
35. TYPES OF FATTY ACIDS
By linear vs branched:
• Branched Chain FA; Odd and even carbon branched
chain fatty acids occur in animal and plant lipids,
e.g.
• Sebaceous glands: Sebum contain branched chain
FA
• Branched chain FA is present in certain foods, e.g.,
butter.
36. TYPES OF FATTY ACIDS
Even vs odd carbon content:
• Most fatty acids are even-chained (ECFA)., e.g. stearic
(C18) and oleic (C18), meaning they are composed of
an even number of carbon atoms.
• Some fatty acids have odd numbers of carbon atoms;
they are referred to as odd-chained fatty acids (OCFA).
The most common OCFA are the saturated C15 and
C17 derivatives, which are found in dairy products.
• On a molecular level, OCFAs are biosynthesized and
metabolized slightly differently from the even-chained
relatives
37. TYPES OF FATTY ACIDS
Cyclic Fatty Acids: Fatty acids bearing cyclic groups
are present in some seeds, e.g.Hydnocarpic acid.
• used earlier for long time for treatment of Leprosy.
38. TYPES OF FATTY ACIDS
Eicosanoids:
• These are derived from eicosapolyenoic FA.
Eicosanoids are signaling molecules made by
oxidation of twenty-carbon essential fatty acids,
(EFAs). They exert complex control over many
systems, mainly in inflammation or immunity, and as
messengers in the central nervous system. The
networks of controls that depend upon eicosanoids
are among the most complex in the human body.
