This document discusses fatty acids. It defines fatty acids as long-chain organic acids with a carboxyl group and hydrocarbon tail. Fatty acids are classified based on length, saturation level, location of double bonds, and isomeric form. The document outlines essential fatty acids like omega-3 and omega-6 fatty acids and discusses the metabolism and functions of fatty acids. Trans fatty acids are formed during hydrogenation and may negatively impact cholesterol levels.

1. Fatty acids
1By: Zeravan Ali Sulaiman

2. Contents:
 Fatty acids definition.
 Functions of fatty acid.
 Nomenclature of fatty acids.
 Formation of fatty acid:
 Classification of fatty acids.
 Trans fatty acid.
 Essential fatty acids.
 Metabolism of fatty acids.
 References.
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3. Fatty acids definition:
 Fatty acids: Hydrolysis of triglycerides yield fatty acids. They
are long-chain organic acids having usually from 4 to 24
carbon atoms; they have a single carboxyl group and a long,
nonpolar hydrocarbon ‘tail’, which gives most lipids their
hydrophobic and oily or greasy nature.
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4. Structural formulas of some C18 fatty acids.
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5. Fatty acids:
 In higher plants and animals, the predominant fatty acid
residues are those of the C species palmitic, oleic, linoleic, and
stearic acids. Fatty acids with 14 or 20 carbon atoms are
uncommon. Most fatty acids have an even number of carbon 16
and C 18 fatty acids. The double bonds all have the cis
configuration atoms.
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6. Fatty acid:
 A fatty acid consists of a hydrophobic hydrocarbon chain with
a terminal carboxyl group that has a pKa of about 4.8 . At
physiologic pH, the terminal carboxyl group (–COOH) ionizes,
becoming –COO–. This anionic group has an affinity for water,
giving the fatty acid its amphipathic nature (having both a
hydrophilic and a hydrophobic region). However, for long-
chain fatty acids (LCFAs), the hydrophobic portion is
predominant. These molecules are highly water insoluble and
must be transported in the circulation in association with
protein.
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7. Formation of fatty acid:
 Triacylglycerol degradation: TAG molecules are too large to
be taken up efficiently by the mucosal cells of the intestinal
villi. They are, therefore, acted upon by an esterase, pancreatic
lipase, which preferentially removes the fatty acids at carbons 1
and 3. The primary products of hydrolysis are, thus, a mixture
of glycerol and three fatty acids
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8. Functions of fatty acid:
1. Fatty acids are source of energy for humans like glucose.
2. Fatty acids are components of nervous tissue, lipoproteins etc.
3. Poly unsaturated fatty acids are essential fatty acids.
4. They are required for the synthesis of eicosanoids.
5. They are also components of cell membrane
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9. Nomenclature of fatty acids:
 The most frequently used systematic nomenclature names the
fatty acid after the hydrocarbon with the same number and
arrangement of carbon atoms, with -oic being substituted for
the final -e (Genevan system).
 Thus, saturated acids end in -anoic, e.g., octanoic acid.
 Unsaturated acids with double bonds end in -enoic, e.g.,
octadecenoic acid (oleic acid).
 Carbon atoms are numbered from the carboxyl carbon (carbon
No. 1). The carbon atoms adjacent to the carboxyl carbon (Nos.
2, 3, and 4) are also known as the α, β, and γ carbons,
respectively, and the terminal methyl carbon is known as the ω
or n-carbon.
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10.  Various conventions use ∆ for indicating the number and
position of the double bonds (Figure 1); e.g., ∆9 indicates a
double bond between carbons 9 and 10 of the fatty acid; ω9
indicates a double bond on the ninth carbon counting from the
ω- carbon.
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Nomenclature of fatty acids:
Figure 1: Nomenclature of oleic acid.

11. Classification of fatty acids.
 Fatty acids are classified based on:
 Length of the carbon chain.
 Degree of saturation.
 Location of double bonds.
 Isomeric forms.
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12.  Fatty acids based on length of the carbon chain:
1. Short chain fatty acids: are fatty acids with aliphatic tails of 2-4
carbons (e.g. butyric acid C4:0).
2. Medium-chain fatty acids (MCFA): are fatty acids with aliphatic
tails of 6 to 10 carbons (Caprylic C8:0).
3. Long-chain fatty acids (LCFA): are fatty acids with aliphatic tails
of 12 or more carbons (Palmitic C16:0).
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Classification of fatty acids.

13.  Fatty acids based on Degree of saturation:
1. Saturated fatty acids:
 There are only single bonds between neighboring
carbons in the hydrocarbon chain.
 Molecules that fit closely together in a regular
pattern.
 Strong attractions between fatty acid chains.
 High melting points that make them solids at room temperature
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Classification of fatty acids.

14. Saturated fatty acids:
 More important are palmitic acid, stearic acid and
arachidonic acids.
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Symbol common name systematic name structure
12:0 Lauric acid dodecanoic acid CH3(CH2)10COOH
14:0 Myristic acid tetradecanoic acid CH3(CH2)12COOH
16:0 Palmitic acid Hexadecanoic acid CH3(CH2)14COOH
18:0 Stearic acid Octadecanoic acid CH3(CH2)16COOH
20:0 Arachidic acid Eicosanoic acid CH3(CH2)18COOH
Table 2: COMMON BIOLOGICAL SATURATED FATTYACIDS

15. 2. Unsaturated fatty acids:
 They contain double bonds in hydrocarbon chain.
 Most unsaturated fats are liquid at room
temperature and are called oils.
 Have “kinks” in the fatty acid chains.
 Do not pack closely.
 Have few attractions between chains.
 Typically contain cis double bonds.
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16. 16
Table 3: COMMON BIOLOGICAL UNSATURATED FATTY ACIDS
Symbol Common name systematic name Structure
18:1 Δ9 Oleic acid 9-Octadecenoic acid CH3(CH2)7CH=CH-(CH2)7COOH
18:2 Δ9,12 Linoleic acid
Omega 6
9,12 -Octadecadienoic
acid
CH3(CH2)4(CH=CHCH2)2(CH2)6COOH
18:3 Δ9,12,15 9,12,15 -Octadecatrienoic
acid
CH3CH2(CH=CHCH2)3(CH2)6COOH
 They are subdivided into mono unsaturated fatty acids and polyunsaturated
fatty acids (PUFA) based on number of double bonds.

17. Monounsaturated fatty acids:
 Have a single double bond.
 Liquid at room temperature.
 Example Oleic acid.
 Common sources: olive.
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18. Polyunsaturated fatty acids:

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19.  Fatty acids based on location of the double bonds:
Measured from the methyl end (CH3) (also called omega end ) to the
first double bond.
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Classification of fatty acids.

20.  Fatty acids based on Isomeric forms:
 "Trans" and "cis" refer to the direction of folding that occurs at the
carbon double bonds in unsaturated fatty acids.
 Cis fatty acids are the normal, natural directions for the folds. A
trans fatty acid is chemically identical to the cis form, but folds in
an unnatural direction. The trans fatty acids are created by heat (as
in deep frying) and by hydrogenation.
 The cis fatty acids have lower melting points than the trans fatty
acids or their saturated counterparts.
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Classification of fatty acids.

21. Cis and Trans fatty acids:
 The cis form has the two parts of the carbon chain bents toward each
other, and the trans has the two parts almost linear, similar to
saturated fatty acids.
 Linear molecules can pack together closely in a given space, and
give the substances a higher melting point, while bent molecules
cannot pack together easily, so that fats of these molecules have a
lower melting point.
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22. Trans fatty acid
 In hydrogenation process, double bonds of the cis- conformation in the
hydrocarbon chain may be converted to double bonds in the trans-
conformation.
 The nutritional properties of trans fatty acids have been debated for
many years, particularly with respect to their effects on the amounts of
low-density and high-density lipoprotein (LDL, HDL) contained in
human serum.
 Some studies have shown that trans fatty acids elevate the levels of
serum LDL cholesterol (bad cholesterol) and lower HDL cholesterol
(good cholesterol), a pattern that has been associated with poorer
cardiac outcomes.
 The increase in the ratio of total cholesterol to HDL cholesterol for
trans fatty acids was approximately double that for saturated fats.
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23. Essential Fatty acids:
 Essential fatty acids are not synthesized by the human body
fatty acid that must be of this is provided by the diet.
 There are two families of Essential Fatty Acids: omega-3 fatty
acids (n-3) and omega-6 (n-6).
 All essential fatty acids are polyunsaturated, so the 3 and the 6
mean that the first double bond is either 3 or 6 carbons in from the
end.
 Other fatty acids are sometimes classified as "conditionally
essential," meaning that they can become essential under some
developmental or disease conditions.
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24. Omega 3- Fatty Acids
 They are polyunsaturated fatty acids with first double bond three
carbon from methyl end.
 Source of omega-3 mostly in fish oils.
 There are three major types of omega-3 fatty acids from ingested
food and used by the body: alpha-Linolenic acid (ALA) and the
polyunsaturated fatty acids to long-chain Eicosapentanoic acid
(EPA) and Docosahexanoic acid (DHA).
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25.  They are polyunsaturated fatty acids with first double bond six
carbons from methyl end.
 Most of the omega-6 fatty acids are supplied by a diet based on
vegetable oils.
 Linoleic acid is converted in the body into polyunsaturated fatty
acids long chain, gamma-linolenic acid (GLA) and Arachidonic
acid (AA). The AA is also present directly into the meat and
GLA in vegetable oils.
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Omega 6- Fatty Acids

26. Essential roles of omega-3 and
omega-6:
1. Developing and maintaining good brain function.
2. The visual process.
3. Immune and inflammatory responses.
4. The production of molecules called “hormone-like”.
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27. Metabolism of Fatty Acids
 An adult consumes approximately 85 g of fat daily, most of it as
triacylglycerols. During digestion, free fatty acids (FFA) and
monoacylglycerols are released and absorbed in the small
intestine. In the intestinal mucosa cells, FFA are re-esterified to
triacylglycerols, which are transported via lymphatic vessels to
the circulation as part of chylomicrons. In the circulation, fatty
acids are transported bound to albumin or as part of lipoproteins.
 FFA are taken up into cells mainly by protein transporters in the
plasma membrane and are transported intracellularly via fatty
acid-binding proteins (FABP) (Figure 1).
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28. 28Figure 1: Metabolism of fatty acids.

29.  FFA are then activated (acyl-CoA) before they are shuttled via
acyl-CoA-binding protein (ACBP) to mitochondria or
peroxisomes for b-oxidation (and formation of energy as ATP
and heat) or to endoplasmic reticulum for esterification to
different classes of lipid. Acyl-CoA or certain FFA may bind to
transcription factors that regulate gene expression or may be
converted to signal molecules (eicosanoids). Glucose may be
transformed to fatty acids (lipogenesis) if there is a surplus of
glucose/energy in the cells. 29
Metabolism of Fatty Acids:

30.  Concentrations of fatty acids in blood (i.e., whole blood,
plasma, serum, and red blood cells) reflect both dietary intake
and biological processes (3). Humans can synthesize longer
omega-6 and omega-3 fatty acids from the essential fatty acids
linoleic acid (LA) and α-linolenic acid (ALA), respectively,
through a series of desaturation (addition of a double bond
between two carbon atoms) and elongation (addition of two
carbon atoms) reactions.
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Metabolism of Fatty Acids:

31. References:
 Rao, N., Biochemistry ; Questions and Answers2013.
 Murray, R.K., Granner, D.K., Mayes, P.A. and Rodwell, V.W., 2003. Overview
of Metabolism. Harper's Illustrated Biochemistry. 26th Ed. New York, Lange
Medical Books/McGraw-Hill, 125.
 Avissar, Y., et al., Biology: OpenStax. 2018.
 Dennis E. Vance & J.E. Vance. 1996. Biochemistry of Lipids, Lipoproteins and
Membranes. ELsevier.
 Ferrier, D., 2013. Biochemistry (Lippincott Illustrated Review). 6th ed.
Lippincott Williams & Wilkins.
 Rustan, A.C. and Drevon, C.A., 2001. Fatty acids: structures and properties. e
LS.
 Semma, M., Trans fatty acids: properties, benefits and risks. Journal of health
science, 2002. 48(1): p. 7-13.
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