unsaturated fattyacids.docx

Unsaturated fatty acids notes and study material

1. NAME: RADHIKA SUBODH TAWADIA
ROLL NUMBER: 48
FYBIOTECH

Unsaturated Fatty Acids

2. INTRODUCTION
Unsaturated fatty acids are fatty acids that contain one or more
double/triple carbon-carbon bonds in the carbon chain.
They are named by adding the suffix 'enoic' after the systematic
name.
They are similar to saturated fatty acids in the reaction of the
carboxylic group but also show properties due to presence of
the double bond.

On this basis this class of lipids can be divided into:
1) monounsaturated fatty acids (MUFAs), if only one double
bond is present; They are also referred as mono-enoic. In
most monounsaturated fatty acids the double bond is
between C-9 and C-10.
Palmitoleic (C=16) and oleic (C= 18) acids are present in
human body fat, as well as many vegetable oils. Erucic acid
(C=22) is a constituent of mustard oil and rapeseed oil.
Nervonic acid (C-24) is present in substantial quantities in
brain.

3. 2) polyunsaturated fatty acids (PUFAs), if at least two double
bonds are present; They are also referred as poly-enoic.
They are present in good quantities in vegetable oils such as
sunflower oil.
PUFA in general are anti-atherogenic (preventing or inhibiting
atherogenesis).
PUFA may be formed from monounsaturated fatty acids by the
introduction of double bonds only between an existing double
bond and carboxyl end of the fatty acid. Hence linoleic acid
cannot be synthesized from oleic acid. However, linoleic acid
can be converted to arachidonic acid by elongation and
desaturation.
Other PUFAS belonging to very long chain fatty acids (VLCFA)
are timnodonic acid (20 C, 5 double bonds); clupanodonic acid
(22 C, 5 double bonds) and cervonic acid (22 C, 6 double
bonds). They are present in fish oils. They are important for
development of human brain. They are nutritionally essential;
and are called Essential Fatty Acids.
Prostaglandins, thromboxane and leukotriene are produced
from arachidonic acid.
PUFAS form integral part of mitochondrial membranes. In
deficiency of PUFA, the efficiency of biological oxidation is
reduced.

The double bond in the molecule can generate two isomers
for unsaturated fatty acids:
cis and trans configurations.
The cis isomers have the two hydrogen atoms placed
adjacently to the double bond on the same side of the aliphatic

4. chain. The double bond gives rigidity to the molecule and the
cis conformation limits the conformational freedom of the fatty
acid. The more number of cis bonds found in a fatty acid, the
less flexible and curved it becomes in conformation. Example:
oleic and linoleic acid.
The trans isomers, conversely, have the two hydrogen atoms
placed on opposite sides of the aliphatic chain. The trans
configuration does not bend the structure of the molecule as
seen in cis isomers, but remains straight like saturated fatty
acids.
Most naturally occurring unsaturated fatty acids possess a cis
configuration whereas most trans fats are a result of human
processing, they do not occur naturally.
Examples of unsaturated fats: are myristoleic acid, palmitoleic
acid, sapienic acid, oleic acid, elaidic acid, vaccenic acid,
linoleic acid, linoelaidic acid, alpha-linolenic acid, arachidonic
acid, erucic acid, docosahexaenoic acid, and eicosapentaenoic
acid.

5. Properties of Unsaturated Fatty Acids
Acidity: Fatty acids have similar acidities. As the chain length of
a fatty acid increases, their solubility in water decreases, posing
no or little effect on the pH of the aqueous solution. Example:
Nonanoic acid (C9) has a pKa of 4.96 whereas acetic acid (C2)
has a pKa of 4.76.
Hydrogenation: Unsaturated fatty acids are prone to get rancid
(autoxidation or hydrolysis of fats when exposed to air).
Therefore the unsaturated fatty acids undergo hydrogenation to
minimise this problem. Unsaturated fatty acids are less stable
than saturated fatty acids. This makes them more vulnerable to
rancidity
Autoxidation: Unsaturated fatty acids undergo a chemical
change in the presence of air and trace metals called
autoxidation. Treatment with chelating agents can prevent this
action as they remove the metal catalysts.
Ozonolysis: Unsaturated fatty acids have high chances to get
degraded by ozone


 Nonlinear chains do not allow molecules to pack closely
 Weak attractions (dispersion force) between the fatty acid
chains
 Low melting points and so are liquid at room temperature
 Unsaturated fats have a shorter shelf life and can’t be
stored for a prolonged period without spoiling.
 Unsaturated fatty acids reduce LDL cholesterol levels in
the human body.

6.  Unsaturated fat acids constitute the oil component of the
lipids.
 30% of all calories required by the body come from
unsaturated fatty acids.