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General Properties of Lipids
• Naturally-occurring organic compounds that
are:
1- insoluble in water
2- soluble in nonpolar organic solvents, such
as diethyl ether, acetone, carbon
tetrachloride.
3- Contain carbon, hydrogen, oxygen,
sometimes contain nitrogen and phosphorus
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4- Lipids can be extracted from cells and
tissues by organic solvents.
5- They yield fatty acids on hydrolysis or
combine with fatty acids to form esters.
6- The solubility property distinguishes lipids
from the three other major classes of natural
products —carbohydrates, proteins, and
nucleic acids—which in general are not
soluble in organic solvents.
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Lipids include..
1. Fats & Oils (Triglycerides)
2. Waxes: they are simple monoesters (acid &
alcohol).
3. Steroids
4. Fat-soluble vitamins (A, D, E, K)
5. Monoglycerides
6. Diglycerides
7. Phospholipids
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Fatty Acids
1. Straight-chain organic acids
2. Found in natural fats, usually contain an even
number of carbon atoms.
3. Can be either saturated or unsaturated
4. Polyunsaturated fatty acids contain many double
bonds.
5. Unsaturated fatty acids have a lower melting
point than the corresponding saturated fatty
acids.
6. The greater the degree of unsaturation, the
lower the melting point.
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Some Common Fatty acids
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Fatty Acid Composition of Some Fats and Oils
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Classification of Lipids
• Lipids can be classified into three classes:
1. Simple lipids
2. Complex lipids
3. Precursor & Derived lipids
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1. Simple Lipids
• They are esters of fatty acids, upon hydrolysis
they give fatty acids & alcohol:
simple lipid
hydrolysis
Fatty acids + Alcohol
• If the result of hydrolysis is:
1. three fatty acids & glycerol (then it is fat or oil)
2. One fatty acid and high molecular mass
monohydric alcohol (then it is wax such as
carnauba, bees wax)
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2. Complex Lipids
• Are lipids that give one or more fatty acids, an
alcohol, and some other type of compounds.
Complex lipids
hydrolysis
fatty acid + alcohol + other compounds
• Some examples of complex lipids:
1. Phospholipids
2. Glycolipids (cerebrosides)
3. Sulfolipids
4. Aminolipids
5. Lipoproteins
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for example will give fatty acids,
alcohol, phosphoric acid, and a nitrogenous
compound upon hydrolysis
• They are subdivided into 2 groups:
- Phosphoglycerides (alcohol is glycerol)
- Phosphosphingosides (alcohol is sphingosine which
is a nitrogen-containing alcohol)
sphingosine
(glycosphingolipids) give fatty
acids,carbohydrate, and a sphingosine upon
hydrolysis.
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3. Precursor & Derived Lipids
are compounds produced from
the hydrolysis of simple & complex lipids (fatty
acids, glycerol, sphingosine).
are formed during the metabolic
transformation of fatty acids in the human body
such as:
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Fats & Oils
• Fats are esters of a fatty acid with one
particular alcohol, glycerol.
• Examples:
• 1 molecule of glycerol will reacts with 1
molecule of stearic acid and gives
• C17H35COOH
+
+ + H2O
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• Reacting with a second molecule of stearic
acid, glycerol will give
• While reacting with a third molecule of stearic
acid, glycerol will give
(also known as
).
• Note: Fats & oils can contain same three fatty acids
or different ones which can be saturated,
unsaturated or some combination of these.
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Iodine Number
• The number of grams of iodine that will react with
double bonds present in a 100 g of fat or oil.
• Unsaturated fats & oils will react with iodine, while
saturated fats & oils will not react with iodine readily.
• The more unsaturated the fat or oil is, the more iodine
it will combine
• Conclusion:
have a lower iodine number (more
saturated)
have a higher iodine number (more
unsaturated).
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• Fats have iodine number below 70, while oils
have iodine number above 70.
oils should not be
confused with mineral oils, which is a mixture
of saturated hydrocarbons.
: are volatile aromatic liquids
used as flavors and perfumes.
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Used of Fats in the body
, producing more
energy/g than either carbohydrate or protein
produce.,
are produced from protein or carbohydrate
are produced by fats.
in storing energy in the body
than carbohydrate.
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for the organs (by
surrounding them for stabilizing).
helping to
keep body warm in cold weather.
which are
found in cell membranes, and in
mitochondria.
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Physical Properties of Fats & Oils
• Pure fats are white, solid
• Pure oils are yellow, liquid.
• Odorless & tasteless, but over a period of time
they become rancid.
• Insoluble in water
• Soluble in organic solvents such as benzene,
acetone, ether.
• Fats do not diffuse through a membrane.
• Fats have a greasy feeling.
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• Fats form a
when shaken
with water.
- The emulsion can be made permanent by the
addition of an
such as soap.
- Fats & oils must be emulsified by the bile
before they can be digested.
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Chemical Properties of Fats & Oils
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is made by hydrogenating cottonseed,
soybean, peanut, or corn oil until the desired
butter-like consistency is obtained.
The product may be churned with milk and
artificially colored to mimic butter’s flavor and
appearance.
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Hydrolysis:
 When butter is let to stand at room temp.
hydrolysis takes place between the fats and
the water present in the butter.
The result of this hydrolysis is fatty acid and
glycerol.
One of the products of the hydrolysis is
butyric acid, responsible for the disagreeable
odor.
Note: to avoid rancidity keep the butter
covered in a cool place.
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Oxidation:
 Oxygen present in air oxidizes some
unsaturated fatty acids of fats & oils.
If this oxidation produces a short chain acids
or aldehydes, the fat turns rancid (as
evidenced by a disagreeable odor and taste).
Oxidation of fats can be inhibited by the
addition of antioxidants such as vitamin C & E.
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How do Soaps work?
• Soaps are salts of fatty acids, produced by
reacting of fats with strong bases.
• 2 Types of soaps:
- Bar soap: NaOH is the base (solid soap)
- Soft soap: KOH is the base (liquid soap)
F. A + NaOH
Sodium salt of F.A + H2O
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Prostaglandins, Leukotrienes, and Lipoxins
• Prostaglandins are a group of compounds related to
the unsaturated fatty acids.
• On the assumption that these substances came from
the prostate gland, they were named prostaglandins.
• We now know that prostaglandins are widely
• distributed in almost all human tissues, that they are
biologically active in minute concentration, and that
they have various effects on:
- fat metabolism,
- heart rate,
- blood pressure.
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• Prostaglandins have excited much interest in the
medical community, where they are used in the
treatment of:
- inflammatory diseases, such as asthma and
rheumatoid arthritis;
- treatment of peptic ulcers;
- control of hypertension;
- regulation of blood pressure
- metabolism;
- inducing of labor
- therapeutic abortions.
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Steroids
• Tetracyclic compounds with high molecular
mass.
• Steroids containing 1 or more OH groups are
called sterols.
• Most common sterol is cholesterol, found in
animal fat.
• Most of body cholesterol is produced by liver
• Bile salts, sex hormones (testosterone &
estrogen) are synthesized from cholesterol.
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Anabolic Steroids
• Hormones that control the synthesis of larger
molecules from smaller ones.
• Example of anabolic steroids:
1. Testosterone: it increases muscle mass
 Side effects of anabolic hormones
•
In men
- Testicular atrophy
- hypercholesterolemia
- Breast growth
- Liver cancer
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• In women
- Increased masculinity
- Formation of a greater body hair
- Deepening of the voice
- menstrual irregularities
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