Lipids and Their Biological Role
Lipids-I
-
Lipids
are
esters of long chain fatty acids and alcohols
.
-Fatty acids are lipids’ building blocks
-It can be defined as
nonpolar
organic compound insoluble in polar solvent , but
soluble in organic solvents
such as benzene ,ether, chloroform and boiling alcohol.
Biological role of lipids:
Lipids are found naturally in all living organisms.
1)It represents in cell structure and has a structural function in the cell : it presents in cell membranes.
2) An essential source of energy in the body. It give more energy than carbohydrate and proteins.
Fats can be divided according to their chemical composition to:
1) Simple lipids:
-
These compounds are: esters of fatty acids with glycerol.
-The triacylglycerol (TAG) is the simplest and most common fat.
It is the form in which lipids are stored in the cell.
2) Compound (conjugated) lipids.
Lipids are linking with other compounds such as Proteolipids,
Phospholipids, Glycolipids
3) Derived lipids.
They are substances that are soluble in lipid or derived from the above groups
of lipids by hydrolysis; for examples, cholesterol and fat soluble vitamins.
1-Solubility test:
Objective:
to test the solubility of oils in different solvent.
Principle:
Fats are not dissolved in water due to their nature, which is
non-polar
(hydrophobic), but it is
soluble in organic
solvents
such as chloroform, benzene, and boiling alcohol.
Note:
Different lipids have ability to dissolve in different organic solvent. This property enable us to separate a
mixture of fat from each other.
Method
:
Place 0.5ml of oil in 6 test tubes clean, dry containing 4ml of different solvents (
acetone, chloroform , ether and
ethanol, diluted acid and dilute alkaline
),
Shake the tubes thoroughly, then leave the solution for about one minute,
Note:
if it separated into two layers , the oil are not dissolve; but if one layer homogeneous transparent formed
, oil be dissolved in the solvent
Results:
2-Saponification test:
Objective
:
to form the soap.
TAG can be
hydrolyzed
into its component fatty acids and alcohol. This reaction can also be carried out in the
laboratory by a process called saponification where the hydrolysis is carried out
in the presence of a strong base
(such as NaOH or KOH).
Principle:
Saponification is a process of
hydrolysis of oils or fat with alkaline
and result in
glycerol
and
salts of fatty acids
(soap) .
Note:
soap is salt of fatty acid.
The soap is
soluble in water
but insoluble in ether. Soap
works on emulsification
of oils and fats in the water .
Method:
•Place 2 ml of oil in a large test tube (or flask).
• Add 4 ml of alcoholic potassium hydroxide.
• Boil the solution for 3 minutes. After this period, make sure it is perfectly saponification process, by taking a
drop of the solution and mix with the water if oil separated indicates that the non-completion of the
saponification. In this case, continued to boil until all the alcohol evaporates.
• Take the remaining solid material (soap) and add about 30 ml of water and keep it for the following tests.
• Shake the solution after it cools and noted to be thick foam.
3- Testing the separation of soap from the solution by salting out :
Objective:
to investigate the effect of NaCl on soap solubility.
Principle:
To get the soap out of solution by
salting out
, when added solid sodium chloride to the solution until saturation;
separated soap in the form of insoluble and floats above the surface.
The NaCl solution provides Na
+
and Cl
-
ions that bind to the polar water molecules, and help separate the water
from the soap. This process is called salting out the soap.
Method:
Place about 10 ml of soap in the beaker, then add small amounts of sodium chloride in batches, stirring until
saturated solution.
4-Test formation insoluble fatty acids salt (insoluble soaps):
Objective:
to investigate the effect of different cations on soap solubility.
Principle:
-Working calcium, magnesium, lead or iron ions to the
deposition
of soap and
make it insoluble in water
, where
solve these
ions replace the sodium or potassium ions are present in soap
.
-Due to the
hard water
contain significant quantities of Ca2+ , Mg2+ and some Fe3+ that react with the charged
ends of the soaps to form insoluble salts of fatty acid. The insoluble salts of fatty acid that Ca
2+
and Mg
2+
form with
soap anions cause
white precipitate to from
.
(a
white precipitate
from calcium stearte or oleate is formed).
Note:
hard water, which contains salts of magnesium and calcium
K+ soap + Ca+2sulfate => Ca+2 soap + K+ sulfate.
Potassium soap + calcium sulfate => calcium soap + potassium sulfate.
Method:
1 - Add about 4 ml of distilled water to 2 ml of soap in two test tubes.
2 - Add to the first tube a few drops of calcium chloride, to second tube MgCl.
Result:
Questions :
What is the chemical composition of soap?
How does soap emulsify oil?
What happens to the soap when washing with hard water ?
Lipids are esters of long-chain fatty acids and alcohols, playing essential roles in cell structure, energy storage, and more. Learn about the different types of lipids, their solubility tests, and the process of saponification in this informative guide.
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Presentation Transcript
Lipids-I http://healthdirectusa.com/images/uploads/2012082316413937365_big.jpg
-Lipids Lipids are esters of long chain fatty acids and alcohols. -Fatty acids are lipids building blocks -It can be defined as nonpolar such as benzene ,ether, chloroform and boiling alcohol. nonpolar organic compound insoluble in polar solvent , but soluble in organic solvents Biological role of lipids: Biological role of lipids: Lipids are found naturally in all living organisms. 1)It represents in cell structure and has a structural function in the cell : it presents in cell membranes. 2) An essential source of energy in the body. It give more energy than carbohydrate and proteins.
Fats can be divided according to their chemical composition to: 1) Simple lipids: -These compounds are: esters of fatty acids with glycerol. -The triacylglycerol (TAG) is the simplest and most common fat. It is the form in which lipids are stored in the cell. 2) Compound (conjugated) lipids. Lipids are linking with other compounds such as Proteolipids, Phospholipids, Glycolipids https://figures.boundless.com/19976/large/0302-phospholipid-bilayer.jpe 3) Derived lipids. They are substances that are soluble in lipid or derived from the above groups of lipids by hydrolysis; for examples, cholesterol and fat soluble vitamins.
1 1- -Solubility test: Solubility test: Objective: Objective: to test the solubility of oils in different solvent. Principle: Principle: Fats are not dissolved in water due to their nature, which is non solvents such as chloroform, benzene, and boiling alcohol. non- -polar polar (hydrophobic), but it is soluble in organic Note: Different lipids have ability to dissolve in different organic solvent. This property enable us to separate a mixture of fat from each other.
Method Method: Place 0.5ml of oil in 6 test tubes clean, dry containing 4ml of different solvents (acetone, chloroform , ether and ethanol, diluted acid and dilute alkaline ethanol, diluted acid and dilute alkaline), Shake the tubes thoroughly, then leave the solution for about one minute, acetone, chloroform , ether and Note: Note: if it separated into two layers , the oil are not dissolve; but if one layer homogeneous transparent formed , oil be dissolved in the solvent Results: Results: Tube Solvent Degree of solubility
2 2- -Saponification test: Saponification test: Objective Objective: to form the soap. TAG can be hydrolyzed laboratory by a process called saponification where the hydrolysis is carried out in the presence of a strong base (such as NaOH or KOH). hydrolyzed into its component fatty acids and alcohol. This reaction can also be carried out in the in the presence of a strong base Principle: Principle: Saponification is a process of hydrolysis of oils or fat with alkaline hydrolysis of oils or fat with alkaline and result in glycerol and salts of fatty acids (soap) . Note: Note: soap is salt of fatty acid. soap is salt of fatty acid. The soap is soluble in water of oils and fats in the water . soluble in water but insoluble in ether. Soap works on emulsification
Method: Method: Place 2 ml of oil in a large test tube (or flask). Add 4 ml of alcoholic potassium hydroxide. Boil the solution for 3 minutes. After this period, make sure it is perfectly saponification process, by taking a drop of the solution and mix with the water if oil separated indicates that the non-completion of the saponification. In this case, continued to boil until all the alcohol evaporates. Take the remaining solid material (soap) and add about 30 ml of water and keep it for the following tests. Shake the solution after it cools and noted to be thick foam.
3 3- - Testing the separation of soap from the solution by salting out : Testing the separation of soap from the solution by salting out : Objective: Objective: to investigate the effect of NaCl on soap solubility. Principle: Principle: To get the soap out of solution by salting out separated soap in the form of insoluble and floats above the surface. salting out, when added solid sodium chloride to the solution until saturation; The NaCl solution provides Na+ and Cl- ions that bind to the polar water molecules, and help separate the water from the soap. This process is called salting out the soap.
Method: Method: Place about 10 ml of soap in the beaker, then add small amounts of sodium chloride in batches, stirring until saturated solution.
4 4- -Test formation insoluble fatty acids salt (insoluble soaps): Test formation insoluble fatty acids salt (insoluble soaps): Objective: Objective: to investigate the effect of different cations on soap solubility. Principle: Principle: -Working calcium, magnesium, lead or iron ions to the deposition solve these ions replace the sodium or potassium ions are present in soap. deposition of soap and make it insoluble in water make it insoluble in water, where -Due to the hard water ends of the soaps to form insoluble salts of fatty acid. The insoluble salts of fatty acid that Ca2+ and Mg2+ form with soap anions cause white precipitate to from white precipitate to from. hard water contain significant quantities of Ca2+ , Mg2+ and some Fe3+ that react with the charged
K+ soap + Ca+ K+ soap + Ca+2 2sulfate => Ca+ sulfate => Ca+2 2 soap + K+ sulfate. soap + K+ sulfate. Potassium soap + calcium sulfate => calcium soap + potassium sulfate. Potassium soap + calcium sulfate => calcium soap + potassium sulfate. (a white precipitate white precipitate from calcium stearte or oleate is formed). Note: Note: hard water, which contains salts of magnesium and calcium
Method: Method: 1 - Add about 4 ml of distilled water to 2 ml of soap in two test tubes. 2 - Add to the first tube a few drops of calcium chloride, to second tube MgCl. Result: Result: Tube Observation Conclusion CaCl2 MgCl2
Questions : Questions : What is the chemical composition of soap? How does soap emulsify oil? What happens to the soap when washing with hard water ?
