isolation cholesterol from egg yolk. lipids lipids are biomolecules that contain fatty acids or a...
TRANSCRIPT
Isolation cholesterol from egg yolk
Lipids
Lipids are Biomolecules that contain fatty acids or a steroid
nucleus. Soluble in organic solvents but not in water. Named for the Greek word lipos, which means “fat.” Extracted from cells using organic solvents.
Types of Lipids
Lipids with fatty acids
Waxes
Fats and oils (trigycerides)
Phospholipids
Sphingolipids
Lipids without fatty acids
Steroids
.
Structures of Lipids
Copyright © 2007 by Pearson Education, Inc.Publishing as Benjamin Cummings
Cholesterol
Cholesterol Is the most abundant steroid in the body. is a waxy substance found in all of the body
cells. Has methyl CH3- groups, alkyl chain, and -OH
attached to the steroid nucleus.
CH3
CH3CH3
CH3
HO
CH3
Function
help and maintain cell membranes. protect and insulate nerve fibers. involved in the formation of sex hormones, such as
estrogen. production of bile salts, which help digesting fats.
Cholesterol in the Body
Cholesterol in the body Is obtained from meats,
milk, and eggs. Is synthesized in the liver. Is needed for cell
membranes, brain and nerve tissue, steroid hormones, and Vitamin D.
Clogs arteries when high levels form plaque.
A normal, open artery.
Copyright © 2007 by Pearson Education, Inc.Publishing as Benjamin Cummings
An artery clogged by cholesterol plaque
Cholesterol in Foods
Cholesterol is Synthesized in
the liver. Obtained from
foods. Considered
elevated if plasma cholesterol exceeds 200 mg/dL.
TABLE 17.4
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
Lipoproteins
Lipoproteins• Combine lipids with proteins and phospholipids.• Are soluble in water because the surface consists of
polar lipids.
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
Types of Lipoproteins
Lipoproteins Differ in density, composition, and function. Include low-density lipoprotein (LDLs) and high-density
lipoprotein (HDLs).
TABLE 17.5
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
Transport of Lipoproteins in the Body
Copyright © 2007 by Pearson Education, Inc. Publishing as Benjamin Cummings
Low-density lipoprotein (LDL)
Low-density lipoproteins transport cholesterol
throughout the body, delivering cholesterol to different
tissues and organs. When the cells have all the
cholesterol they need, they reduce the number of
receptors, or gateways, for cholesterol to enter. As a
result, cholesterol contained in the LDL particles (LDL
cholesterol) starts to build up in the blood stream.
Over time, circulating LDL cholesterol undergoes
chemical changes (becomes oxidized) and also
reduces in size. These smaller particles more easily
enter the blood vessel wall and start to build up under
the vessel lining. Deposits of LDL cholesterol
particles in vessel walls are called plaques and can
lead to inflammation, bleeding into the area, and
calcium buildup (calcification). Eventually, the buildup
of plaques can start to crowd the space within the
blood vessel and obstruct the blood flow. This
process of plaque accumulation is called
atherosclerosis.
When atherosclerosis affects the arteries leading to
the heart (coronary arteries), one may have chest
pain and other symptoms of coronary artery disease.
If plaques tear or rupture, a blood clot may form —
blocking the flow of blood or breaking free and
plugging an artery downstream. If blood flow to part
of the heart stops, a heart attack will occur. If blood
flow to the brain stops, a stroke occurs. This is why
LDL cholesterol is often referred to as ―bad
cholesterol.
High-density lipoprotein (HDL)
Rather than deliver cholesterol to cells, high-density
lipoproteins leave the liver with very little cholesterol,
pick up excess cholesterol on their route through the
bloodstream and take it back to your liver. The liver
excretes this cholesterol into the bile and out of the
body through the bowels. Because HDL particles
remove excess cholesterol from the body, they are
considered protective. That’s why HDL cholesterol is
often referred to as ― good cholesterol.
Isolation of Cholesterol from egg yolk
Hen egg
Egg white
Albumin
Egg yolk
Lipids + glycoproteins
Egg yolk
Egg yolk
5% Cholestero
l
28% phospholip
ids
66% glycerides
Experiment
Reagents and instruments
A hard boiled hen egg Acetone, Ice, Water bath, Erlenmeyer flask, Funnel,
Filter paper, 250 ml beaker
Reagents and instruments
A hard boiled hen egg Acetone, Ice, Water bath, Erlenmeyer flask, Funnel, Filter paper, 250 ml beaker
1. Extraction
1. Peal the hard boiled egg and remove the egg white.
2. In a 250 ml beaker weigh a ½ egg yolk and mash it.
3. To the mashed egg yolk add a 25 ml of acetone and keep stirring for 5 min.
4. Allow the solid to settle and carefully remove the acetone (the above liquid phase) and transfer it to a clean 100 ml Erlenmeyer flask and cover it tightly.
5. To the remained solid phase add a new 25 ml of acetone and repeat step 4. Now you have collected twice the 25 ml of acetone extract (it contains the cholesterol).
2. Isolation
1. Using a funnel and a filter paper, filter the 50 ml of acetone extract into a clean 100 ml beaker.
2. Evaporate the acetone by placing the beaker on the steam bath in the hood until about 10 ml of extract is left.
3. Cover the warm acetone extract and immediately transfer it on ice and let it stand for 20 min. A white precipitate will form (this is the crude cholesterol). Remove the flask from ice. Get rid of the liquid phase.
4. To the cholesterol precipitate add 15 ml of acetone and stir at room temp.
Note that not all precipitate will dissolve (the contaminating phospholipids remain insoluble).
5. Weigh a clean, dry watch glass. Filter the dissolved cholesterol solution into the pre-weighed watch glass. Allow the acetone to evaporate in the hood. The remained crystals is the cholesterol.
6. Weigh the watch glass with cholesterol. Calculate the yield of cholesterol.
3 .Purification