Download - Isolation cholesterol from egg yolk. Lipids Lipids are Biomolecules that contain fatty acids or a steroid nucleus. Soluble in organic solvents but.

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.


Types of Lipoproteins

Lipoproteins Differ in density, composition, and function. Include low-density lipoprotein (LDLs) and high-density

lipoprotein (HDLs).

TABLE 17.5


Transport of Lipoproteins in the Body


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