Name: _________________________________ Per:________ Performance: ________
BIOCHEMISTRY LAB # 7
LIPIDS
BACKGROUND
Lipids are a class of biological molecules that are grouped based on their similarities in
solubility. Lipids are not soluble in water. Lipids are soluble in nonpolar solvents such as ether,
chloroform, and benzene. Fatty acids, waxes, triglycerides, glycerophospholipids and steroids are
classes of compounds that are classified as lipids due to their similar solubility properties.
Lipids are a very diverse group of molecules that can be divided into five major subgroups
based on their structure and function in the body. Identify the lipid classes described below:
1. ________________________________: long chain hydrocarbons with a carboxyl
groups, parts of triglycerides and phospholipids
2. ________________________________: important mediators of immune response
3. ________________________________: food and body fats/oil
4. ________________________________: contain lipid hormones and cholesterols
5. ________________________________: main component of cell membranes
Cosmetics:
Lotions are mixtures of fats and water that have been hydrolyzed. The fat lubricates the top
layer of the skin, the water moves across the skin to hydrated deeper layers. In order to form a
homogeneous mixture of fats and water, an _________________________ has to be added, which are
_________________ molecules having hydrophillic parts that love water and lipophillic parts that love
fats.
Vitamins:
Several vitamins are fat soluble, i.e Vitamins A, D, E, K. Therefore, they can be better absorbed
if eaten with some fat that keeps them dissolved and facilitates the uptake. The picture below shows
Vitamin E. Circle and label the hydrophilic and hydrophobic parts of the Vitamin
Name: _________________________________ Per:________ Performance: ________
PROCEDURE
A. MODEL BUILDING: Triglycerides
Materials: Organic model kit
A.1. Build a model of glycerol and three molecules of ethanoic acid. What are the functional groups on
each? Draw their structure as you see it, use appropriate colors….
A.2. Form ester bonds between the hydroxyl groups on the glycerol and the carboxylic acid groups of
the ethanoic acid molecules. In the process, three molecules of water are removed. What is the
specific name of the product ________________________________.
Draw the reaction below in Kekule…..
The reverse Rx splitting Fats and Oils into their components is called _____________________, which
means you break each _______________ bond by inserting a molecule of water. Add an arrow to the
equation to show the reverse Rx.
B. PHYSICAL PROPERTIES OF SOME LIPIDS AND FATTY ACIDS
Materials: Micro-centrifuge tubes, dropper bottles or solids: stearic acid, oleic acid, olive oil, safflower
oil, lecithin, cholesterol, vitamin A, spatulas, methylene chloride

To seven separate micro-centrifuge tubes, add 5 drops or a small amount of solid lipid (3-4
granules) of the following substances:
a. stearic acid
e. lecithin
b. oleic acid
f. cholesterol
c. olive oil
g. vitamin A
d. safflower oil
B1: Describe their appearance in the table below
B2: Describe their smell in the table below
B3: Solubility in Polar Solvent:
 Add about 1.0 mL of water to each centrifuge tube. Cap the tubes and shake to mix. Record
your observations in the table below
B4. Solubility in a Nonpolar Solvent:
 Prepare 7 more fresh test tubes with a.-g. Add 0.5 mL methylene chloride CH2Cl2 to each
sample. Record the solubility of the lipids. Save the tubes and samples of stearic acid, oleic
acid, olive oil and safflower oil for part C.
Name: _________________________________ Per:________ Performance: ________
B. PHYSICAL PROPERTIES OF SOME LIPIDS AND FATTY ACIDS
Observations
Lipid
Stearic acid
Oleic acid
Olive oil
Safflower oil
Lecithin
Cholesterol
Vitamin A
B.1. Appearance
B.2. Odor
B.3. Soluble in
water?
B.4. Soluble in
CH2Cl2?
[Type text]
C. BROMINE TEST FOR UNSATURATION
The bromine test for unsaturation
The presence of unsaturation (the presence of double bonds) in fatty acids and triglycerides can
be detected using the bromine test. In this test you will add a bromine solution drop wise to the sample
and observe any color changes. The orange color of the bromine will fade rapidly with lipids that
contain unsaturations, until all the double bonds have reacted with the bromine. Lipids that have no
double bonds will immediately develop a orange color that does not fade.
Materials: Samples from B.4, 1% Br2 in methylene chloride.
 To the the samples saved from B4: stearic acid, oleic oil, olive oil and safflower oil in methylene
chloride, add 1% bromine solution drop by drop until a pale orange color is obtained or a max of
25 drops have been added.
Avoid contact with bromine solution; it can cause painful burns. Do not breathe the fumes!
Record your observations below. Determine if the red-orange color fades rapidly or persists.
C. BROMINE TEST FOR UNSATURATION
Lipid
Drops of
Bromine
added
Observations
Fatty acids
Stearic acid
Oleic acid
Triglycerides
Safflower oil
Olive oil
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[Type text]
D. PREPARATION OF HAND LOTION
Materials: Stearic acid, cetyl alcohol, lanolin (anhydrous), triethanolamine, glycerol, ethanol,
commercial hand lotions, 100 mL beakers, hot water bath, ice, crystallizing dish, 50 mL graduated
cylinder, spatula, beral pipette and stir rod.

Obtain the following substances and combine in two 50 mL beakers as indicated on the
following page. Use a laboratory balance/weigh paper to weigh out the solid substances, a
dropper bottle to measure small volumes and a graduated cylinder to measure larger volumes.
Beaker 1
Stearic acid
Cetyl alcohol
Lanolin (anhydrous)
Triethanolamine


1.5 g
0.5 g
1.0 g
10 drops
Beaker 2
4% Glycerin solution
25 mL
Place both beakers into a large water bath beaker (around 80°C) and heat for at least 2-3
minutes. Hold the edge of Beaker 1 and use a stir rod to mix the contents while melting.
Be careful that the beaker does not tip over inside the bath.
Remove the melted solids and heated glycerin solution, and while still warm, slowly pour the
glycerin solution from Beaker 2 into the warm melted solids inside Beaker 1 as you stir. Add
2.5 mL of ethanol and a few drops of fragrance. Continue to stir for 1-2 minutes until a smooth,
creamy lotion is obtained.
D1. Describe the smoothness and appearance of the hand lotion.
D.2. Compare your lotion with a commercially available one
D.3. Compare the properties of your hand lotion with one where triethanolamine has been omitted provided by teacher
D.4. Compare the properties of your hand lotion with one where stearic acid has been omitted provided by teacher
D.5. Determine the pH of the hand lotions from D1, D2, D3, and D4.
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PRE-LABORATORY QUESTIONS
1. Classify each of the compounds in part B of the procedure as a Fatty Acid, Triglyceride,
Phospholipid or Steroid.
2. For making the lotion you need Glycerin (glycerol), Stearic acid, Cetyl alcohol , Lanolin,
Triethanolamine. Draw the molecules in the space below, label them, circle/label the functional
groups they have and determine whether they are polar or non-polar What is the function of each
component in the lotion
3. Find a food label that contains lipids, cut it out and glue it in the space below. What food item is it?
List which of the following lipids (and how much) your food items has….
a.
b.
c.
d.
Saturated Fats ______
Trans Fats______
Polyunsaturated Fats _______
Monounsaturated Fats _________
4. A bromine (Br2) will react with the double bonds and break them open. This reaction type is
classified as _____________________ reactions, as it adds a new element to a molecule with a
double bond. Predict which of the substances below can react with Br2:
a.
b.
c.
d.
1-butene
butane
stearic acid
oleic acid (find the structure in the book)
5. Below, draw the reaction of oleic acid with Bromine gas. How many Br2 molecules do you need for
complete saturation of this fatty acid?
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D. PREPARATION OF HAND LOTION
Description of the hand lotions
D.1.
D.2. (without triethanolamine)
D.3. (without stearic acid)
D.4. pH of hand lotions
pH of commercial hand lotion
Brand _________________
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QUESTIONS
1. In part B you made some observations of the physical properties of several lipids. What property
(or properties) do all of the compounds have in common? Based on these common features why
do you think these compounds were classified as lipids?
2. In part C you performed the bromine test for unsaturation. Based on your observations what
compounds are unsaturated?
3. Based on your observations how can you use the bromine test to determine which compound is
more unsaturated?
4. Based on the acid and base properties of triethanolamine (weak base) and stearic acid (weak acid),
as well as your observations regarding the pH of lotions prepared with and without triethanolamine
and stearic acid, provide a reason as to why these two compounds are used as ingredients in hand
lotion.
5. Based your observations, in which lotion prepared is the water solubility of stearic acid improved?
With or without triethanolamine? Explain.
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