Chem 152: Biochemistry laboratory
Department of Chemistry
School of Science and Engineering
Loyola Schools, Ateneo de Manila University
Lipids
Gloves are not needed for this experiment. Please make sure you bring the assigned samples below.
Introduction
Lipids are water-insolule organic biomolecules that can be extracted from cells and tissues but rarely are they
present in a “free” or “uncombined” state. Lipids are involved in a whole array of biological functions,
including membrane structural integrity, vitamin activity, cell recognition, and cellular energy. The major
classes of compounds represented in the lipid group are triacylgycerols, glycerophosphatides, sphingolipids,
glycolipids, and sterols.
General Notes
• Everything must be kept dry. Dry your glassware in the oven or by washing with ethanol then acetone
Prelab
- No reagent list needed.
Data Sheet
 On your lab notebook, create a table containing the substances tested, tests conducted and the tests
results.
 Explain briefly (one paragraph) why the results are observed.
To be tested
• Bring your own samples (by pair) – at least 3 samples (please coordinate with the class so that samples will
not repeat). Possible samples: used cooking oil, canola oil, sesame oil, peanut oil, soybean oil, different
types of wax, baby oil, coconut oil, olive oil, corn oil, lard, margarine, butter, etc.
• As a class, bring small amounts of the following (Gian, please take charge of buying and the class will just
pay or assign the items to those who have these in there kitchens.) (about 50mL is fine): all purpose cream,
full cream milk, skim milk.
Procedure
A. Solubility
1. Note the physical properties and state of the different fats and oils.
2. Test their solubilities (5 drops of oil or similar amount) in
a. Water
b. Chloroform
c. Ethanol
d. Soapy Water
B. Test for unsaturation
Halogens add to double bonds.
1. Add 1 drop of oil or one spatula tip of solid fat into a test tube to test it. Dissolve in 1 mL of
chloroform or ethanol (see result above).
2. Add 1 mL of chloroform as blank to another tube.
3. Add dropwise a solution in bromine in chloroform until a yellow color is produced. Note the number
of drops.
C. Acrolein test
When fat is decomposed using a strongly dehydrating agent, glycerol is dehydrated forming
CH2=CHCHO (acrolein), which has a characteristic unpleasant odor. This is a standard test for
triglycerides.
1. Control:
a. Add about 3 spatula points of anhydrous potassium hydrogen sulfate to a test tube and add one
drop of glycerol.
b. Heat the tube strongly and CAREFULLY note the odor of the fumes evolved.
2. Sample
a. Place 1 g of anhydrous potassium hydrogen sulfate and add 5 drops of oil or a little bit of solid fat
in a test tube.
b. Heat for a few minutes and note the odor.
D. Peroxide test
Peroxides tend to form when double bonds are oxidized.
1. Dissolve the fat or oil into 1 mL chloroform. Include rancid oil or fat.
2. Add 2 mL of glacial acetic acid and 1 drop of 10% potassium iodide solution.
3. Mix well and leave for 5 min.
4. The presence of peroxides is denoted by the liberation of iodine.
E. Surfactants and diffusion demo-experiment (to be done as a class)
1.
Get Petri dishes and fill them with the following:
a.
Full cream
b.
50% cream
c.
Full milk
d.
50% milk
e.
10% milk
f.
3% milk
g.
skim milk
2.
Add one drop each of the food dyes near the edge of the dish. Keep the spots as far from one
another as possible.
3.
To all the plates, add a drop of dishwashing liquid simultaneously.
4.
Observe in which plate the colors move or travel the fastest.