Educator's Guide (Grades 9-12) - Buffalo Museum of Science
Educator's Guide (Grades 9-12) - Buffalo Museum of Science
Educator's Guide (Grades 9-12) - Buffalo Museum of Science
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In the descriptions below, we have only included experiments that are quick to do and are therefore well-suited to<br />
demonstrations. However, it is <strong>of</strong>ten unavoidable that results—particularly those relating to protein digestion—can only<br />
be seen after one or several hours (if egg white is used).<br />
EXPERIMENT:<br />
Digestion <strong>of</strong> Fat<br />
Materials:<br />
Cooking oil, pancreatin, dilute sodium hydroxide, phenolphthalein solution.<br />
Test tubes, beakers, 1 Erlenmeyer flask with airtight stopper,<br />
300ml (or larger), measuring pipette (e.g. 5 ml).<br />
Preparation:<br />
I. Fill each <strong>of</strong> 2 test tubes with the same amount <strong>of</strong> water (approx. 5ml).<br />
Put approx. 50 mg (1 “spoon tip’s worth”) <strong>of</strong> pancreatin into one <strong>of</strong> these test tubes and shake into a suspension.<br />
II. Put approx. 200 ml <strong>of</strong> water and approx. 2ml <strong>of</strong> cooking oil into an Erlenmeyer flask.<br />
Seal the flask and shake it vigorously until an opaque milky liquid forms.<br />
Add 5 drops <strong>of</strong> dilute sodium hydroxide and 5 drops <strong>of</strong> phenolphthalein solution to this emulsion,<br />
while swirling the flask. The liquid is now a pink colour .<br />
Method:<br />
Divide the fat emulsion (II) equally between 2 beakers.<br />
Add the pancreatin suspension (I) to one <strong>of</strong> the beakers.<br />
For comparison, add only an equivalent amount <strong>of</strong> water to the second beaker .<br />
Observations:<br />
After a short time the contents <strong>of</strong> the fi rst beaker become colourless, whereas no change can be seen<br />
in the second beaker .<br />
Explanation:<br />
Pancreatin contains the enzyme lipase, which breaks up fat. The free fatty acids that result from the process neutralise<br />
the sodium hydroxide. In neutral and acidic conditions, phenolphthalein is colourless.<br />
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