The Young Scientist Program
http://ysp.wustl.edu
Washington University Medical School
Funding provided by The Leon Lowenstein Foundation
Enzyme Catalysis III: Dissolving Gelatin with Pineapples
Chemistry Teaching Team
Main Concepts:
Enzymes and substrates
Module Overview: An enzyme is a catalyst. A catalyst helps a reaction to occur, but is not changed during the course
of the reaction. All living organisms use enzymes to get energy from their food. Some enzymes break apart proteins
into smaller chunks. Gelatin is a common substance that is made up of proteins. Gelatin is added to various foods to
give them a characteristic consistency. Gelatin cannot be mixed with fresh pineapple, however.
Materials:
Unflavored gelatin packets
Test tubes and racks
Sharpie markers
Fresh pineapple cubes
Canned pineapple cubes
Safety: students do not need to use gloves or goggles for protection in this experiment. The students should not eat
anything used in this experiment, as the food will have come in contact with lab equipment and may be contaminated
with chemicals.
Methods/Protocol:
1. Heat 1 cup of water on the hot plate to boiling in a glass beaker. Remove from the hot plate (using a hot pad) and
add 1 packet of gelatin powder. Allow the gelatin to cool slightly, but do not allow it to solidify yet.
2. Label 3 test tubes and do the following:
tube 1: pour in ~5 mLs warm gelatin
tube 2: place a few chunks of fresh pineapple in the tube, and pour ~ 5 mLs of warm gelatin over
tube 3: place a few chunks of canned pineapple in the tube, and pour ~5 mLs of warm gelatin over
3. Place the three tubes in a large beaker full of ice to speed the gelatin solidification. When tube 1 has solidified,
take out all three tubes and compare them.
Discussion Questions:
1. What happened to the gelatin in the test tubes?
The Young Scientist Program
http://ysp.wustl.edu
Washington University Medical School
Funding provided by The Leon Lowenstein Foundation
The gelatin solidified in tubes 1 and 3, but remained liquid in the tube with the fresh pineapple.
2. What is in the pineapple that could keep the gelatin from solidifying?
The pineapple contains an enzyme that can break apart proteins. When it is mixed with the gelatin, the enzyme chops
the gelatin proteins into smaller pieces, which prevents them from making a solid.
3. Why didn’t the canned pineapple prevent the gelatin from solidifying?
The canned pineapple also has the enzyme, but the enzyme has been inactivated by the high temperature and pressure
used to preserve the fruit. The gelatin can still solidify around the pineapple.