Science project

Digestive Enzymatic Activity and Lipid Digestion


Does raising the temperature affect the ability of lipase to break-down oil without bile? Is there any observable effect in oil break-down in the presence of lipase at a specific temperature? 


  • Seven 20 x 150 mm test tubes
  • Test tube holder
  • Bile salt
  • Powdered lipase
  • ¼ teaspoon 
  • Water
  • Cooking oil
  • Clock or watch
  • Cooking pot
  • Small medicine thermometer
  • Coffee stirring sticks
  • Heat source
  • Safety goggles
  • Latex gloves
  • Bile salt may cause eye and skin irritation. Avoid inhalation. If eye contact occurs, flush with water. Prolonged contact with bile dust may cause respiratory irritation, allergic or asthmatic reaction. Harmful if swallowed. Use with adequate ventilation. Wash hands thoroughly after handling. Keep the bottle closed when not in use.
  • Lipase may cause eye and skin irritation in some individuals. It is moisture sensitive keep the bottle closed when not in use. 
  • Wash hands with soap and water immediately after completing the project, even if you wore gloves.


  1. Fill a test tube ½ full with water at room temperature. Add a few drops of oil. This test tube will serve as the control.
  2. Add ¼ teaspoon (1 ml) of bile salt and ¼ teaspoon powdered lipase to the test tube.
  3. Shake the test tube in order to mix the contents thoroughly.
  4. Insert a thermometer and record the temperature.
  5. Take notes describing the mixture in the test tube.
  6. Allow the tube to sit undisturbed for 20 minutes, and then check the temperature. Take notes on the mixture again.
  7. Take a second test tube and repeat the same procedure, except do NOT add bile salt.
  8. Insert a thermometer.
  9. Place the test tube in a pot of water
  10. Heat the water until the contents in the test tube reach 30 degrees C.
  11. Record the temperature and describe the mixture in the test tube after 20 minutes.
  12. Repeat the same procedure for the following temperatures (in degrees C): 40, 50, 60, 70, and 80.
  13. Use the following characteristics and a rough rating system when describing the lipase enzymatic action on the oil: “distinct layers 0%,” “globular droplets 25%,” “very tiny drops 75%,” “uniform homogeneous mixture 100%”. 
Test Sample #

Initial Temperature  

Observations 20 minutes later  

% Oil break-down  

 Room Temp
      30o C
      40o C
      50o C
      60o C
      70o C
      80o C
  1. Using graph paper or a computer equipped with Excel® visually display the data by plotting a line or bar graph comparing temperature verses relative lipid break down activity.
  2. The numerical values for % lipid break-down activity are displayed along the Y-axis verses the various measured temperatures along the X-axis. 
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