Digestive Enzymatic Activity and Lipid Digestion

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Updated on Jul 30, 2013

Many people (especially those with gall bladder insufficiency, or who have had their gall bladder removed) have difficulty digesting fats and oils. This is because they lack the bile salts needed for efficient digestion, and therefore lipase (an enzyme that processes fats)is unable tobreakdown these substances. This deprives the individual of manyhealthy benefits of certainfats and oils. An indication of insufficient oil digestion and absorption, for example, is dry skin, hair and nails.

Fats and oils are complex moleculesand because they do not dissolve in water. These molecules enter the small intestine in a congealed mass. Lipase is a water-soluble enzyme and can only attack the surface of the these molecules. To overcome this problem the digestive system uses bile, produced in the liver but stored in the gallbladder, which enters the duodenum via the bile duct. Bile emulsifies fats,breakingthemup into small droplets which then become suspended in the watery contents of the digestive tract.Emulsification allows lipase to gain easier access to these lipid moleculesand digest them completely.


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?‚Äč


  • 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, evenif 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 teaspoonpowdered lipase to thetest tube.
  3. Shake the test tube in order to mix the contents thoroughly.
  4. Insert a thermometer and record the temperature.
  5. Take notes describingthe mixture in the test tube.
  6. Allow the tube to sit undisturbed for 20 minutes, and then check the temperature. Take notes onthe 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 reach30 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. Usethe following characteristicsand a roughrating 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.
Mike Calhoun is a consultant for the National Science Teachers Association, a veteran science teacher, and hosts an online science website. Over the years Mike has studied trends in science, education, and finance, conducting research, developing programs, and writing articles on these topics.

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