Lipase is a type of enzyme known as a hydrolase and is responsible for catalysing the hydrolysis of triglycerides (the substrate) into fatty acids and glycerol. It is referred to as a hydrolase because the reaction that it catalyses is a hydrolysis reaction in which large molecules are broken down into smaller ones with the addition of water. Lipase is a subclass of the esterases. Lipases usually involves in the digestion, transport and processing of dietary lipids in living organisms. Lipase is primarily produced in the pancreas, but is also in the mouth and stomach. Most people produce enough pancreatic lipase. But people with some disease such as cystic fibrosis and celiac disease may not have enough lipase to get the nutrition they need from food. As I had mentioned before, lipase catalyzes the breakdown of lipids by hydrolyzing the esters of fatty acids. Its function is important for the digestion and promoting absorption of fats in the intestines. Reaction of the lipase enzyme can be summarized as :
Lipids Fatty acids + Glycerol

This experiment was carried out to study the effect of temperature on rate of lipase’s activity of digesting fat into fatty acid and glycerol using a pH probe. The rate of lipase’s activity is the measure of how fast the lipase enzyme can catalyze the procedure of breaking down the lipid into triglyceride and fatty acids, causing the pH to decrease. Enzymes are sensitive to heat so does lipase. Lipase can be denatured by high temperature and extremes of pH. Both high temperature and extremes of pH change the bonds between amino acids in the enzyme, so changing its shape. This could stop the action of lipase. Addition of bile helps the action of lipase by promoting emulsification, allowing the lipid to mix more readily and reach the active sites of the enzyme more easily, speeding up the lipid digestion in the process.


1. Laber three test tubes 1 - 3.
2. Using a graduated pipette, place 5ml of milk into each test tube.
3. Then pipette 7ml of sodium carbonate solution into each test tube.
4. Pipette 1ml of 3% bile salts solution into test tubes 2 and 3.
5. Using a pipette, add 1ml of phenolphthalein solution to each tube until the mixtures are bright pink.
6. With the graduated pipette, place 1ml of lipase into tubes 1 and 3.
7. Add boiled lipase in test tube 2. Lipase should be added into each tube at the same time. Shake the tubes well so that the contents would mix.
8. Record the time taken for the contents in each test tube to change color from pink to white.


Lipid Digestion Data

Action of lipase on milk
Tube All three tubes contain milk, sodium carbonate and phenolphthalein and: Time taken to change from pink to white
1 Lipase only Slow
2 Boiled lipase and bile salts No changes
3 Lipase and bile salts Fast


The purpose of this experiment is to investigate the effect of temperature on the breakdown of lipid by the help of bile. Action of lipase on milk was tested using substances such sodium carbonate, an alkali, phenolphthalein which is an indicator and milk that contains fats. Test tube 1 is the control where only bile salt is not used. The result shows the actual time lipase takes to break down ordinary fats. Time taken for the test tube 1 to change color from pink to white is slower compared to others. This is because lipase breaks down the lipids into fatty acids and glycerol in a slower manner. Presence of fatty acids into the tube neutralised sodium carbonate and reduced the pH. So, the color of mixture in tube 1 is changed to white. Test tube 2 is used to show the denaturing effect of heat on lipase. High temperature destroyed the lipase’s structure, which in turn prevents its action. Boiled lipase was denatured due to the high temperature. This means that no fats are converted, even in the presence of bile salts. Thus, there is no changes in pH and the color of the mixture. Test tube 3 is a similar situation as occurs in our bodies. Lipase and bile salts were added into tube 3. Bile salts helps to speed the