Since digestive enzymes actually function outside of the body cells in the digestive tract, their hydrolytic activity can be studied in a test tube. We studied starch digestion by salivary amylase, trypsin digestion of protein and pancreatic lipase digestion of fats. The goal of these tests was to understand the optimal environmental conditions needed for digestive enzymes to function. Additionally, it was the goal of the above experiments to learn the role of temperature and pH in the regulation of enzyme activity.
Starch Digestion by Salivary Amylase--Relevant Observations:
Salivary amylase and pancreatic amylase break down starch.
Boiling the mixtures denatures the enzymes and therefore starch is not reduced to sugar.
The pH of 7 is optimal for reducing starch to sugar.
If the pH is too high or too low starch and sugars will remain present.
Protein Digestion by Trypsin--Relevant Observations:
Trypsin breaks down protein.
When the substrate, BAPNA, was added to the test tubes containing Trypsin, we learned that hydrolysis had occurred.
Emulsification of Bile and Fat Digestion by Lipase--Relevant Observations:
Bile emulsifies fats. Emulsified fats provide a larger surface area for enzymatic activity.
When bile salt is added to the test tube with vegetable oil, the bile salt acts as a detergent and emulsifies the fat so that the surface area was greater, allowing the greater enzymatic activity.
In the case of the Pancreatic Lipase, we learned that fats are digested by fatty acids during hydrolysis, they will lower the pH of the sample they are in. Litmus cream turns from blue to pink if the solution is acidic.
Hypotheses: Hydrolytic enzymes hydrolyze only a small group of substrate molecules, and specific environmental conditions are necessary for it to function optimally.
Materials and Methods:
Test tubes and test tube rack
Water bath set at 37 degrees C
Ice water bath
Chart to record results
Dropper bottle of distilled water
Dropper bottles of: 1% amylase, 1% boiled starch solution, 1% maltose solution, Lugol’s iodine solution (IKI), Benedict’s solution.
Dropper bottles of 1% trypsin and .01% BAPNA solution
Dropper bottles of: 1% pancreatic solution, litmus cream, .1 N HCL, vegetable oil
Directions for conducting the experiment:
1. Obtain a test tube rack, 10 test tubes, and a wax marking pencil. Obtain a dropper bottle of distilled water and dropper bottles of maltose, amylase and starch solutions.
2. To test tube 1A; add 3 drops of starch and 3 drops of water.
3. To test tube 2A; add 3 drops of amylase and 3 drops of water.
4. To test tube 3A; add 3 drops of maltose and 3 drops of water.
5. To test tube 4A; add 3 drops of amylase then boil for 4 minutes then add 3 drops of starch.
6. To test tube 5A; add 3 drops of amylase and 3 drops of starch.
7. Incubate the 5 test tubes for 1 hour at 37 degrees C. Shake test tubes periodically.
8. Obtain a spot plate and dropper bottles of Lugol’s solution and Benedict’s solution. Set up the boiling water bath using a hot plate, boiling chips and a 250 ml beacker.
9. Mark 5 depressions of the spot plate 1A-5A for sample identification.
10. Pour about a drop of the sample from each of the tubes 1A-5A into the appropriately numbered spot. Into each sample drop, place a drop of Lugol’s IKI solution.
11. Into the remaining mixture in each tube, place 3 drops of Benedict’s solution. Put each tube into the beaker of boiling water