Experimental Design

Purpose:

• To determine how the pH affects the glucose levels caused by an enzyme-driven reaction

Hypothesis:

• The test tubes containing solutions of ph 5, 7 to contain highest levels of glucose.

Materials:

• 5 test tubes
• 5 rubber stoppers
• 1 marker
• 1 roll of masking tape
• 50 mL of 2% Milk (Lactose source)
• 10 mL of solution pH 3
• 10 mL of solution pH 5
• 10 mL of solution pH 7
• 10 mL of solution pH 9
• 10 mL of solution pH 11
• 1 test tube rack
• 2 Graduated Cylinder
• Lactase Drops (10 drops per test tube)
• 5 Glucose strips (indicators)

Procedure:

1. Label the test tubes from 1 to 5
2. Fill one test tube with 10 mL of 2% milk
3. Add  10 mL of a solution of different pH to a test tube (pH level must be different for each test tube)
4. Add 10 drops of Lactase to a test tube.
5. Place a rubber stopper on the test tube and shake well.
6. Wait 2 minutes before applying glucose strips into the solution
7. Record data
8. Repeat process for all test tubes

Data + Observations:

• When testing the solution at pH 3, the reaction was not visible after adding 10 drops of Lactase
• All test tubes caused the glucose strips to produce a brown colour, which indicated that the solution has a high level of glucose after adding the lactase drops
• All glucose strips did not turn brown at the same time. Some took longer than others to produce a brown colour

Analysis + Conclusion:

• After consulting with each other, we have come to the realization that we may have done the experiment incorrectly or improperly. When measuring the glucose levels in the solution, we found all of the glucose strips to have the same brown colour that tells us all of the solutions had a pH in the range of 7-8 which indicates they were neutral or slightly basic
• Since all test tubes yielded the same results, we have concluded that the levels of pH have little to no effect on the levels of glucose in 2% milk. The results did not support our hypothesis, most likely due to our improper execution of the lab. We have also considered several factors that may have produced unnatural results, which caused our lab to be somewhat incorrect. Several factors include:

• • Different amount of lactase drops for each test tube
  • Timing the reaction of the glucose strips
  • Excessive volumes of each solvent
  • Lack of a presence of a control group

• The intent of this lab is to observe how lactase breaks down a disaccharide into glucose and galactose. If done correctly, our group would have yielded better results, of which would allow us to determine how the pH of a solution affects glucose levels in a solution