Part A: Hypothesis and Data Collection You will prepare the following solutions for this activity:

milk and water
milk and lactase enzyme
milk and lactase enzyme heated to boiling
sucrose and water
sucrose and lactase enzyme
sucrose and lactase enzyme heated to boiling
You will test these solutions for the presence of glucose by using glucose test strips.

Question 1
Study the list of solutions. The glucose strips will change color when glucose is present in the solution. Use the diagram to predict whether the test strips will change color for the solutions listed. Write your prediction in the answer space.

an illustration showing the molecular structure of fructose, glucose, galactose, sucrose, and lactose

Question 2
In this part of the experiment, you’ll prepare and test three milk solutions: milk and water, milk and lactase enzyme, and milk and heated lactase enzyme.

Prepare

Use masking tape to label the three beakers: “milk,” “lactase solution,” and “heated lactase solution.”
Measure 60 milliliters of milk in the graduated cylinder (or ¼ cup of in a measuring cup. Pour it into the beaker labeled “milk.”
In the beaker labeled “lactase solution,” add one lactase tablet and 100 milliliters (or 1/2 cup) of cool or room-temperature water. Use the stirrer to dissolve the lactase tablet in the water.
Add 100 milliliters (or 1/2 cup) of water to the microwaveable container. Dissolve a lactase pill in the container. Put the solution in the microwave and heat it to boiling (about 2 minutes). Use oven mitts to remove the container. Pour the heated lactase solution into the beaker labeled “heated lactase solution” and let it cool.
Stay safe! Be careful while handling the boiled mixture to avoid spilling it on your hands.

Test

While you’re waiting for the lactase solution to cool, read the directions on the test strips. The test strips in the Edmentum lab kit will react to glucose within a few seconds. If you use different strips, the reaction time may vary. Now follow these steps to test the solutions. Record your data in the answer space.

Milk and water solution: Fill the first test tube one fourth full of milk. Fill the small graduated cylinder with water and gently add it to the milk in the test tube until the test tube is half full. Use the stirrer to thoroughly mix the solution. Then insert the test strip for 10 to 20 seconds. Look at the test strip, and record whether it changed color. Wash the stirrer.
Milk and lactase enzyme solution: Fill the second test tube one fourth with milk and one fourth with the lactase solution. Use the stirrer to thoroughly mix the solution. Insert the test strip for 10 to 20 seconds, and record whether it changed color. Wash the stirrer.
Milk and heated lactase enzyme solution: Fill the third test tube with one fourth milk and one fourth of the heated lactase solution. Use the stirrer to mix the solution. Insert the test strip for 10 to 20 seconds, and record whether it changed color.
Note: Keep the lactase and heated lactase solutions for the next part of the experiment.

Wash the “milk” beaker, the test tubes, and the stirrer. If you used paper cups as an alternative, throw them away.

Question 3
In this part of the experiment, you’ll test your three sucrose solutions: sucrose and water, sucrose and lactase enzyme, and sucrose and heated lactase enzyme. Follow the steps. Record your data in the answer space.

Collect three test tubes.
Fill the first test tube one fourth full of sugar. Fill your small graduated cylinder with water and add it to the test tube until the test tube is half full. Stir the solution until the sugar dissolves, and then insert the test strip for 10 to 20 seconds. Record whether the test strip changed color. Wash the stirrer.
Fill the second test tube one fourth full of sugar and one fourth full of the lactase solution. Thoroughly mix the solution. Insert the test strip for 10 to 20 seconds, and record whether it changed color. Wash the stirrer.
Fill the third test tube one fourth full of sugar and one fourth full of the heated lactase solution. Thoroughly mix the solution. Insert the test strip for 10 to 20 seconds, and record whether it changed color.
Pour the solutions down the drain. Remove the masking tape from the beakers. Wash the beakers, test tubes, and stirrer. If you used paper cups as an alternative, thrown them away.

Part B: Analyze and Extend

Question 1
How did your results match your predictions?

Question 2
Use the results of your experiment to explain why the color changed on some test strips but not others.

Question 3
Use your results to explain how temperature affects enzymes.

Question 4
People who are lactose intolerant lack the lactase enzyme. They often experience digestive problems when they eat dairy products. Do the results of your experiment support this scenario? Explain your response.

Question 5
How do your results show that digestive enzymes are crucial to maintaining homeostasis inside the body?