EXPERIMENT 2: TESTING FOR GLUCOSE IN MILK SOURCES Many human babies consume lactose through breast milk. Lactase is used in this process as it is the enzyme required to breakdown lactose into glucose and galactose. However, certain populations lose the ability to break down lactose as they age. This is problematic as the body can’t properly digest lactose, and some communities around the world rely on milk products for a healthy diet. In this experiment, you will test for the presence of glucose in regular milk, lactose free milk, and an unknown solution using glucose test strips. PROCEDURE O 1. Use the permanent marker to label the three test tubes 1, 2, and 3. 2. Use the 100 mL graduated cylinder to measure and pour 25 mL of water into Test Tube 1. Key Technique 3. Using a pipette to transfer the milk, measure out 25 mL of lactose free milk using the 100 mL graduated cylinder. Pour the 25 mL of lactose free milk into Test Tube 2. Rinse the graduated cylinder with water. 4. Use the 100 mL graduated cylinder to measure and pour 30 mL of water into the 100 mL beaker. 5. Measure and mix 3 tsp. of the powdered milk into the 100 mL beaker. Make sure the powder and water are thoroughly mixed. 16. Using a pipette to transfer, measure out 25 mL of the liquefied powdered milk into the 100 mL graduated cylinder. Pour the 25 mL into Test Tube 3. 07. Immerse one glucose strip into each test tube for two seconds, ensuring that the pad on the strip is completely submerged. 8. Remove any excess liquid from the test strips by running the strip along the edge of the test tube. 19. Using your stopwatch, let the test strips sit for three minutes. 10. Match the color of each test strip to the color scale given in Figure 5 and record the concentrations in Table 2. concentration mg/dL 100 300 1000 3000 0 Figure 5: Glucose test strip concentrations. 11. Create a funnel for pouring powder using a sheet of paper. This funnel will be used in the following steps. | 12. Using the 1 tsp. measuring spoon, measure out and pour 1 tsp. of the unknown powder into Test Tube 1, 2 and 3 and gently swirl the contents to ensure mixing (your powder may get trapped on top of the liquid and will not mix, use any object that you can to push through the powder and liquid to force mixing). Wait 2 minutes. 13. Repeat Steps 7- 10. 14. Making sure that you have recorded your data, wash out one of the test tubes and add 1 tsp. of the unknown powder with 5 mL of water. Test this solution using the last glucose strip and observe if any changes occur. Post-Lab Questions 1. How was the glucose concentration in each sample affected by the addition of the unknown powder? 2. What can you conclude about the unknown powder based on your observations? 3. How do your observations relate to nutrition? 4. What are the positive and negative controls in this experiment? 5. How do the findings of this experiment relate to lactose intolerance? 6. Use online resources to look up and describe lactose intolerance. What causes it? What are the symptoms? Consult your professor for website guidelines and proper citation. EXPERIMENT 2: TESTING FOR GLUCOSE IN MILK SOURCES Data Sheet Table 2: Testing for Lactose in Samples Sample 1st round Glucose concentration (mg/dL) 2nd round Glucose concentration (mg/dL) 1 – Water 0 0 2- Lactose Free Milk 1000 300 3 – Powdered Milk 0 100
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