Many human babies consume milk sugar-the disaccharide lactose through breast milk. Lactase is the enzyme required to bre

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Many Human Babies Consume Milk Sugar The Disaccharide Lactose Through Breast Milk Lactase Is The Enzyme Required To Bre 1 (57.55 KiB) Viewed 13 times

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Many human babies consume milk sugar-the disaccharide lactose through breast milk. Lactase is the enzyme required to break lactose down into the monomers glucose and galactose (see Figure 1). CH₂OH OH OH 88. CH₂OH OH OH OH + H₂O lactase CH₂OH ОН, 8 OH -O. OH OH Galactose HO CH₂OH OH -O. OH OH Glucose OH Lactose Figure 1. Hydrolysis of Hydrolysis of lactose is necessary so that the monosaccharide monomers can be absorbed. So, all humans produce the protein lactase as infants. However, as we get older the genes that are made into proteins (our gene expression) changes. One example of this is that certain people lose the ability to break down lactose as they age. Historically, this has been problematic for humans. Without lactase the body can't digest lactose without serious digestive problems, and some communities around the world traditionally rely on milk products as a major part of their diet. Modern humans are in luck, however, as we now have lactase in pill and powder form! Commercially produced lactase is extracted from certain yeasts and molds and included in products such as Lactaid™". In this experiment, you will test for the presence of glucose in 3 different solutions: water, regular milk, lactose free milk. You'll test each solution before and after adding a solution you make with the included "unknown powder." The presence of glucose can be detected with color-changing indicator test strips. Note that the glucose test strips only detect glucose when it is a monomer, not when it exists within a larger molecule such as lactose. Simply put, lactose molecules will not react with the chemicals in the test strip. Thus, a negative result means no unbound glucose is present, while a positive result reveals that it is. Before beginning this experiment, review the background information on nutrition provided by eScience.

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. Repeat Steps 7-10. Making sure that you have recorded your data in Table 2, 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. 13. Note the type of lactose-free milk you used here: unsweetened almond milk Table 2: Testing for Glucose in Samples Before and After Addition of Unknown Powder Sample 2nd round Glucose concentration (mg/dL) 1- Water 2- Lactose Free Milk 3- Powdered Milk 1st round Glucose concentration (mg/dL) 100 10 100 100 150 Post-Procedure Questions 14. Identify the independent variable in the experiment. [Hint: The independent variable is what is manipulated (changed). It will often include an experimental group and at least 1 control group. Group groups provide standards for comparison. A negative control shows you the results you get if the independent variable has no. effect on the dependent variable. A positive control shows you the results you get if the independent variable does have an effect on the dependent variable.] a. independent variable: b. negative control: c. positive control: 15. Identify the dependent variable in the experiment. [Hint: The dependent variable is what you think will change if the independent variable is changed. You may have learned the dependent variable is what you measure. This is true but it's also true that many times the independent is measured as well to be sure that it actually changed during the experiment.] 16. How was the glucose concentration in each sample affected by the addition of the unknown powder? Be specific. (This means describe the information in your data table in writing in

addition to saying qualitatively how the level changed.) 17. Given what you learned about lactose and lactase in the Introduction to this lab, what do your results suggest about the make-up of the unknown powder? 18. Where does the information for how to build the lactase enzyme come from? 19. Why are human babies always born with the ability to chemically digest lactose? Another way of thinking about this is to imagine what would happen if a baby was born without this ability 100 years ago (before lactose-free baby formula was available). 11

Materials 7 Glucose Test Strips (NOT pH strips) 1.5 tsp. Powdered Milk 3 tsp. Unknown Powder "Lactose Free Milk (All of these are lactose-free: soy, almond, rice, oat, hemp "milks") *Paper (to create a funnel) "Water Note: You must provide the materials listed in "red. Before beginning, WATCH: Key Technique: How to Read a Meniscus PROCEDURE S Labware 100 mL Beaker 100 mL Graduated Cylinder 3 Transfer Pipettes 3 Test Tubes Test Tube Rack *Measuring Spoons *Stopwatch/Timer "Permanent Marker Use the permanent marker to label the three test tubes 1, 2, and 3. Use the 100 mL graduated cylinder to measure and pour 25 mL of water into Test Tube 1. 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 thoroughly with water. Use the 100 ml graduated cylinder to measure and pour 30 mL of water into the 100 mL beaker. Measure and mix 3 tsp. of the powdered milk into the 100 mL beaker. Make sure the powder and water are thoroughly mixed. 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. Step 7: Immerse one glucose strip into each test tube for two seconds, ensuring that the pad on the strip is completely submerged. Step 8: Remove any excess liquid from the test strips by running the strip along the edge of the test tube. Step 9: Using your stopwatch, let the test strips sit for three minutes. Step 10: Match the color of each test strip to the color scale given to the right and record the concentrations in Table 2. If the color you observe is intermediate to the numbered colors at left, record the number halfway 0 concentration mg/dL 100 300 1000 3000 between the 2 values. For example, if you observe a color that is between the first 2 squares, record 50 mg/dL. Create a funnel for pouring powder using a sheet of paper. This funnel will be used in the following steps. 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