Look at these molecular structures. Use the molecular structures to predict which of the six solutions will test positive for glucose. Write your prediction in the answer space. Provide the reasoning behind your prediction.

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Question 2
First, Demetri will test the three solutions containing milk (lactose).

He begins the experiment by preparing the lactase enzyme solutions. In one beaker he dissolves 1 lactase tablet in 100 mL of water at room temperature. He stirs the mixture until the tablet has dissolved completely. He repeats this process in a second beaker, and then heats the beaker until the solution is boiling.

Demetri then tests these three milk (lactose) solutions for the presence of glucose:

milk in water
milk and lactase enzyme in water
milk and heated lactase enzyme in water
Test Tube 1 - Milk (Lactose): Demetri fills the first test tube one-quarter full of milk. Then, he slowly adds water to the milk until the test tube is three-quarters full. Using the stirrer, Demetri thoroughly mixes the solution. Then he inserts the test strip for 30 seconds and records its color.

Test Tube 2 - Milk (Lactose) and Lactase Enzyme: Demetri fills the second test tube one-quarter full with milk. He then adds the lactase-and-water solution until the test tube is three-quarters full. He uses a stirrer to thoroughly mix the solution. Next, Demetri inserts the test strip for 30 seconds and records its color.

Test Tube 3 - Milk (Lactose) and Heated Lactase Enzyme: Demetri fills the third test tube one-quarter full with milk. He then adds the heated lactase-and-water solution until the test tube is three-quarters full. After stirring, Demetri inserts the test strip for 30 seconds and records its color.

According to the test strips, which of these milk solutions contained glucose?

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Question 3
Next, Demetri tests these three sugar (sucrose) solutions for the presence of glucose:

sugar and water
sugar and lactase enzyme in water
sugar and heated lactase enzyme in water
Test Tube 4 - Sugar (Sucrose): Demetri fills the fourth test tube one-quarter full of sugar. He then adds water to the test tube until it is three-quarters full and stirs until the sugar dissolves. Demetri then inserts the test strip for 30 seconds and records its color.

Test Tube 5 - Sugar (Sucrose) and Lactase Enzyme: Demetri fills the fifth test tube one-quarter full of sugar. He then adds the lactase-and-water solution until the test tube is three-quarters full. He thoroughly mixes the solution and inserts the test strip for 30 seconds. Demetri then records the color of the test strip.

Test Tube 6 - Sugar (Sucrose) and Heated Lactase Enzyme: Demetri fills the sixth test tube one-quarter full of sugar. He then adds the heated lactase-and-water solution until the test tube is three-quarters full. He thoroughly mixes the solution and inserts the test strip for 30 seconds. Demetri then records the color of the test strip.

According to the test strips, which of these sugar solutions contained glucose?

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Part B: Analyze and Extend
Question 1
How did Demetri's results match your predictions?

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

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Question 3
Use Demetri's results to explain how temperature affects enzymes.

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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 Demetri's experiment support this scenario? Explain your response.

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

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