Task: At this station, you will be collecting and analzying data about enzymes activity.

Materials

• Glucose solution
• 3 Unknown Disaccharide Solutions: A, B, and C
• Enzyme Solution
• Indicator strips for glucose
• Spot plate (depression plate)

Background

Disaccharides are chemically changed to simple sugar molecules by enzymes. In this exercise, you will determine whether a certain enzyme is specific for only one disaccharide.

Read through all the directions before beginning.

Directions

After reading the directions, set up a rough copy of a data table to record your observations.

1. Add two drops of the known glucose solution to Well #1 of the spot plate. Insert the end of one strip of the glucose test strip indicator. Wait 15-30 seconds before reading the results. Record your observations.

2. Add one drop of the enzyme solution to Well #2 of the spot plate. Repeat the above test with the test strips and record your observations.

3. Add two dropw of each of the unknown disaccharide solutions to the spot plate as follows:
   "A" in spot #3, "B" in spot #4, "C" in spot #5

   Test each with a different indicator strip. Record your observations.

4. Add two drops of each of the unknown disaccharide solutions to the spot plate as follows:
   "A" in spot #6, "B" in spot #7, "C" in spot #8

   To each sample of unknown disaccharide, add one drop of the enzyme. Wait about two minutes and then test with the indicator strip. Record your observations.

Observations:

In the space below, draw an appropriate table to record your observations.

1. Using complete sentences, explain why testing well #2 is a necessary step in the procedure.

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2. Explain in complete sentences, how this experiment shows that enzymes are specific for only one substrate?

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3. If the enzyme used in this experiment was lactase, name the specific substrate on which it acts.

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4. If the enzyme used in this experiment was lactase, which spot contained that substrate?

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5. Using complete sentences, explain your answer to question 4.

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6. Write the word equation for the chemical reaction that is catalyzed by lactase.

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7. Is the reaction in this activity dehydration synthesis or hydrolysis (digestion)?

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8. Using complete sentences, explain your answer to question 7.

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NYS Alternative Assessment in Science Project
NSF Grant #MDR-9154506
Copyright, April 1996
The State University of New York
The State Education Department
Albany, New York 12234