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Enzymes: Temperature, pH, and Specificity Hands-On Labs, Inc. Version 42-0054-00-03 solution
Exercise 1: Enzyme Specificity
Data Table 1.
| Well Plate | Contents | Glucose Concentration |
| A | 3 drops 5% sucrose + 3 drops dH2O | Neg |
| B | 3 drops milk + 3 drops dH2O | Neg |
| C | 3 drops 5% sucrose + 3 drops lactase | Neg |
| D | 3 drops milk + 3 drops lactase | 15/30 |
| E | 3 drops 20% glucose + 3 drops dH2O | 110 |
Questions
A. Explain why a glucose test strip may be used to determine the enzymatic activity of lactase.
B. In this exercise, five reactions were performed. Of those reactions, two were negative controls and one was a positive control. Describe which of the reactions were controls and if they provided the expected results. Use the data in Data Table 1 to support your answer.
C. Did the lactase enzyme show specificity? Support your answer by comparing your data for lactose and sucrose.
Exercise 2: Enzymes, Temperature, and pH
Data Table 2
| Lactase Tube | Temperature (°C)e (°C) | Time (minutes)) | Glucose Concentratione Concentration |
| Cold | 7C | 5 minutes | 5/15 |
| 10 minutes | 5/10 | ||
| 15 minutes | 5 | ||
| 20 minutes | 5 | ||
| Room | 21C | 5 minutes | 5/15 |
| 10 minutes | 5/10 | ||
| 15 minutes | 15 | ||
| 20 minutes | 15 | ||
| Hot | 81C | 5 minutes | Negative |
| 10 minutes | Negative | ||
| 15 minutes | Negative | ||
| 20 minutes | Negative | ||
Data Table 3. Enzymes and pH.
| Well Plate | Contents | Glucose Concentration |
| 1 | 3 drops pH 3.5 buffer + 2 drops lactase + 2 drops milk | 15 |
| 2 | 3 drops pH 5.0 buffer + 2 drops lactase + 2 drops milk | 15 |
| 3 | 3 drops pH 6.8 buffer + 2 drops lactase + 2 drops milk | 5 |
| 4 | 3 drops pH 11.5 buffer + 2 drops lactase + 2 drops milk | Negative |
Questions
A. Describe the relationship between temperature and the enzymatic activity of lactase. Of the three temperatures tested, which is the optimal temperature for enzyme activity? Use the results in Data Table 2 to support your answer. Hypothesize how the structure of the lactase relates to the results in Data Table 2.
B. Describe the relationship between pH and the enzymatic activity of lactase. Of the pH values tested, which is the optimal pH? Use the results in Data Table 3 to support your answer. Hypothesize how the structure of the lactase relates to the results in Data Table 3.
C. In the body, the lactase enzyme functions to break down lactose during digestion. In light of this, what approximate pH would you expect lactase to be most active? Did your results in Data Table 3 agree with or disagree with your expectations for the optimal pH?
D. In the Background, the presence of naturally occurring enzymes in fruits and vegetables was discussed. Using your results from this exercise as a basis to guide your thoughts, do you think that cooked, frozen, or raw fruits and vegetables would contain the most active enzymes?
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