Virtual Lab: Enzyme Controlled Reactions

Name ______Period ______

Log on to http://www.mhhe.com/biosci/genbio/virtual_labs/BL_11/BL_11.html

A. Read the purpose. Summarize the purpose

B. Read the objectives. What are you going to learn?

C. Read the procedure. What do you need to do?

D. Summarize the video shown on the TV/VCR.

E. Conduct the experiment. Record your data on the number of product molecules formed per minute obtained from the virtual lab.

Table 1: Number of Molecules of Product per minute (x106) Amount of pH 3 pH 5 pH 7 pH 9 pH 11 Substrate (Lactose) 0.5 g

1.0 g

2.0 g

4.0 g

8.0 g

F. Graph your results on graph paper 1. Title your graph 2. On the x-axis – title: Amount of substrate units: (grams) 3. On y axis – title: # product molecules per min 4. Enter all information labeling data sets by the pH

G. Answer the following questions by typing the letter of your option next to the question.

1. Identify the dependent and independent variables (hint: there are two independent variables you investigated, but only one dependent variable.)

2. Describe the relationship between substrate and the product. What happens when you increase the amount of substrate? Predict what would happen if you used 20.g of substrate and explain your reasoning behind the prediction.

3. Explain why the maximum initial reaction rate cannot be reached at low substrate concentrations. 4. What is the optimum pH level for this enzyme? How do you know? Make a prediction about what you think the reaction rate would look like a pH = 2. Explain why do you think that will happen?

5. Enzymes function most efficiently at the temperature of a typical cell, which is 37 degrees Celsius. Increases or decreases in temperature can significantly lower the reaction rate. What does this suggest about the importance of temperature-regulating mechanisms in organisms? Explain.

6. Which of the following does NOT apply to an enzyme: a. Catalyst b. Inorganic c. Protein d. All of the above apply to an enzyme

7. When an enzyme catalyzes a reaction: e. Substrate(s) bind in the active site f. Products bind in the active site g. The shape of the enzyme remains unchanged h. The enzyme is consumed by the reaction

8. Which of the following would interfere most with the ability of an enzyme to catalyze a reaction? i. Reduced concentration of substrate available j. Reduced concentration of product available k. Increased concentration of substrate available l. A change in the pH

9. Feedback mechanisms regulate the rate of enzyme activity, effectively “turning off” an enzyme in a reversible way until more product is needed. Which of the following would be most effective as a feedback mechanism? m. Reduced concentration of product n. Increased concentration of substrate o. A change in pH p. Temporary binding of a non-substrate molecule in the active site

10. Is the action of the enzyme illustrated in the video: a. Anabolic or catabolic? b. Endergonic or exergonic?

11. Why is enzyme activity similar to, but not exactly like, a “Lock” and “Key”?

12. List two changes you could make in the experimental conditions or variables in this experiment.