Enzyme Review:
1. Label the parts of the graph below.
Return to the graph above and a line depicted the rate of the reaction with an enzyme present.
2. In the space below, draw an enzyme, its substrate and the product of the enzyme drive reaction.
3. Return to your drawings above, draw a competitive and noncompetitive inhibitor and indicate where each would bind to the enzyme molecule.
4. What is meant by an induced fit ?
a. The binding of the substrate in an energy requiring process.
b. A competitive inhibitor can out compete the substrate for the active site.
c. The binding of the substrate changes the shape of the active site, which can stress or bend substrate bonds.
d. The active site creates a microenvironment ideal for the reaction.
5. In an experiment, changing the pH from 7 to 6 resulted in an increase in product formation. From this we could conclude that
a. the enzyme became saturated at pH 6.
b. the enzyme’s optimal pH is 6.
c. the enzyme works best in a neutral pH.
d. the temperature must have increased when the pH
was changed to 6.
e. the enzyme was in a more active conformation at
pH 6.
6. In the metabolic pathway, A→ B → C → D → E, what effect would molecule E likely have on the enzyme that catalyzes A → B?
a. allosteric inhibitor
b. allosteric activator
c. competitive inhibitor
d. feedback activator
e. coenzyme
7. Draw the following with proper axes:
a. graph showing the effect of increasing temperature on the rate of reaction of an enzyme catalyzed reaction;
b. a graph showing the effect of substrate concentration on the rate of reaction of an enzyme catalyzed reaction.
8. Explain why each of the above graphs has the shape it has.
9. Zinc, an essential trace element, may be found bound to the active site of some enzymes. Such zinc ions most likely function as
a. a coenzyme derived from a vitamin
b. a cofactor necessary for catalysis
c. a substrate of the enzyme
d. a competitive inhibitor of the enzyme
e. an Allosteric activator of the enzyme
10. Consider the metabolic pathway shown below.
1 2 3 4
A → B → C → D → E
If there is end-product inhibition, which product (B to E) would inhibit which enzyme (1 to 4)?
ProductEnzyme
a.C4
b.B3
c.B4
d.E1
11. An experiment was conducted to measure the reaction rate of the human salivary enzyme α- amylase. Ten mL of a concentrated starch solution and 1.0 mL of α- amylase solution were placed in a test tube. The test tube was inverted several times to mix the solution and then incubated at 25oC. The amount of product (maltose) present was measured every 10 minutes for an hour. The results are in the table below.
Ti me (minutes) / Maltose Concentration (µM)0 / 0
10 / 5.1
20 / 8.6
30 / 10.4
40 / 11.1
50 / 11.2
60 / 11.5
a. Graph the data and calculate the rate of reaction for the time period of 0 to 30 minutes.
b. Explain why a change in the reaction rate was observed after 30 minutes.
c. Draw and label another line on the graph to predict the results if the concentration of α- amylase was doubled. Explain your predicted results.
d. Identify TWO environmental factors that can change the rate of an enzyme-mediated reaction. Discuss how each of those factors would affect the reaction rate of the enzyme.
12. Yeast cells are placed in an apparatus with a solution of sugar (a major nutrient for yeast metabolism). The apparatus detects bubbles of gas released by the yeast cells. The rate of respiration varies with the surrounding temperatures as indicated by the data below.
Temp. (oC) / 0 / 10 / 20 / 30 / 40 / 50 / 60 / 70Number of bubbles of gas produced per minute / 0 / 3 / 7 / 12 / 7 / 4 / 1 / 0
a. Graph the results. Determine the optimum temperature for respiration in the yeast.
b. Respiration is a series of enzyme-catalyzed reactions. Using your knowledge of enzymes and the data above, analyze and explain the results of the experiment.
c. Design an experiment to test the effect of varying pH of the sugar solution on the rate of respiration. Include a prediction of the expected results.
13. Urease is an enzyme that breaks down urea into ammonia and carbon dioxide. The ammonia produced causes the pH of the solution to rise. This reaction can be followed using a pH indicator or a pH probe.
In an experiment conducted by a student the time taken for the pH indicator, thymol blue, to change from yellow to blue was recorded at different temperatures.
a. Outline what the standard deviations reveal about the data from this experiment.
b. Outline the effect of temperature on the activity of urease enzyme.
c. State one factor that would need to be controlled in this experiment.
14. What happens in the active site of an enzyme?
15. Describe the induced fit model to explain enzyme function.
16. Which type of enzyme inhibition can be overcome by increasing substrate concentration?
17. What is a coenzyme?
18. What impact will high temperatures have on enzymes?
19. What is a noncompetitive inhibitor?
20. What is end product inhibition?