AP®BiologyCollege BoardExam QuestionsUnit 3: Cellular EnergeticsEnzymes

Enzymes (College Board AP® Biology)

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Enzymes

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Enzymes

1a4 marks

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 25°C. The amount of product (maltose) present was measured every 10 minutes for an hour. The results are given in the table below.

Time (minutes) 

Maltose Concentration (μM)

0

0

10

5.1

20

8.6

30

10.4

40

11.1

50

11.2

60

11.5

Graph the data on the axes provided and calculate the rate of the reaction for the time period 0 to 30 minutes. 

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1b2 marks

Explain why a change in the reaction rate was observed after 30 minutes. 

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1c2 marks

Draw and label another line on the graph to predict the results if the concentration of α-amylase was doubled. Explain your predicted results. 

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1d4 marks

Identify TWO environmental factors that can change the rate of an enzyme-mediated reaction. Discuss how each of those two factors would affect the reaction rate of an enzyme. 

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2a1 mark

Fireflies emit light when the enzyme luciferase catalyzes a reaction in which its substrate, D-luciferin, reacts to form oxyluciferin and other products (Figure 1). In order to determine the optimal temperature for this enzyme, scientists added ATP to a solution containing D-luciferin, luciferase, and other substances needed for the reaction. They then measured the amount of light emitted during the first three seconds of the reaction when it was carried out at different temperatures.

D-Luciferin + O2 + ATP rightwards arrow with Lucifefase on top Oxyluciferin + CO2 + AMP + PPi + Light

Figure 1. Light is emitted as a result of the reaction catalyzed by luciferase.

Describe a characteristic of the luciferase enzyme that allows it to catalyze the reaction.

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2b1 mark

Identify the dependent variable in the experiment.

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2c1 mark

State the null hypothesis for the experiment.

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2d1 mark

A student claims that, as temperature increases, there will be an increase in the amount of light given off by the reaction in the first three seconds. Support the student's claim.

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