AP BIO. UNIT 3 COLLEGE BOARD
EXAM QUESTIONS AND ANSWERS
Researchers investigated the influence of environmental pH on the activity of
peroxidase, an enzyme that catalyzes the conversion of hydrogen peroxide to water
and oxygen gas. In an experiment, the researchers added a hydrogen peroxide
solution containing guaiacol to several identical test tubes and adjusted the solution
in each test tube to a different pH. The researchers included the guaiacol because it
caused the solutions to change color as the reactions proceeded, which the
researchers relied on for measuring reaction rates. Finally, the researchers added
the same amount of peroxidase to each test tube and measured the rate of each
reaction at 23°C. The results of the experiment are represented in Figure 1.
One of the researchers proposes using oxygen gas production to measure reaction
rates. Which of the following statements best justifies the use of the proposed
modification as a way of creating an appropriate - ANSWER-The experiment can be
repeated without guaiacol, which will reveal the effect of guaiacol on the reaction
rates.
Aminolevulinate dehydratase (ALAD) is an enzyme that relies on zinc as a
coenzyme. A zinc ion binds to the ALAD active site, where it forms favorable
interactions with the side chains of three amino acids. Researchers have found that
substituting a lead ion for a zinc ion in the ALAD active site causes inhibition of
ALAD.
Which of the following statements best helps explain how the lead ion causes
inhibition of ALAD? - ANSWER-It changes the three-dimensional structure of the
active site so that ALAD is no longer compatible with its substrate.
Acetylcholinesterase (AChE) is a protein that catalyzes the conversion of
acetylcholine to acetate and choline. When the concentration of AChE in an aqueous
solution is held constant, the rate of the reaction catalyzed by AChE increases with
increasing concentrations of substrate. At low concentrations of acetylcholine, a
small increase in the substrate concentration results in a large increase in the
reaction rate. At high concentrations of acetylcholine, however, a large increase in
the substrate concentration results in only a small increase in the reaction rate.
Which of the following statements correctly explains the observed effect of the
acetylcholine concentration on the rate of the enzyme-catalyzed reaction? -
ANSWER-The active site of AChE is specific for acetylcholine, and only one
substrate molecule can occupy the active site at a time.
A researcher proposes a model to explain how enzyme-substrate interactions
determine enzyme specificity. The model is based on the idea that substrate
molecules form favorable interactions with the amino acid side chains in an enzyme's
active site.
Based on the model, which of the following statements best explains an enzyme's
specificity for a particular substrate molecule? - ANSWER-A molecule with negative
charges interacts with positively charged side chains in the enzyme's active site.
, Catalase is an enzyme found in yeast cells that facilitates the chemical breakdown of
hydrogen peroxide to water and oxygen gas. An experiment was conducted to
determine the effect of pH on catalase function. Five buffer solutions of varying pH
(2, 4, 6, 8, and 10) were prepared and added to separate test tubes. Hydrogen
peroxide (H2O2) was added to each test tube. Yeast was added, and the reactions
were timed. After 1 minute the amount of oxygen gas released was determined by
measuring the foam layer produced in each test tube. Figure 1 illustrates the
experimental setup.
A set of five additional test tubes were prepared and used as controls. Which of the
following best describes the contents expected to be contained in one of the five
control test tubes? - ANSWER-pH 4 buffer solution and hydrogen peroxide only
A student designs an experiment to investigate the influence of temperature on
enzyme function. The student's plan is presented in Table 1. Which test tubes are
controls in the experiment?
Test Tube Substrate Added Enzyme Added Temperature (°C)
1 Yes No 10
2 Yes Yes 10
3 Yes No 20
4 Yes Yes 20
5 Yes No 30
6 Yes Yes 30
7 Yes No 40
8 Yes Yes 40 - ANSWER-Test tubes 1, 3, 5, and 7
A researcher designs an experiment to investigate whether soil bacteria trigger the
synthesis of defense enzymes in plant roots. The design of the experiment is
presented in Table 1. For each group in the experiment, the researcher will
determine the average rate of change in the amount of defense enzymes in the roots
of the seedlings.
Group Number of Seedlings Type of Soil Treatment Solution
1 10 Sterile potting soil Contains actively reproducing soil bacteria
2 10 Sterile potting soil Contains heat-killed soil bacteria
3 10 Sterile potting soil Contains no soil bacteria
Which of the following statements best helps justify the inclusion of group 2 as one of
the controls in the experiment? - ANSWER-It will show whether the changes
observed in group 1 depend on the metabolic activity of soil bacteria.
Pectinase is a protein that catalyzes the breakdown of pectic polysaccharides in
plant cell walls. A researcher designs an experiment to investigate the effect of
salinity on the ability of pectinase to lower the activation energy of the reaction
involved. The design of the experiment is presented in Table 1. For each test tube,
the researcher will measure the amount of product formed over 20 minutes.
Test Tube Sodium Chloride Concentration (molar) Temperature (degrees C)
Substrate Added Pectinase Added
1 0 23 Yes No
2 0 23 Yes Yes
3 0.5 23 Yes No
4 0.5 23 Yes Yes
5 1.0 23 Yes No
EXAM QUESTIONS AND ANSWERS
Researchers investigated the influence of environmental pH on the activity of
peroxidase, an enzyme that catalyzes the conversion of hydrogen peroxide to water
and oxygen gas. In an experiment, the researchers added a hydrogen peroxide
solution containing guaiacol to several identical test tubes and adjusted the solution
in each test tube to a different pH. The researchers included the guaiacol because it
caused the solutions to change color as the reactions proceeded, which the
researchers relied on for measuring reaction rates. Finally, the researchers added
the same amount of peroxidase to each test tube and measured the rate of each
reaction at 23°C. The results of the experiment are represented in Figure 1.
One of the researchers proposes using oxygen gas production to measure reaction
rates. Which of the following statements best justifies the use of the proposed
modification as a way of creating an appropriate - ANSWER-The experiment can be
repeated without guaiacol, which will reveal the effect of guaiacol on the reaction
rates.
Aminolevulinate dehydratase (ALAD) is an enzyme that relies on zinc as a
coenzyme. A zinc ion binds to the ALAD active site, where it forms favorable
interactions with the side chains of three amino acids. Researchers have found that
substituting a lead ion for a zinc ion in the ALAD active site causes inhibition of
ALAD.
Which of the following statements best helps explain how the lead ion causes
inhibition of ALAD? - ANSWER-It changes the three-dimensional structure of the
active site so that ALAD is no longer compatible with its substrate.
Acetylcholinesterase (AChE) is a protein that catalyzes the conversion of
acetylcholine to acetate and choline. When the concentration of AChE in an aqueous
solution is held constant, the rate of the reaction catalyzed by AChE increases with
increasing concentrations of substrate. At low concentrations of acetylcholine, a
small increase in the substrate concentration results in a large increase in the
reaction rate. At high concentrations of acetylcholine, however, a large increase in
the substrate concentration results in only a small increase in the reaction rate.
Which of the following statements correctly explains the observed effect of the
acetylcholine concentration on the rate of the enzyme-catalyzed reaction? -
ANSWER-The active site of AChE is specific for acetylcholine, and only one
substrate molecule can occupy the active site at a time.
A researcher proposes a model to explain how enzyme-substrate interactions
determine enzyme specificity. The model is based on the idea that substrate
molecules form favorable interactions with the amino acid side chains in an enzyme's
active site.
Based on the model, which of the following statements best explains an enzyme's
specificity for a particular substrate molecule? - ANSWER-A molecule with negative
charges interacts with positively charged side chains in the enzyme's active site.
, Catalase is an enzyme found in yeast cells that facilitates the chemical breakdown of
hydrogen peroxide to water and oxygen gas. An experiment was conducted to
determine the effect of pH on catalase function. Five buffer solutions of varying pH
(2, 4, 6, 8, and 10) were prepared and added to separate test tubes. Hydrogen
peroxide (H2O2) was added to each test tube. Yeast was added, and the reactions
were timed. After 1 minute the amount of oxygen gas released was determined by
measuring the foam layer produced in each test tube. Figure 1 illustrates the
experimental setup.
A set of five additional test tubes were prepared and used as controls. Which of the
following best describes the contents expected to be contained in one of the five
control test tubes? - ANSWER-pH 4 buffer solution and hydrogen peroxide only
A student designs an experiment to investigate the influence of temperature on
enzyme function. The student's plan is presented in Table 1. Which test tubes are
controls in the experiment?
Test Tube Substrate Added Enzyme Added Temperature (°C)
1 Yes No 10
2 Yes Yes 10
3 Yes No 20
4 Yes Yes 20
5 Yes No 30
6 Yes Yes 30
7 Yes No 40
8 Yes Yes 40 - ANSWER-Test tubes 1, 3, 5, and 7
A researcher designs an experiment to investigate whether soil bacteria trigger the
synthesis of defense enzymes in plant roots. The design of the experiment is
presented in Table 1. For each group in the experiment, the researcher will
determine the average rate of change in the amount of defense enzymes in the roots
of the seedlings.
Group Number of Seedlings Type of Soil Treatment Solution
1 10 Sterile potting soil Contains actively reproducing soil bacteria
2 10 Sterile potting soil Contains heat-killed soil bacteria
3 10 Sterile potting soil Contains no soil bacteria
Which of the following statements best helps justify the inclusion of group 2 as one of
the controls in the experiment? - ANSWER-It will show whether the changes
observed in group 1 depend on the metabolic activity of soil bacteria.
Pectinase is a protein that catalyzes the breakdown of pectic polysaccharides in
plant cell walls. A researcher designs an experiment to investigate the effect of
salinity on the ability of pectinase to lower the activation energy of the reaction
involved. The design of the experiment is presented in Table 1. For each test tube,
the researcher will measure the amount of product formed over 20 minutes.
Test Tube Sodium Chloride Concentration (molar) Temperature (degrees C)
Substrate Added Pectinase Added
1 0 23 Yes No
2 0 23 Yes Yes
3 0.5 23 Yes No
4 0.5 23 Yes Yes
5 1.0 23 Yes No
