AP Biology. Unit 3 Practice UPDATED
ACTUAL Exam Questions and CORRECT
Answers
A researcher proposes a model of an enzyme-catalyzed reaction in which a reactant is converted
to a product. The model is based on the idea that the reactant passes through a transition state
within the enzyme-substrate complex before the reactant is converted to the product.
Which of the following statements best helps explain how the enzyme speeds up the reaction? -
CORRECT ANSWER - The enzyme's active site binds to and stabilizes the transition state,
which decreases the activation energy of the reaction.
Which of the following statements best helps explain the reaction specificity of an enzyme? -
CORRECT ANSWER - The shape and charge of the substrates are compatible with the active
site of the enzyme.
The enzyme hexokinase catalyzes the conversion of glucose to glucose-6-phosphate, which is an
important step in glycolysis. The reaction involves the transfer of a phosphate group from ATP to
glucose.
Either a glucose molecule or a water molecule can fit in the active site of hexokinase. The
presence of a water molecule in hexokinase's active site would result in the hydrolysis of ATP to
ADP instead of the conversion of glucose to glucose-6-phosphate.
Which of the following statements best helps explain the reaction specificity of hexokinase? -
CORRECT ANSWER - Glucose has the right shape and charge to cause hexokinase to
undergo a structural change needed for catalysis, whereas water does not.
Alcohol dehydrogenase (ADH) is an enzyme that aids in the decomposition of ethyl alcohol
(C2H5OH) into nontoxic substances. Methyl alcohol acts as a competitive inhibitor of ethyl
alcohol by competing for the same active site on ADH. When attached to ADH, methyl alcohol is
converted to formaldehyde, which is toxic in the body.
Which of the following statements best predicts the effect of increasing the concentration of
substrate (ethyl alcohol), while keeping the concentration of the inhibitor (methyl alcohol)
constant? - CORRECT ANSWER - Competitive inhibition will decrease because the
proportion of the active sites occupied by substrate will increase.
, Amylase is a protein that catalyzes the conversion of starch to simple sugars. Amylase activity in
an aqueous solution can be measured by using iodine as a starch indicator. A solution containing
iodine and starch will have a dark-blue color, whereas a solution containing iodine but no starch
will have a light-brown color. The color change of an iodine solution from dark blue to light
brown can be used to measure the rate at which starch is converted to simple sugars.
A student designs an experiment to investigate the effect of environmental pH on amylase
function. The design of the experiment is presented in Table 1.
Which of the following statements best justifies the inclusion of test tube V as a control in the
experiment? - CORRECT ANSWER - It will show the color change that occurs in the absence
of enzyme activity.
A researcher claims that some bacteria contain factors that influence the function of a particular
enzyme but other bacteria do not. To test the claim experimentally, the researcher will grow two
different bacterial strains in separate liquid cultures and isolate the contents of the cells in each
culture. The researcher will add different combinations of cellular contents, substrate, and
enzyme to test tubes containing a buffer solution adjusted to the optimal pH of the enzyme and
then measure the rate of product formation. The design of the researcher's experiment is
presented in Table 1.
Which of the following statements best justifies the inclusion of test tubes 3 and 7 in the
experiment? - CORRECT ANSWER - They will show whether the isolated cellular contents
have enzymatic activity.
Butterflies of the genus Colias live in the Rocky Mountains, where they experience a wide range
of temperatures. Different variants of a particular glycolytic enzyme in the flight muscles are
optimally active at different temperatures. Within the same population, some individual
butterflies fly most effectively at 29°C , while others fly most effectively at 40°C. Still others can
be equally active at both temperatures. Which of the following claims is most consistent with the
observed butterfly behavior? - CORRECT ANSWER - Butterflies that express two variants of
the enzyme are active over a greater range of temperature.
A researcher designs an experiment to investigate the effect of environmental temperature on the
function of an enzyme. For each trial included in the experiment, the researcher will add the
enzyme and its substrate to an aqueous buffer solution and then measure the amount of product
formed over 20 minutes.
Which of the following must remain the same for all trials of this experiment? - CORRECT
ANSWER - The initial concentration of the substrate
ACTUAL Exam Questions and CORRECT
Answers
A researcher proposes a model of an enzyme-catalyzed reaction in which a reactant is converted
to a product. The model is based on the idea that the reactant passes through a transition state
within the enzyme-substrate complex before the reactant is converted to the product.
Which of the following statements best helps explain how the enzyme speeds up the reaction? -
CORRECT ANSWER - The enzyme's active site binds to and stabilizes the transition state,
which decreases the activation energy of the reaction.
Which of the following statements best helps explain the reaction specificity of an enzyme? -
CORRECT ANSWER - The shape and charge of the substrates are compatible with the active
site of the enzyme.
The enzyme hexokinase catalyzes the conversion of glucose to glucose-6-phosphate, which is an
important step in glycolysis. The reaction involves the transfer of a phosphate group from ATP to
glucose.
Either a glucose molecule or a water molecule can fit in the active site of hexokinase. The
presence of a water molecule in hexokinase's active site would result in the hydrolysis of ATP to
ADP instead of the conversion of glucose to glucose-6-phosphate.
Which of the following statements best helps explain the reaction specificity of hexokinase? -
CORRECT ANSWER - Glucose has the right shape and charge to cause hexokinase to
undergo a structural change needed for catalysis, whereas water does not.
Alcohol dehydrogenase (ADH) is an enzyme that aids in the decomposition of ethyl alcohol
(C2H5OH) into nontoxic substances. Methyl alcohol acts as a competitive inhibitor of ethyl
alcohol by competing for the same active site on ADH. When attached to ADH, methyl alcohol is
converted to formaldehyde, which is toxic in the body.
Which of the following statements best predicts the effect of increasing the concentration of
substrate (ethyl alcohol), while keeping the concentration of the inhibitor (methyl alcohol)
constant? - CORRECT ANSWER - Competitive inhibition will decrease because the
proportion of the active sites occupied by substrate will increase.
, Amylase is a protein that catalyzes the conversion of starch to simple sugars. Amylase activity in
an aqueous solution can be measured by using iodine as a starch indicator. A solution containing
iodine and starch will have a dark-blue color, whereas a solution containing iodine but no starch
will have a light-brown color. The color change of an iodine solution from dark blue to light
brown can be used to measure the rate at which starch is converted to simple sugars.
A student designs an experiment to investigate the effect of environmental pH on amylase
function. The design of the experiment is presented in Table 1.
Which of the following statements best justifies the inclusion of test tube V as a control in the
experiment? - CORRECT ANSWER - It will show the color change that occurs in the absence
of enzyme activity.
A researcher claims that some bacteria contain factors that influence the function of a particular
enzyme but other bacteria do not. To test the claim experimentally, the researcher will grow two
different bacterial strains in separate liquid cultures and isolate the contents of the cells in each
culture. The researcher will add different combinations of cellular contents, substrate, and
enzyme to test tubes containing a buffer solution adjusted to the optimal pH of the enzyme and
then measure the rate of product formation. The design of the researcher's experiment is
presented in Table 1.
Which of the following statements best justifies the inclusion of test tubes 3 and 7 in the
experiment? - CORRECT ANSWER - They will show whether the isolated cellular contents
have enzymatic activity.
Butterflies of the genus Colias live in the Rocky Mountains, where they experience a wide range
of temperatures. Different variants of a particular glycolytic enzyme in the flight muscles are
optimally active at different temperatures. Within the same population, some individual
butterflies fly most effectively at 29°C , while others fly most effectively at 40°C. Still others can
be equally active at both temperatures. Which of the following claims is most consistent with the
observed butterfly behavior? - CORRECT ANSWER - Butterflies that express two variants of
the enzyme are active over a greater range of temperature.
A researcher designs an experiment to investigate the effect of environmental temperature on the
function of an enzyme. For each trial included in the experiment, the researcher will add the
enzyme and its substrate to an aqueous buffer solution and then measure the amount of product
formed over 20 minutes.
Which of the following must remain the same for all trials of this experiment? - CORRECT
ANSWER - The initial concentration of the substrate
