ap bio quiz 3.1-3.3 cellular energetics
(enzymes)questions and 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?
A
The enzyme's active site binds to and stabilizes the reactant, which decreases the free-
energy change of the reaction.
B
The enzyme's active site binds to and stabilizes the transition state, which decreases
the activation energy of the reaction.
C
The enzyme's active site binds to and stabilizes the product, which increases the
amount of energy released by the reaction.
D
The enzyme's active site binds to and stabilizes both the reactant and the product at the
same time, which increases the reaction's equilibrium constant. ANSWERS B
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?
A
The free energy of the reactants is greater than the free energy of the products.
B
The equilibrium constant of the reaction is much greater than 1.
C
The shape and charge of the substrates are compatible with the active site of the
enzyme.
D
The concentration of the enzyme inside living cells is greater than the concentration of
substrate. ANSWERS C
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?
A
Both glucose and water are polar molecules that form favorable interactions with
charged and polar amino acid side chains in hexokinase's active site.
B
Both glucose and water have oxygen atoms that can form covalent bonds with the
phosphorus atoms of phosphate groups.
C
Glucose is an energy-rich organic molecule that can be broken down by glycolysis to
produce ATP, whereas w ANSWERS D
Glucose has the right shape and charge to cause hexokinase to undergo a structural
change needed for catalysis, whereas water does not.
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?
A
It will provide a measurement of amylase activity at an acidic pH.
B
It will provide a measurement of amylase activity at a basic pH.
C
It will show the color change that occurs in the absenc ANSWERS C
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
(enzymes)questions and 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?
A
The enzyme's active site binds to and stabilizes the reactant, which decreases the free-
energy change of the reaction.
B
The enzyme's active site binds to and stabilizes the transition state, which decreases
the activation energy of the reaction.
C
The enzyme's active site binds to and stabilizes the product, which increases the
amount of energy released by the reaction.
D
The enzyme's active site binds to and stabilizes both the reactant and the product at the
same time, which increases the reaction's equilibrium constant. ANSWERS B
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?
A
The free energy of the reactants is greater than the free energy of the products.
B
The equilibrium constant of the reaction is much greater than 1.
C
The shape and charge of the substrates are compatible with the active site of the
enzyme.
D
The concentration of the enzyme inside living cells is greater than the concentration of
substrate. ANSWERS C
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?
A
Both glucose and water are polar molecules that form favorable interactions with
charged and polar amino acid side chains in hexokinase's active site.
B
Both glucose and water have oxygen atoms that can form covalent bonds with the
phosphorus atoms of phosphate groups.
C
Glucose is an energy-rich organic molecule that can be broken down by glycolysis to
produce ATP, whereas w ANSWERS D
Glucose has the right shape and charge to cause hexokinase to undergo a structural
change needed for catalysis, whereas water does not.
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?
A
It will provide a measurement of amylase activity at an acidic pH.
B
It will provide a measurement of amylase activity at a basic pH.
C
It will show the color change that occurs in the absenc ANSWERS C
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
