Question 1

Which is an example of an enzyme using substrate orientation as a mechanism for lowering the activation energy of a reaction?

Accepted Answer

A)  Aligning the substrate atoms so they are brought into proximity with each other, favoring the chemical reaction 
B)  Altering the hydrophobicity of a substrate (e.g., making a hydrophobic molecule hydrophilic) 
C)  Altering the shape of the enzyme to favor expulsion of the product 
D)  Aligning two different substrates such that their reactive atoms are held as far apart as possible 
E)  Chemically cleaving the substrate so that the small substrate fragments can enter solution more easily 
A)  Aligning the substrate atoms so they are brought into proximity with each other, favoring the chemical reaction 
B)  Altering the hydrophobicity of a substrate (e.g., making a hydrophobic molecule hydrophilic) 
C)  Altering the shape of the enzyme to favor expulsion of the product 
D)  Aligning two different substrates such that their reactive atoms are held as far apart as possible 
E)  Chemically cleaving the substrate so that the small substrate fragments can enter solution more easily

Question 2

Which series best summarizes the relative energies of the different stages of an endergonic chemical reaction?

Accepted Answer

A)  Products > transition state > reactants 
B)  Reactants > transition state > products 
C)  Transition state > reactants > products 
D)  Transition state > products > reactants 
E)  Reactants > products > transition state 
A)  Products > transition state > reactants 
B)  Reactants > transition state > products 
C)  Transition state > reactants > products 
D)  Transition state > products > reactants 
E)  Reactants > products > transition state

Question 3

What is the order in which the following molecules would be produced if phosphate ions were removed from ATP one at a time?

Accepted Answer

A)  ATP, ADP, AMP, adenosine 
B)  AMP, ADP, ATP, adenosine 
C)  Adenosine, ATP, AMP, ADP 
D)  ATP, AMP, ADP, adenosine 
E)  ADP, adenosine, AMP, ATP 
A)  ATP, ADP, AMP, adenosine 
B)  AMP, ADP, ATP, adenosine 
C)  Adenosine, ATP, AMP, ADP 
D)  ATP, AMP, ADP, adenosine 
E)  ADP, adenosine, AMP, ATP

Question 4

Which of the following could we infer about a chemical reaction with a large positive change in entropy (F1F1F1S1F1F1F10S) as the reaction proceeds and no corresponding change in enthalpy (F1F1F1S1F1F1F10H)?

Accepted Answer

A)  Total F1F1F1S1F1F1F10G of the reaction will decrease. 
B)  The disorder of the system will decrease. 
C)  The temperature at which the reaction occurs will change. 
D)  The reaction is anabolic in nature. 
E)  The reaction is highly complex. 
A)  Total F1F1F1S1F1F1F10G of the reaction will decrease. 
B)  The disorder of the system will decrease. 
C)  The temperature at which the reaction occurs will change. 
D)  The reaction is anabolic in nature. 
E)  The reaction is highly complex.

Question 5

Refer to the figure below.   This graph shows the change in free energy for the same reaction with and without a catalyst.Which tracing represents the catalyzed reaction and why?

Accepted Answer

A)  The blue tracing represents the catalyzed reaction because it has a larger F1F1F1S1F1F1F10G than the uncatalyzed reaction. 
B)  The blue tracing represents the catalyzed reaction because it has a larger activation energy than the uncatalyzed reaction. 
C)  The red tracing represents the catalyzed reaction because it has a smaller F1F1F1S1F1F1F10G than the uncatalyzed reaction. 
D)  The red tracing represents the catalyzed reaction because it has a smaller activation energy than the uncatalyzed reaction. 
E)  The red tracing represents the catalyzed reaction because it leads to the formation of more products than the uncatalyzed reaction. 
A)  The blue tracing represents the catalyzed reaction because it has a larger F1F1F1S1F1F1F10G than the uncatalyzed reaction. 
B)  The blue tracing represents the catalyzed reaction because it has a larger activation energy than the uncatalyzed reaction. 
C)  The red tracing represents the catalyzed reaction because it has a smaller F1F1F1S1F1F1F10G than the uncatalyzed reaction. 
D)  The red tracing represents the catalyzed reaction because it has a smaller activation energy than the uncatalyzed reaction. 
E)  The red tracing represents the catalyzed reaction because it leads to the formation of more products than the uncatalyzed reaction.

Question 6

In which sequence does the form of energy change as a person sees a friend and waves hello?

Accepted Answer

A)  Light F1F1F1S1F1F1F10 electrical F1F1F1S1F1F1F10 mechanical F1F1F1S1F1F1F10 chemical 
B)  Mechanical F1F1F1S1F1F1F10 electrical F1F1F1S1F1F1F10 chemical F1F1F1S1F1F1F10 light 
C)  Light F1F1F1S1F1F1F10 chemical F1F1F1S1F1F1F10 electrical F1F1F1S1F1F1F10 mechanical 
D)  Light F1F1F1S1F1F1F10 mechanical F1F1F1S1F1F1F10 chemical F1F1F1S1F1F1F10 electrical 
E)  Electrical F1F1F1S1F1F1F10 mechanical F1F1F1S1F1F1F10 light F1F1F1S1F1F1F10 chemical 
A)  Light F1F1F1S1F1F1F10 electrical F1F1F1S1F1F1F10 mechanical F1F1F1S1F1F1F10 chemical 
B)  Mechanical F1F1F1S1F1F1F10 electrical F1F1F1S1F1F1F10 chemical F1F1F1S1F1F1F10 light 
C)  Light F1F1F1S1F1F1F10 chemical F1F1F1S1F1F1F10 electrical F1F1F1S1F1F1F10 mechanical 
D)  Light F1F1F1S1F1F1F10 mechanical F1F1F1S1F1F1F10 chemical F1F1F1S1F1F1F10 electrical 
E)  Electrical F1F1F1S1F1F1F10 mechanical F1F1F1S1F1F1F10 light F1F1F1S1F1F1F10 chemical

Question 7

Refer to the table below.   The hydrolysis of one mole of ATP to ADP and inorganic phosphate is accompanied by the release of 7.3 kcal of energy.Some biological transformations are coupled to ATP hydrolysis.Reaction _______ is an example of a biological transformation that could be coupled to ATP hydrolysis.

Accepted Answer

The answer of Refer to the table below.  ...

Question 8

How do competitive and noncompetitive enzyme inhibitors differ from each other?

Accepted Answer

A)  Competitive inhibitors bind to the active site, whereas noncompetitive inhibitors change the shape of the active site. 
B)  Competitive inhibitors have a higher energy of activation than noncompetitive inhibitors have. 
C)  Noncompetitive enzyme inhibitors contain magnesium, whereas competitive inhibitors contain iron. 
D)  Noncompetitive enzyme inhibitors are reversible, whereas competitive inhibitors are irreversible. 
E)  They function at different pH values. 
A)  Competitive inhibitors bind to the active site, whereas noncompetitive inhibitors change the shape of the active site. 
B)  Competitive inhibitors have a higher energy of activation than noncompetitive inhibitors have. 
C)  Noncompetitive enzyme inhibitors contain magnesium, whereas competitive inhibitors contain iron. 
D)  Noncompetitive enzyme inhibitors are reversible, whereas competitive inhibitors are irreversible. 
E)  They function at different pH values.

Question 9

The addition of the competitive inhibitor mevinolin slows the reaction HMG-CoA F1F1F1S1F1F1F10 mevalonate, which is catalyzed by the enzyme HMG-CoA reductase.In order to overcome the effects of mevinolin and increase the rate of the reaction, you would

Accepted Answer

A)  add more mevalonate. 
B)  add more HMG-CoA. 
C)  lower the temperature of the reaction. 
D)  add a prosthetic group. 
E)  lower the rate constant of the reaction. 
A)  add more mevalonate. 
B)  add more HMG-CoA. 
C)  lower the temperature of the reaction. 
D)  add a prosthetic group. 
E)  lower the rate constant of the reaction.

Question 10

The phosphorylation of glucose to glucose 6-phosphate has a F1F1F1S1F1F1F10G of +4.0 kcal/mol.If hexokinase is added to speed up the rate of this reaction, the F1F1F1S1F1F1F10G will

Accepted Answer

A)  increase. 
B)  decrease. 
C)  stay the same. 
D)  increase, but only with an increase in enzyme amount. 
E)  decrease, but only with a decrease in enzyme amount. 
A)  increase. 
B)  decrease. 
C)  stay the same. 
D)  increase, but only with an increase in enzyme amount. 
E)  decrease, but only with a decrease in enzyme amount.

Question 11

Refer to the graph below.   Ten sequential reactions take place in cells during glycolysis.The graph shows the relative free energies of each chemical intermediate relative to glucose, the starting reactant in glycolysis.Based on the information shown in the graph, reactions numbered _______ are all possibilities for reactions that might be coupled to the reaction in which ATP is hydrolyzed.

Accepted Answer

2, 4, 5, 6

Question 12

You make a solution of glucose 1-phosphate and allow it to isomerize to form glucose 6-phosphate.Eventually, you have an equilibrium mixture of the two isomers.What can you do to increase the concentration of glucose 6-phosphate in the solution?

Accepted Answer

A)  Add more glucose. 
B)  Add more phosphate. 
C)  Add a higher concentration of reactant and allow it to make more product. 
D)  Add ATP as an energy source for the forward reaction (F1F1F1S1F1F1F10G = ‒7.1 kJ/mol) to make more product. 
E)  Add an enzyme to lower the ΔG of the reaction so more product is made. 
A)  Add more glucose. 
B)  Add more phosphate. 
C)  Add a higher concentration of reactant and allow it to make more product. 
D)  Add ATP as an energy source for the forward reaction (F1F1F1S1F1F1F10G = ‒7.1 kJ/mol) to make more product. 
E)  Add an enzyme to lower the ΔG of the reaction so more product is made.

Question 13

Refer to the figure below, which shows the reaction between fumarate and water to produce malate.   Fumarase is the enzyme that catalyzes this reaction in cells.Which statement can be used as evidence that orientation of reactant molecules is part of the function of fumarase as a catalyst?

Accepted Answer

A)  Fumarase uses no coenzyme but requires one Fe2+ ion at its active site. 
B)  Fumarase catalyzes both the forward and reverse reactions between fumarate and malate. 
C)  Fumarase binds one fumarate molecule and one water molecule the same way for every reaction. 
D)  The active site of fumarase contains a histidine and a lysine that function as an acid and a base, respectively, during catalysis. 
E)  Mutation of the active site lysine to other amino acids obliterates or severely reduces activity in fumarase. 
A)  Fumarase uses no coenzyme but requires one Fe2+ ion at its active site. 
B)  Fumarase catalyzes both the forward and reverse reactions between fumarate and malate. 
C)  Fumarase binds one fumarate molecule and one water molecule the same way for every reaction. 
D)  The active site of fumarase contains a histidine and a lysine that function as an acid and a base, respectively, during catalysis. 
E)  Mutation of the active site lysine to other amino acids obliterates or severely reduces activity in fumarase.

Question 14

Some kinases can affect the activity of an enzyme by the addition of phosphate groups, which can then be removed, much like an "on/off" switch.These modifications are an example of

Accepted Answer

A)  feedback inhibition. 
B)  phosphatase activity. 
C)  reversible phosphorylation. 
D)  noncovalent regulation. 
E)  allosteric regulation. 
A)  feedback inhibition. 
B)  phosphatase activity. 
C)  reversible phosphorylation. 
D)  noncovalent regulation. 
E)  allosteric regulation.

Question 15

Suppose that, in a closed system, there is an input of energy as 1 kJ of light.The light energy is converted to glucose, then ATP, and finally to mechanical energy.Which statement about the amount of mechanical energy available is true?

Accepted Answer

A)  There is 1 kJ of mechanical energy available to do work. 
B)  The amount of usable energy decreases with each conversion, so less than 1 kJ of energy is available for mechanical work. 
C)  All of the reactions involved are anabolic, so there is 0.25 kJ of mechanical energy available. 
D)  All of the reactions involved are exergonic, so the number of kilojoules of mechanical energy produced is greater than the 1 kJ input. 
E)  All of the reactions involved are endergonic, so without constant input of energy, no mechanical energy is produced. 
A)  There is 1 kJ of mechanical energy available to do work. 
B)  The amount of usable energy decreases with each conversion, so less than 1 kJ of energy is available for mechanical work. 
C)  All of the reactions involved are anabolic, so there is 0.25 kJ of mechanical energy available. 
D)  All of the reactions involved are exergonic, so the number of kilojoules of mechanical energy produced is greater than the 1 kJ input. 
E)  All of the reactions involved are endergonic, so without constant input of energy, no mechanical energy is produced.

Question 16

When an enzyme is heated until its three-dimensional structure is destroyed, the enzyme is said to be _______.

Accepted Answer

The answer of When an enzyme is heated until its...

Question 17

Where is the chemical energy that is used to drive endergonic reactions contained in a molecule of ATP?

Accepted Answer

A)  The 3ʹ -OH bond of the ribose sugar 
B)  The P-O bond of the third phosphate group 
C)  In the N-C bonds of the adenine base group 
D)  In hydrogen bonds with another ATP molecule 
E)  In solution with H2O 
A)  The 3ʹ -OH bond of the ribose sugar 
B)  The P-O bond of the third phosphate group 
C)  In the N-C bonds of the adenine base group 
D)  In hydrogen bonds with another ATP molecule 
E)  In solution with H2O

Question 18

The synthesis of the enzyme lipase would be classified as anabolic because

Accepted Answer

A)  the resulting enzyme can catalyze the breakdown of lipids for energy. 
B)  energy is captured in the peptide bonds between the amino acids that compose lipase. 
C)  synthesis of lipase increases entropy as compared with the free amino acids. 
D)  an increase in temperature is required to make the enzyme. 
E)  free amino acids have greater free energy than the lipase enzyme. 
A)  the resulting enzyme can catalyze the breakdown of lipids for energy. 
B)  energy is captured in the peptide bonds between the amino acids that compose lipase. 
C)  synthesis of lipase increases entropy as compared with the free amino acids. 
D)  an increase in temperature is required to make the enzyme. 
E)  free amino acids have greater free energy than the lipase enzyme.

Question 19

Which statement regarding ATP is not true?

Accepted Answer

A)  The average person produces about 40 kg of ATP per day. 
B)  The average person hydrolyzes about 40 kg of ATP per day. 
C)  ATP is readily hydrolyzed in water. 
D)  ATP is chemically stable and can be stored easily for extensive periods of time. 
E)  ATP can be moved around the cell for its optimal use at a different location. 
A)  The average person produces about 40 kg of ATP per day. 
B)  The average person hydrolyzes about 40 kg of ATP per day. 
C)  ATP is readily hydrolyzed in water. 
D)  ATP is chemically stable and can be stored easily for extensive periods of time. 
E)  ATP can be moved around the cell for its optimal use at a different location.

Question 20

Refer to the table below.   The enzyme alcohol dehydrogenase was purified from yeast cells.It was then dialyzed against a buffer solution, which means that it was placed inside a bag consisting of a semipermeable membrane that allowed small molecules and ions to pass through, but not the enzyme.The enzyme was removed from the dialysis bag, incubated with the compound N-ethylmaleimide, and then dialyzed a second time.At each step, the enzyme's catalytic activity was measured and expressed as a percentage of its original activity shown in the table.Which statement expresses a valid conclusion that can be made based on these results?

Accepted Answer

A)  N-ethylmaleimide is a competitive inhibitor of alcohol dehydrogenase. 
B)  N-ethylmaleimide is a reversible inhibitor of alcohol dehydrogenase. 
C)  N-ethylmaleimide is an activator of alcohol dehydrogenase. 
D)  N-ethylmaleimide is a noncompetitive inhibitor of alcohol dehydrogenase. 
E)  N-ethylmaleimide is an irreversible inhibitor of alcohol dehydrogenase. 
A)  N-ethylmaleimide is a competitive inhibitor of alcohol dehydrogenase. 
B)  N-ethylmaleimide is a reversible inhibitor of alcohol dehydrogenase. 
C)  N-ethylmaleimide is an activator of alcohol dehydrogenase. 
D)  N-ethylmaleimide is a noncompetitive inhibitor of alcohol dehydrogenase. 
E)  N-ethylmaleimide is an irreversible inhibitor of alcohol dehydrogenase.

Exam 8: Energy, Enzymes, and Metabolism

Which is an example of an enzyme using substrate orientation as a mechanism for lowering the activation energy of a reaction?

Which series best summarizes the relative energies of the different stages of an endergonic chemical reaction?

What is the order in which the following molecules would be produced if phosphate ions were removed from ATP one at a time?

Which of the following could we infer about a chemical reaction with a large positive change in entropy (S) as the reaction proceeds and no corresponding change in enthalpy (H)?

Refer to the figure below. This graph shows the change in free energy for the same reaction with and without a catalyst.Which tracing represents the catalyzed reaction and why?

In which sequence does the form of energy change as a person sees a friend and waves hello?

How do competitive and noncompetitive enzyme inhibitors differ from each other?

The addition of the competitive inhibitor mevinolin slows the reaction HMG-CoA  mevalonate, which is catalyzed by the enzyme HMG-CoA reductase.In order to overcome the effects of mevinolin and increase the rate of the reaction, you would

The phosphorylation of glucose to glucose 6-phosphate has a G of +4.0 kcal/mol.If hexokinase is added to speed up the rate of this reaction, the G will

You make a solution of glucose 1-phosphate and allow it to isomerize to form glucose 6-phosphate.Eventually, you have an equilibrium mixture of the two isomers.What can you do to increase the concentration of glucose 6-phosphate in the solution?

Refer to the figure below, which shows the reaction between fumarate and water to produce malate. Fumarase is the enzyme that catalyzes this reaction in cells.Which statement can be used as evidence that orientation of reactant molecules is part of the function of fumarase as a catalyst?

Some kinases can affect the activity of an enzyme by the addition of phosphate groups, which can then be removed, much like an "on/off" switch.These modifications are an example of

Suppose that, in a closed system, there is an input of energy as 1 kJ of light.The light energy is converted to glucose, then ATP, and finally to mechanical energy.Which statement about the amount of mechanical energy available is true?

When an enzyme is heated until its three-dimensional structure is destroyed, the enzyme is said to be _______.

Where is the chemical energy that is used to drive endergonic reactions contained in a molecule of ATP?

The synthesis of the enzyme lipase would be classified as anabolic because

Which statement regarding ATP is not true?

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