Question 1

If an enzyme is added to a solution where its substrate and product are in equilibrium, what will occur?

Accepted Answer

A)  Additional product will be formed. 
B)  Additional substrate will be formed. 
C)  The reaction will change from endergonic to exergonic. 
D)  The free energy of the system will change. 
E)  Nothing; the reaction will stay at equilibrium 
A)  Additional product will be formed. 
B)  Additional substrate will be formed. 
C)  The reaction will change from endergonic to exergonic. 
D)  The free energy of the system will change. 
E)  Nothing; the reaction will stay at equilibrium

Question 2

Which of the following is an example of potential rather than kinetic energy?

Accepted Answer

A)  the muscle contractions of a person mowing grass 
B)  water rushing over Niagara Falls 
C)  light flashes emitted by a firefly 
D)  a molecule of glucose 
E)  the flight of an insect foraging for food 
A)  the muscle contractions of a person mowing grass 
B)  water rushing over Niagara Falls 
C)  light flashes emitted by a firefly 
D)  a molecule of glucose 
E)  the flight of an insect foraging for food

Question 3

In experimental tests of enzyme evolution, where a gene encoding an enzyme is subjected to multiple cycles of random mutagenesis and selection for altered substrate specificity, the resulting enzyme had multiple amino acid changes associated with altered substrate specificity. Where in the enzyme were these amino acid changes located?

Accepted Answer

A)  only in the active site 
B)  only in the active site or near the active site 
C)  in or near the active site and at surface sites away from the active site 
D)  only at surface sites away from the active site 
E)  only in the hydrophobic interior of the folded protein 
A)  only in the active site 
B)  only in the active site or near the active site 
C)  in or near the active site and at surface sites away from the active site 
D)  only at surface sites away from the active site 
E)  only in the hydrophobic interior of the folded protein

Question 4

Protein kinases are enzymes that transfer the terminal phosphate from ATP to an amino acid residue on the target protein. Many are located on the plasma membrane as integral membrane proteins or peripheral membrane proteins. What purpose may be served by their plasma membrane localization?

Accepted Answer

A)  ATP is more abundant near the plasma membrane. 
B)  They can more readily encounter and phosphorylate other membrane proteins. 
C)  Membrane localization lowers the activation energy of the phosphorylation reaction. 
D)  They flip back and forth across the membrane to access target proteins on either side. 
E)  They require phospholipids as a cofactor. 
A)  ATP is more abundant near the plasma membrane. 
B)  They can more readily encounter and phosphorylate other membrane proteins. 
C)  Membrane localization lowers the activation energy of the phosphorylation reaction. 
D)  They flip back and forth across the membrane to access target proteins on either side. 
E)  They require phospholipids as a cofactor.

Question 5

During a laboratory experiment, you discover that an enzyme-catalyzed reaction has a ∆G of -20 kcal/mol. If you double the amount of enzyme in the reaction, what will be the ∆G for the new reaction?

Accepted Answer

A)  -40 kcal/mol 
B)  -20 kcal/mol 
C)  0 kcal/mol 
D)  +20 kcal/mol 
E)  +40 kcal/mol 
A)  -40 kcal/mol 
B)  -20 kcal/mol 
C)  0 kcal/mol 
D)  +20 kcal/mol 
E)  +40 kcal/mol

Question 6

Which of the following is a statement of the first law of thermodynamics?

Accepted Answer

A)  Energy cannot be created or destroyed. 
B)  The entropy of the universe is decreasing. 
C)  The entropy of the universe is constant. 
D)  Kinetic energy is stored energy that results from the specific arrangement of matter. 
E)  Energy cannot be transferred or transformed. 
A)  Energy cannot be created or destroyed. 
B)  The entropy of the universe is decreasing. 
C)  The entropy of the universe is constant. 
D)  Kinetic energy is stored energy that results from the specific arrangement of matter. 
E)  Energy cannot be transferred or transformed.

Question 7

Succinate dehydrogenase catalyzes the conversion of succinate to fumarate. The reaction is inhibited by malonic acid, which resembles succinate but cannot be acted upon by succinate dehydrogenase. Increasing the ratio of succinate to malonic acid reduces the inhibitory effect of malonic acid.
-What is malonic acid's role with respect to succinate dehydrogenase?

Accepted Answer

A)  It is a competitive inhibitor. 
B)  It blocks the binding of fumarate. 
C)  It is a noncompetitive inhibitor. 
D)  It is able to bind to succinate. 
E)  It is an allosteric regulator. 
A)  It is a competitive inhibitor. 
B)  It blocks the binding of fumarate. 
C)  It is a noncompetitive inhibitor. 
D)  It is able to bind to succinate. 
E)  It is an allosteric regulator.

Question 8

Which of the following statements is true about enzyme-catalyzed reactions?

Accepted Answer

A)  The reaction is faster than the same reaction in the absence of the enzyme. 
B)  The free-energy change of the reaction is opposite from the reaction that occurs in the absence of the enzyme. 
C)  The reaction always goes in the direction toward chemical equilibrium. 
D)  Enzyme-catalyzed reactions require energy to activate the enzyme. 
E)  Enzyme-catalyzed reactions release more free energy than noncatalyzed reactions. 
A)  The reaction is faster than the same reaction in the absence of the enzyme. 
B)  The free-energy change of the reaction is opposite from the reaction that occurs in the absence of the enzyme. 
C)  The reaction always goes in the direction toward chemical equilibrium. 
D)  Enzyme-catalyzed reactions require energy to activate the enzyme. 
E)  Enzyme-catalyzed reactions release more free energy than noncatalyzed reactions.

Question 9

The mechanism in which the end product of a metabolic pathway inhibits an earlier step in the pathway is most precisely described as

Accepted Answer

A)  metabolic inhibition. 
B)  feedback inhibition. 
C)  allosteric inhibition. 
D)  noncooperative inhibition. 
E)  reversible inhibition. 
A)  metabolic inhibition. 
B)  feedback inhibition. 
C)  allosteric inhibition. 
D)  noncooperative inhibition. 
E)  reversible inhibition.

Question 10

Which of the following metabolic processes can occur without a net influx of energy from some other process?

Accepted Answer

A)  ADP + ℗i → ATP + H2O 
B)  C6H12O6 + 6 O2 → 6 CO2 + 6 H2O 
C)  6 CO2 + 6 H2O → C6H12O6 + 6 O2 
D)  amino acids → protein 
E)  glucose + fructose → sucrose 
A)  ADP + ℗i → ATP + H2O 
B)  C6H12O6 + 6 O2 → 6 CO2 + 6 H2O 
C)  6 CO2 + 6 H2O → C6H12O6 + 6 O2 
D)  amino acids → protein 
E)  glucose + fructose → sucrose

Question 11

Chemical equilibrium is relatively rare in living cells. Which of the following could be an example of a reaction at chemical equilibrium in a cell?

Accepted Answer

A)  a reaction in which the free energy at equilibrium is higher than the energy content at any point away from equilibrium 
B)  a chemical reaction in which the entropy change in the reaction is just balanced by an opposite entropy change in the cell's surroundings 
C)  an endergonic reaction in an active metabolic pathway where the energy for that reaction is supplied only by heat from the environment 
D)  a chemical reaction in which both the reactants and products are not being produced or used in any active metabolic pathway at that time in the cell 
E)  no possibility of having chemical equilibrium in any living cell 
A)  a reaction in which the free energy at equilibrium is higher than the energy content at any point away from equilibrium 
B)  a chemical reaction in which the entropy change in the reaction is just balanced by an opposite entropy change in the cell's surroundings 
C)  an endergonic reaction in an active metabolic pathway where the energy for that reaction is supplied only by heat from the environment 
D)  a chemical reaction in which both the reactants and products are not being produced or used in any active metabolic pathway at that time in the cell 
E)  no possibility of having chemical equilibrium in any living cell

Question 12

A chemical reaction that has a positive ΔG is best described as

Accepted Answer

A)  endergonic. 
B)  entropic 
C)  enthalpic. 
D)  spontaneous. 
E)  exergonic. 
A)  endergonic. 
B)  entropic 
C)  enthalpic. 
D)  spontaneous. 
E)  exergonic.

Question 13

Figure 6.1
-How do cells use the ATP cycle shown in Figure 6.1?

Accepted Answer

A)  Cells use the cycle to recycle ADP and phosphate. 
B)  Cells use the cycle to recycle energy released by ATP hydrolysis. 
C)  Cells use the cycle to recycle ADP, phosphate, and the energy released by ATP hydrolysis. 
D)  Cells use the cycle to generate or consume water molecules as needed. 
E)  Cells use the cycle primarily to generate heat. 
A)  Cells use the cycle to recycle ADP and phosphate. 
B)  Cells use the cycle to recycle energy released by ATP hydrolysis. 
C)  Cells use the cycle to recycle ADP, phosphate, and the energy released by ATP hydrolysis. 
D)  Cells use the cycle to generate or consume water molecules as needed. 
E)  Cells use the cycle primarily to generate heat.

Question 14

Which of the following statements is representative of the second law of thermodynamics?

Accepted Answer

A)  Conversion of energy from one form to another is always accompanied by some gain of free energy. 
B)  Heat represents a form of energy that can be used by most organisms to do work. 
C)  Without an input of energy, organisms would tend toward decreasing entropy. 
D)  Cells require a constant input of energy to maintain their high level of organization. 
E)  Every energy transformation by a cell decreases the entropy of the universe. 
A)  Conversion of energy from one form to another is always accompanied by some gain of free energy. 
B)  Heat represents a form of energy that can be used by most organisms to do work. 
C)  Without an input of energy, organisms would tend toward decreasing entropy. 
D)  Cells require a constant input of energy to maintain their high level of organization. 
E)  Every energy transformation by a cell decreases the entropy of the universe.

Question 15

Besides turning enzymes on or off, what other means does a cell use to control enzymatic activity?

Accepted Answer

A)  cessation of cellular protein synthesis 
B)  localization of enzymes into specific organelles or membranes 
C)  exporting enzymes out of the cell 
D)  connecting enzymes into large aggregates 
E)  hydrophobic interactions 
A)  cessation of cellular protein synthesis 
B)  localization of enzymes into specific organelles or membranes 
C)  exporting enzymes out of the cell 
D)  connecting enzymes into large aggregates 
E)  hydrophobic interactions

Question 16

Allosteric enzyme regulation is usually associated with

Accepted Answer

A)  lack of cooperativity. 
B)  feedback inhibition. 
C)  activating activity. 
D)  an enzyme with more than one subunit. 
E)  the need for cofactors. 
A)  lack of cooperativity. 
B)  feedback inhibition. 
C)  activating activity. 
D)  an enzyme with more than one subunit. 
E)  the need for cofactors.

Question 17

The following questions are based on the reaction A + B ↔ C + D shown in Figure 6.4.
   Figure 6.4
-Which of the following represents the activation energy needed for the enzyme-catalyzed reverse reaction, C + D → A + B, in Figure 6.4?

Accepted Answer

A)  a 
B)  b 
C)  c 
D)  d 
E)  e 
A)  a 
B)  b 
C)  c 
D)  d 
E)  e

Question 18

The following questions are based on the reaction A + B ↔ C + D shown in Figure 6.4.
   Figure 6.4
-Which of the following represents the difference between the free-energy content of the reactants and the free-energy content of the products in Figure 6.4?

Accepted Answer

A)  a 
B)  b 
C)  c 
D)  d 
E)  e 
A)  a 
B)  b 
C)  c 
D)  d 
E)  e

Question 19

Which of the following is true for all exergonic reactions?

Accepted Answer

A)  The products have more total energy than the reactants. 
B)  The reaction proceeds with a net release of free energy. 
C)  The reaction goes only in a forward direction: all reactants will be converted to products, but no products will be converted to reactants. 
D)  A net input of energy from the surroundings is required for the reactions to proceed. 
E)  The reactions are rapid. 
A)  The products have more total energy than the reactants. 
B)  The reaction proceeds with a net release of free energy. 
C)  The reaction goes only in a forward direction: all reactants will be converted to products, but no products will be converted to reactants. 
D)  A net input of energy from the surroundings is required for the reactions to proceed. 
E)  The reactions are rapid.

Question 20

Zinc, an essential trace element for most organisms, is present in the active site of the enzyme carboxypeptidase. The zinc most likely functions as a(n)

Accepted Answer

A)  competitive inhibitor of the enzyme. 
B)  noncompetitive inhibitor of the enzyme. 
C)  allosteric activator of the enzyme. 
D)  cofactor necessary for enzyme activity. 
E)  coenzyme derived from a vitamin. 
A)  competitive inhibitor of the enzyme. 
B)  noncompetitive inhibitor of the enzyme. 
C)  allosteric activator of the enzyme. 
D)  cofactor necessary for enzyme activity. 
E)  coenzyme derived from a vitamin.

Exam 6: An Introduction to Metabolism

If an enzyme is added to a solution where its substrate and product are in equilibrium, what will occur?

Which of the following is an example of potential rather than kinetic energy?

Protein kinases are enzymes that transfer the terminal phosphate from ATP to an amino acid residue on the target protein. Many are located on the plasma membrane as integral membrane proteins or peripheral membrane proteins. What purpose may be served by their plasma membrane localization?

During a laboratory experiment, you discover that an enzyme-catalyzed reaction has a ∆G of -20 kcal/mol. If you double the amount of enzyme in the reaction, what will be the ∆G for the new reaction?

Which of the following is a statement of the first law of thermodynamics?

Which of the following statements is true about enzyme-catalyzed reactions?

The mechanism in which the end product of a metabolic pathway inhibits an earlier step in the pathway is most precisely described as

Which of the following metabolic processes can occur without a net influx of energy from some other process?

Chemical equilibrium is relatively rare in living cells. Which of the following could be an example of a reaction at chemical equilibrium in a cell?

A chemical reaction that has a positive ΔG is best described as

Figure 6.1 -How do cells use the ATP cycle shown in Figure 6.1?

Which of the following statements is representative of the second law of thermodynamics?

Besides turning enzymes on or off, what other means does a cell use to control enzymatic activity?

Allosteric enzyme regulation is usually associated with

The following questions are based on the reaction A + B ↔ C + D shown in Figure 6.4. Figure 6.4 -Which of the following represents the activation energy needed for the enzyme-catalyzed reverse reaction, C + D → A + B, in Figure 6.4?

The following questions are based on the reaction A + B ↔ C + D shown in Figure 6.4. Figure 6.4 -Which of the following represents the difference between the free-energy content of the reactants and the free-energy content of the products in Figure 6.4?

Which of the following is true for all exergonic reactions?

Zinc, an essential trace element for most organisms, is present in the active site of the enzyme carboxypeptidase. The zinc most likely functions as a(n)

Introduction: Evolution and the Foundations of Biology

The Chemical Context of Life

Carbon and the Molecular Diversity of Life

A Tour of the Cell

Membrane Transport and Cell Signaling

Cellular Respiration and Fermentation

Photosynthesis

The Cell Cycle

Meiosis and Sexual Life Cycles

Mendel and the Gene Idea

The Chromosomal Basis of Inheritance

The Molecular Basis of Inheritance

Gene Expression: From Gene to Protein

Regulation of Gene Expression

Development, Stem Cells, and Cancer

Viruses

Genomes and Their Evolution

Descent With Modification

Phylogeny

The Evolution of Populations

The Origin of Species

Broad Patterns of Evolution

Early Life and the Diversification of Prokaryotes

The Origin and Diversification of Eukaryotes

The Colonization of Land by Plants and Fungi

The Rise of Animal Diversity

Plant Structure and Growth

Resource Acquisition, Nutrition, and Transport in Vascular Plants

Reproduction and Domestication of Flowering Plants

Plant Responses to Internal and External Signals

Homeostasis and Endocrine Signaling

Animal Nutrition

Circulation and Gas Exchange

The Immune System

Reproduction and Development

Neurons, Synapses, and Signaling

Nervous and Sensory Systems

Motor Mechanisms and Behavior

Population Ecology and the Distribution of Organisms

Species Interactions

Ecosystems and Energy

Global Ecology and Conservation Biology

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