Bio 006 Exam #2 MC Chapter 8

Chapter 8 Practice Test Questions (40) & Chapter 8 Quiz (10)

Which of the following statements best describes metabolism in its entirety in all organisms?

Metabolism depends on a constant supply of energy from food.

Metabolism uses all of an organism's resources.

Metabolism consists of all the energy transformation reactions in an organism.

Metabolism manages the increase of entropy in an organism.

Metabolism consists of all the energy transformation reactions in an organism.

Which of the following types of reactions would decrease the entropy within a cell?

anabolic reactions

digestion

catabolic reactions

hydrolysis

anabolic reactions

Which of the terms below best describes a regulatory mechanism in which the end product of a metabolic pathway inhibits an enzyme that catalyzes an early step in the pathway?

feedback inhibition

cooperative inhibition

allosteric inhibition

metabolic inhibition

feedback inhibition

Which of the following statements best describes the first law of thermodynamics?

Energy cannot be created or destroyed.

The entropy of the universe is decreasing.

Energy cannot be transferred or transformed.

The entropy of the universe is constant.

Energy cannot be created or destroyed.

Which of the following statements best describes a system at chemical equilibrium?

The system releases energy at a steady rate.

The system consumes energy at a steady rate.

The system can do no work.

The kinetic energy of the system is zero.

The system can do no work.

Disruption of the active site of an enzyme would most likely result in which of the following?

A decreased ability of the enzyme to bind products.

A decreased ability of the enzyme to bind substrates.

An increase in the rate of the reaction catalyzed by the enzyme.

A decreased ability of the enzyme to bind allosteric regulators.

A decreased ability of the enzyme to bind substrates.

When chemical, transport, or mechanical work is performed by an organism, what happens to the heat that is generated?

It is used to generate ADP from nucleotide precursors.

It is lost to the environment.

It is captured to store energy as more ATP.

It is used to power yet more cellular work.

It is lost to the environment.

What is the name of the barrier that must be overcome before products are formed in a spontaneous reaction?

entropy

free energy

activation energy

the equilibrium point

activation energy

Which of the following statements best describes an exergonic reaction?

The reaction goes only in a forward direction: all reactants will be converted to products, but no products will be converted to reactants.

The products have more total energy than the reactants.

A net input of energy from the surroundings is required for the reaction to proceed.

The reaction proceeds with a net release of free energy.

The reaction proceeds with a net release of free energy.

Which of the following statements best describes induced fit?

Binding of an activator molecule changes the shape of the active site of an enzyme.

The conformation of the active site is determined by the tertiary or quaternary structure of the enzyme.

Substrate binds to an allosteric site rather than to the active site of an enzyme.

Binding of substrate to the active site changes the shape of the active site of an enzyme.

Binding of substrate to the active site changes the shape of the active site of an enzyme.

Which of the following correctly states the relationship between anabolic and catabolic pathways?

Degradation of organic molecules by anabolic pathways provides the energy to drive catabolic pathways.

Energy derived from catabolic pathways is used to drive the breakdown of organic molecules in anabolic pathways.

The flow of energy between catabolic and anabolic pathways is reversible.

Anabolic pathways synthesize more complex organic molecules using the energy derived from catabolic pathways.

Catabolic pathways produce usable cellular energy by synthesizing more complex organic molecules.

Anabolic pathways synthesize more complex organic molecules using the energy derived from catabolic pathways.

Organisms are described as thermodynamically open systems. Which of the following statements is consistent with this description?

The metabolism of an organism is isolated from its surroundings.

Because energy must be conserved, organisms constantly recycle energy and thus need no input of energy.

Organisms acquire energy from and lose energy to their surroundings.

Heat produced by the organism is conserved in the organism and not lost to the environment.

All of the listed responses are correct.

Organisms acquire energy from and lose energy to their surroundings.

Consider the growth of a farmer's crop over a season. Which of the following correctly states a limitation imposed by the first or second law of thermodynamics? (Concept 8.1)

Growth of the crops must occur spontaneously.

The entropy of the universe must decrease to account for the increased entropy associated with plant growth.

To obey the first law, the crops must represent an open system.

The process of photosynthesis produces energy that the plant uses to grow.

All of the listed responses are correct.

To obey the first law, the crops must represent an open system.

Which of the following states the relevance of the first law of thermodynamics to biology? (Concept 8.1)

Energy is destroyed as glucose is broken down during cellular respiration.

Because living things consume energy, the total energy of the universe is constantly decreasing.

Energy can be freely transformed among different forms as long as the total energy is conserved.

Living organisms must increase the entropy of their surroundings.

Photosynthetic organisms produce energy in sugars from sunlight

Energy can be freely transformed among different forms as long as the total energy is conserved.

Which of the following is an example of the second law of thermodynamics as it applies to biological reactions? (Concept 8.1)

The aerobic respiration of one molecule of glucose produces six molecules each of carbon dioxide and water.

All types of cellular respiration produce ATP.

Cellular respiration releases some energy as heat.

The first and second choices are correct.

The first, second, and third choices are correct.

The aerobic respiration of one molecule of glucose produces six molecules each of carbon dioxide and water.

According to the second law of thermodynamics, which of the following is true? (Concept 8.1)

Energy conversions increase the order in the universe.

The decrease in entropy associated with life must be compensated for by increased entropy in the environment in which life exists.

The total amount of energy in the universe is constant.

The entropy of the universe is constantly decreasing.

All reactions produce some heat.

The decrease in entropy associated with life must be compensated for by increased entropy in the environment in which life exists.

If the entropy of a living organism is decreasing, which of the following is most likely to be occurring simultaneously? (Concept 8.2)

The entropy of the organism's environment must also be decreasing.

In this situation, the second law of thermodynamics must not apply.

Energy input into the organism must be occurring to drive the decrease in entropy.

Heat is being used by the organism as a source of energy.

The first law of thermodynamics is being violated.

Energy input into the organism must be occurring to drive the decrease in entropy.

Which part of the equation ΔG = ΔH – TΔS tells you if a process is spontaneous? (Concept 8.2)

ΔS

All of these values reveal the direction in which a reaction will go.

ΔG

ΔH

TΔS

ΔG

If, during a process, the system becomes more ordered, then __________. (Concept 8.2)

ΔG is negative

ΔH is negative

ΔS is negative

ΔG is positive

ΔH is positive

ΔS is negative

When one molecule is broken down into six component molecules, which of the following will always be true? (Concept 8.2)

An input of free energy is needed.

ΔS is negative.

ΔH is negative.

ΔG is positive.

ΔS is positive.

ΔS is positive.

From the equation ΔG = ΔH – TΔS it is clear that __________. (Concept 8.2)

a decrease in the system's total energy will increase the probability of spontaneous change

a decrease in the system's total energy will increase the probability of spontaneous change, and increasing the entropy of a system will increase the probability of spontaneous change

increasing the temperature of a system will increase the probability of spontaneous change

increasing the entropy of a system will increase the probability of spontaneous change

a decrease in the system's total energy will increase the probability of spontaneous change, increasing the entropy of a system will increase the probability of spontaneous change, and increasing the temperature of a system will increase the probability of spontaneous change

a decrease in the system's total energy will increase the probability of spontaneous change, increasing the entropy of a system will increase the probability of spontaneous change, and increasing the temperature of a system will increase the probability of spontaneous change

An exergonic (spontaneous) reaction is a chemical reaction that __________. (Concept 8.2)

cannot occur outside of a living cell

occurs only when an enzyme or other catalyst is present

leads to a decrease in the entropy of the universe

is common in anabolic pathways

releases energy when proceeding in the forward direction

releases energy when proceeding in the forward direction

Which of the following reactions would be endergonic? (Concept 8.2)

ATP → ADP + Pi

C6H12O6 + 6 O2 → 6 CO2 + 6 H2O

HCl → H+ + Cl-

glucose + fructose → sucrose

All of the listed responses are correct.

glucose + fructose → sucrose

Molecules A and B contain 110 kcal/mol of free energy, and molecules C and D contain 150 kcal/mol of energy. A and B are converted to C and D. What can be concluded? (Concept 8.2)

The conversion of A and B to C and D is spontaneous.

The conversion of A and B to C and D is exergonic; the products are less organized than the reactants.

The entropy in the products, C and D, is higher than in the reactants, A and B.

The reaction that proceeds to convert A and B to C and D is endergonic; the products are more organized than the reactants.

A and B will be converted to C and D with a net release of energy.

The reaction that proceeds to convert A and B to C and D is endergonic; the products are more organized than the reactants.

Which of the following determines the sign of ΔG for a reaction? (Concept 8.2)

The enzyme catalyzing the reaction’s having a high affinity (strength of binding) for the reactants

The free energy of the reactants

The enzyme catalyzing the reaction’s having a low affinity for the products

The free energy of the reactants and the free energy of the products

The free energy of the products

The free energy of the reactants and the free energy of the products

Metabolic pathways in cells are typically far from equilibrium. Which of the following processes tend(s) to keep these pathways away from equilibrium? (Concept 8.2)

The continuous removal of the products of a pathway to be used in other reactions

An input of free energy from outside the pathway

An input of heat from the environment

The first and second listed responses are correct.

The first, second, and third listed responses are correct.

The first and second listed responses are correct.

The free energy derived from the hydrolysis of ATP can be used to perform many kinds of cellular work. Which of the following is an example of the cellular work involved in the production of electrochemical gradients? (Concept 8.3)

The beating of cilia

The chemical synthesis of ATP

Proton movement against a gradient of protons

Facilitated diffusion

Chromosome movement on microtubules

Proton movement against a gradient of protons

In general, the hydrolysis of ATP drives cellular work by __________. (Concept 8.3)

lowering the activation energy of the reaction

changing to ADP and phosphate

acting as a catalyst

releasing free energy that can be coupled to other reactions

releasing heat

releasing free energy that can be coupled to other reactions

Much of the suitability of ATP as an energy intermediary is related to the instability of the bonds between the phosphate groups. These bonds are unstable because __________. (Concept 8.3)

the phosphate groups are polar and are attracted to the water in the cell's interior

the bonds between the phosphate groups are unusually strong and breaking them releases free energy

the valence electrons in the phosphorus atom have less energy on average than those of other atoms

they are hydrogen bonds, which are only about 10% as strong as covalent bonds

the negatively charged phosphate groups vigorously repel one another and the terminal phosphate group is more stable in water than it is in ATP

the negatively charged phosphate groups vigorously repel one another and the terminal phosphate group is more stable in water than it is in ATP

When 1 mole of ATP is hydrolyzed in a test tube without an enzyme, about twice as much heat is given off as when 1 mole of ATP is hydrolyzed in a cell. Which of the following best explains these observations? (Concept 8.3)

Cells are less efficient at energy metabolism than reactions that are optimized in a test tube.

In cells, ATP is hydrolyzed to ADP and Pi, but in the test tube it is hydrolyzed to carbon dioxide and water.

In the cell, the hydrolysis of ATP is coupled to other endergonic reactions.

The amount of heat released by a reaction has nothing to do with the free energy change of the reaction.

Cells have the ability to store heat; this cannot happen in a test tube.

In the cell, the hydrolysis of ATP is coupled to other endergonic reactions.

Which of the following best characterizes the role of ATP in cellular metabolism? (Concept 8.3)

The charge on the phosphate group of ATP tends to make the molecule very water-soluble.

It is catabolized to carbon dioxide and water.

The free energy released by ATP hydrolysis may be coupled to an endergonic process via the formation of a phosphorylated intermediate.

The release of free energy during the hydrolysis of ATP heats the surrounding environment.

The DG associated with its hydrolysis is positive.

The free energy released by ATP hydrolysis may be coupled to an endergonic process via the formation of a phosphorylated intermediate.

The formation of glucose-6-phosphate from glucose is an endergonic reaction and is coupled to which of the following reactions or pathways? (Concept 8.3)

The active transport of a phosphate ion into the cell

The formation of ATP from ADP + Pi

The conversion of glucose + fructose to make sucrose

The hydrolysis of ATP

The contraction of a muscle cell

The hydrolysis of ATP

A chemical reaction is designated as exergonic rather than endergonic when __________. (Concept 8.2) and (Concept 8.4)

the products are less complex than the reactants

the potential energy of the products is less than the potential energy of the reactants

activation energy exceeds net energy release

it absorbs more energy

activation energy is required

the potential energy of the products is less than the potential energy of the reactants

Which of the following is changed by the presence of an enzyme in a reaction? (Concept 8.2) and (Concept 8.4)

The activation energy

The sign of ΔG

The magnitude of ΔG

The G value for the products

The G value for the reactants

The activation energy

What do the sign and magnitude of the ΔG of a reaction tell us about the speed of the reaction? (Concept 8.2) and (Concept 8.4)

The sign determines whether the reaction is spontaneous, and the magnitude determines the speed.

The more negative the ΔG, the faster the reaction is.

The sign does not matter, but the smaller the magnitude of ΔG, the faster the reaction.

The sign does not matter, but the larger the magnitude of ΔG, the faster the reaction.

Neither the sign nor the magnitude of ΔG has anything to do with the speed of a reaction.

Neither the sign nor the magnitude of ΔG has anything to do with the speed of a reaction.

How do enzymes lower activation energy? (Concept 8.4)

By increasing reactivity of products

By locally concentrating the reactants

By harnessing heat energy to drive the breakage of bonds between atoms

The first two responses are correct.

The second and third choices are correct.

By locally concentrating the reactants

Which of the following statements about enzymes is/are true? (Concept 8.4)

Enzymes speed up the rate of the reaction without changing the DG for the reaction.

The more heat that is added to a reaction, the faster the enzymes will function.

Enzymes react with their substrate (form chemical bonds), forming an enzyme-substrate complex, which irreversibly alters the enzyme.

All of the listed responses are correct.

Enzymes increase the rate of a reaction by raising the activation energy for reactions.

Enzymes speed up the rate of the reaction without changing the DG for the reaction.

Which of the following statements about enzyme function is correct? (Concept 8.4)

Enzymes can lower the activation energy of reactions, but they cannot change the equilibrium point because they cannot change the net energy output.

Enzymes can greatly speed up reactions, but they cannot change the activation energy because they cannot change the net energy output.

Enzymes can change the equilibrium point of reactions, but they cannot speed up reactions because they cannot change the net energy output.

None of the listed responses is correct.

Enzymes can greatly speed up reactions, but they cannot change the net energy output because they cannot change the activation energy.

Enzymes can lower the activation energy of reactions, but they cannot change the equilibrium point because they cannot change the net energy output.

A plot of reaction rate (velocity) against temperature for an enzyme indicates little activity at 10°C and 45°C, with peak activity at 35°C. The most reasonable explanation for the low velocity at 10°C is that __________. (Concept 8.4)

the cofactors required by the enzyme system lack the thermal energy required to activate the enzyme

the hydrogen bonds that define the structure of the enzyme's active site are unstable

the enzyme was denatured

there is too little activation energy available

the substrate becomes a competitive inhibitor at lower temperature

there is too little activation energy available

Which of the following statements about enzymes is incorrect? (Concept 8.4)

Most enzymes are proteins.

Enzymes can be used to accelerate both anabolic and catabolic reactions.

An enzyme lowers the activation energy of a chemical reaction.

An enzyme is very specific in terms of the substrate to which it binds.

An enzyme is consumed during the reaction it catalyzes.

An enzyme is consumed during the reaction it catalyzes.

Which of the following statements about the active site of an enzyme is correct? (Concept 8.4)

The active site allows the reaction to occur under the same environmental conditions as the reaction without the enzyme.

The structure of the active site is not affected by changes in temperature.

Coenzymes are rarely found in the active site of an enzyme.

The active site may resemble a groove or pocket in the surface of a protein into which the substrate fits.

The active site has a fixed structure (shape).

The active site may resemble a groove or pocket in the surface of a protein into which the substrate fits.

What is meant by the "induced fit" of an enzyme? (Concept 8.4)

The shape of the active site is nearly perfect for specifically binding the enzyme's substrate or substrates.

The enzyme changes its shape slightly as the substrate binds to it.

The presence of the substrate in solution induces the enzyme to slightly change its structure.

The enzyme structure is altered so that it can be induced to fit many different types of substrate.

The substrate can be altered so that it is induced to fit into the enzyme's active site.

The enzyme changes its shape slightly as the substrate binds to it.

Which of the following statements correctly describe(s) the role or roles of heat in biological reactions? (Concept 8.4)

Heat from the environment is necessary for substrates to get over the activation energy barrier.

The kinetic energy of the substrates is increased as the amount of heat in the system is increased.

Increasing the amount of heat in a system will always increase the rate of enzyme-catalyzed reactions.

The first and second choices are correct.

The second and third choices are correct.

The first and second choices are correct.

Which of the following environments or actions would not affect the rate of an enzyme reaction? (Concept 8.4)

Heating the enzyme

None of the listed responses is correct.

Cooling the enzyme

Substrate concentration

pH

None of the listed responses is correct.

Enzyme activity is affected by pH because __________. (Concept 8.4)

most substrates do not function well at high or low pH

changes in pH can cause loss of cofactors from the enzyme

low pH will denature all enzymes

the binding of hydrogen ions to the enzyme absorbs energy and thus there may not be enough energy to overcome the activation energy barrier

high or low pH may disrupt hydrogen bonding or ionic interactions and thus change the shape of the active site

high or low pH may disrupt hydrogen bonding or ionic interactions and thus change the shape of the active site

Which of these statements about enzyme inhibitors is true? (Concept 8.4)

A noncompetitive inhibitor does not change the shape of the active site.

A competitive inhibitor binds to the enzyme at a place that is separate from the active site.

Inhibition of enzyme function by compounds that are not substrates is something that only occurs under controlled conditions in the laboratory.

When the product of an enzyme or an enzyme sequence acts as its inhibitor, this is known as positive feedback.

The action of competitive inhibitors may be reversible or irreversible.

The action of competitive inhibitors may be reversible or irreversible.

Succinylcholine is structurally almost identical to acetylcholine. If succinylcholine is added to a mixture that contains acetylcholine and the enzyme that hydrolyzes acetylcholine (but not succinylcholine), the rate of acetylcholine hydrolysis is decreased. Subsequent addition of more acetylcholine restores the original rate of acetylcholine hydrolysis. Which of the following correctly explains this observation? (Concept 8.4)

Succinylcholine must be a competitive inhibitor with acetylcholine.

Succinylcholine must be a noncompetitive inhibitor.

Succinylcholine must be an allosteric regulator for this enzyme.

The active site must have the wrong configuration to permit succinylcholine binding.

The presence of succinylcholine changes the conditions in the solution, resulting in a denaturation of the enzyme.

Succinylcholine must be a competitive inhibitor with acetylcholine.

The process of stabilizing the structure of an enzyme in its active form by the binding of a molecule outside the active site is an example of __________. (Concept 8.5)

competitive inhibition

allosteric activation

noncompetitive inhibition

feedback inhibition

cooperativity

allosteric activation

Which of the following statements about allosteric proteins is/are true? (Concept 8.5)

They are acted on by inhibitors.

They are sensitive to environmental conditions.

None of the first three listed responses is correct.

All of the first three listed responses are correct.

They exist in active and inactive conformations.

All of the first three listed responses are correct.

The binding of an allosteric inhibitor to an enzyme causes the rate of product formation by the enzyme to decrease. Which of the following best explains why this decrease occurs? (Concept 8.5)

The allosteric inhibitor binds to the active site, preventing the substrate from binding.

The allosteric inhibitor causes free energy change of the reaction to increase.

The allosteric inhibitor causes a structural change in the enzyme that prevents the substrate from binding at the active site.

The allosteric inhibitor lowers the temperature of the active site.

The allosteric inhibitor binds to the substrate and prevents it from binding at the active site.

The allosteric inhibitor causes a structural change in the enzyme that prevents the substrate from binding at the active site.