Chapter Quiz
1.  

Which of the following situations does NOT represent a transformation of one type of energy to another? (p. 88)


the burning of gasoline in a car engine

the production of sugar by photosynthesis

the production of electrical power by damming a river

cracking a nut by using a nutcracker

plugging a stereo into a wall socket to play music


2.  

What is energy? (p. 88)


the capacity to perform work

the amount of food eaten

movement

the rearrangement of chemical molecules within matter

the capacity to produce heat


3.  

Energy is most commonly stored in plants as ____________. (p. 89)


electrical energy

mechanical energy

electromagnetic energy

kinetic energy

chemical energy


4.  

Organisms are described as thermodynamically open systems. This means that _____. (p. 89)


the metabolism of an organism is isolated from its surroundings

organisms can reverse the increase in entropy

organisms acquire energy from their surroundings

organisms are capable of circumventing the second law of thermodynamics

because energy is conserved, organisms do not require energy input from their surroundings


5.  

According to the second law of thermodynamics, which of the following is true? (p. 90)


Energy conversions increase the order in the universe.

The total amount of energy in the universe is constant.

The ordering of one system depends on the disordering of another.

The entropy of the universe is constantly decreasing.

All reactions produce some heat.


6.  

Which one of the following is an example of the second law of thermodynamics? (p. 90)


The aerobic respiration of glucose generates heat.

All types of cellular respiration produce ATP.

CO2 is exhaled as a by-product of aerobic respiration.

Photosynthesis enables plants to create energy from sunlight.

Energy is stored during the Calvin cycle.


7.  

If the entropy of a system is increasing, this means that ____________. (p. 90)


the sun's energy is being captured by photosynthesis

heat is being used by organisms as a source of energy

the first law of thermodynamics is being violated

energy input will be needed to maintain organization

the amount of usable energy in the system is increasing


8.  

The first law of thermodynamics ____________. (p. 89)


deals with entropy

states that energy is neither created nor destroyed

deals with heat content

states that entropy spontaneously increases

predicts the direction of a reaction


9.  

Which one of the following is NOT true about the second law of thermodynamics? (p. 90)


It states that energy is neither created nor destroyed.

It deals with entropy.

It deals with heat content.

It deals with spontaneity.

All the above are true.


10.  

Which one of the following has the most free energy per molecule? (p. 91)


a sugar molecule

an amino acid molecule

a starch molecule

a fatty acid molecule

a cholesterol molecule


11.  

From the equation DG = DH - TDS it is clear that _____. (p. 92)


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

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

the capacity of a system to perform work is related to the total energy of the system

all of the above are true


12.  

What must be true if the reaction AB + CD —> AC + BD occurs spontaneously? (p. 91)


The DG of the reaction must be negative.

The reaction must be exergonic.

The environment has adequate thermal energy to meet the activation energy requirement.

The bonds must have absorbed enough energy to become unstable.

All of the above are true.


13.  

Which of the following reactions would be endergonic? (p. 92)


HCl —> H+ + Cl-

C6H12O6 + 6 O2 —> 6 CO2 + 6 H2O

ATP —> ADP + Pi

maltose + fructose —> sucrose

all of the above


14.  

Which one of the following tells us, without additional information, the way a process will go spontaneously? (p. 92)


DG

DH

DS

TDS

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


15.  

If, during a process, the system becomes more ordered, then ____________. (p. 92)


DG is negative

DG is positive

DH is negative

DH is positive

TDS is negative


16.  

An exergonic (spontaneous) reaction is a chemical reaction that ____________. (p. 92)


occurs only when an enzyme is present

occurs within living cells but not in a test tube

releases energy when proceeding in the forward direction

occurs in all living cells

all of the above


17.  

When one molecule is broken down into six component molecules, which one of the following is definitely true? (p. 92)


Outside energy is needed.

DG is positive.

DH is negative.

DS is positive.

DS is negative.


18.  

When DG is positive, the reaction or process can be termed ___________. (p. 92)


endergonic

exergonic

exothermic

endothermic

enthalpic


19.  

A reaction is designated as exergonic rather than endergonic when ___________. (p. 92)


activation energy is necessary

no kinetic energy is released

activation energy exceeds net energy release

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

it absorbs more energy


20.  

What best characterizes the role of ATP in cellular metabolism? (p. 94)


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

Its free energy is coupled to an endergonic process via the formation of a phosphorylated intermediate.

It is catabolized to carbon dioxide and water.

The DG associated with its hydrolysis is positive.

The polar phosphate groups assist in the alignment of polar substrates as they enter an enzyme's active site.


21.  

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 _____. (p. 95)


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

the negatively charged phosphate groups vigorously repel one another

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

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

all of the above


22.  

Which monomer could be most easily modified to form ATP? (p. 94)


the RNA nucleotide adenosine

the amino acid tryptophan

the DNA nucleotide adenosine

cholesterol

the monosaccharide galactose


23.  

___________ is an example of the cellular work accomplished with the free energy of ATP hydrolysis. (p. 94)


Mechanical work, such as the beating of cilia,

Transport work, such as the movement of glucose into an adipose cell,

Chemical work, such as the synthesis of new protein,

Mechanical work, such as pumping blood through the circulatory system,

all of the above


24.  

The formation of glucose-6-phosphate from glucose is coupled to the reaction ____________. (p. 95)


ATP —> ATP + Pi

ADP —> ATP + Pi

ATP —> ADP

ADP —> ATP

ADP + Pi —> ATP


25.  

In general, the hydrolysis of ATP drives cellular work by _____. (p. 95)


changing to ADP and phosphate

transferring a phosphate group to some other molecule

releasing heat

acting as a catalyst

lowering the free energy of the reaction


26.  

The mechanism of enzyme action is _____. (p. 97)


to create an energy barrier between substrates

to lower the energy of the activation of a reaction

to change the direction of thermodynamic equilibrium

to change endergonic into exergonic reactions

to allow substrates to move more freely in solution


27.  

Which of the following statements about enzymes is true? (p. 96)


Enzymes raise the activation energy for reactions.

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

Most enzymes are chains of amino acids.

Only the most efficient enzymes can catalyze reactions in either direction.

The more a reaction is heated, the faster the enzymes will function.


28.  

What is meant by the induced fit of an enzyme? (p. 98)


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

The enzyme is altered so it is induced to fit many different types of substrate.

Several sites on an enzyme can be induced to act on a substrate.

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

All of the above.


29.  

Three or four of the following statements concerning enzymes are true and correct. Which one, if any, is NOT correct? If all the statements are correct, choose "All of the above." (p. 96)


Most enzymes are proteins.

An enzyme is not consumed by the catalytic process.

An enzyme is very specific in terms of which substrates it can bind to.

An enzyme lowers the activation energy of a chemical reaction.

All of the above.


30.  

The active site of an enzyme _____. (p. 98)


has a rigid shape, which does not change

is where the coenzyme will never be found

resembles a groove or crevice into which the substrate fits

is the place where both apoenzymes join

fits the substrate as a lock and key


31.  

Enzymes can __________, but they cannot __________ because they cannot __________. (p. 97)


greatly speed up reactions ... change the net energy output ... change the activation energy

change the equilibrium point of reactions ... speed up reactions ... change the net energy output

greatly speed up reactions ... change the activation energy ... change the net energy output

lower the activation energy of reactions ... change the equilibrium point ... change the net energy output

none of the above


32.  

A plot of reaction rate (velocity) against temperature for an enzyme indicates little activity at 0°C and 45°C, with peak activity at 35°C. The most reasonable explanation for the low velocity at 0°C is that _____. (p. 100)


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

the substrate becomes an allosteric regulator

the enzyme was denatured

the co-factors required by the enzyme system lack the thermal energy required to activate the enzyme

there is too little activation energy available


33.  

Succinylcholine is structurally almost identical to acetylcholine, but if combined with the enzyme that normally hydrolyzes acetylcholine, the enzyme is no longer able to hydrolyze acetylcholine. This suggests that _____. (p. 100)


succinylcholine must be a competitive inhibitor with acetylcholine

succinylcholine must be an allosteric regulator for this enzyme

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

succinylcholine must be a noncompetitive inhibitor

the activation energy barrier for succinylcholine hydrolysis is higher than for acetylcholine hydrolysis


34.  

Which of the following environments or actions does NOT affect enzyme activity? (p. 99)


heating the enzyme

cooling the enzyme

salt concentration

pH

All of the above can affect enzyme activity.


35.  

Which of these statements about enzyme inhibitors is true? (p. 100)


A competitive inhibitor binds to the enzyme outside the active site.

The action of competitive inhibitors may be reversible or irreversible.

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

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

Antibiotics and pesticides generally do not act on enzymes, but rather affect the genetic code of their victims.


36.  

pH can affect enzyme activity because _____. (p. 100)


most substrates don't function well at high or low pH

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

high or low pH may cause the active site to lose its energy

excess hydrogen ions can combine with the substrate and cause the reaction to go more slowly

hydrogen ions absorb energy and thus there may not be enough energy to get the reaction started.


37.  

A competitive inhibitor competes with the __________ at the __________ of an enzyme. (p. 100)


product ... active site

product ... allosteric site

substrate ... active site

substrate ... allosteric site

substrate ... active site and allosteric site


38.  

The process of stabilizing the quaternary structure of an enzyme in its active form by the binding of a molecule is an example of _____. (p. 101)


feedback inhibition

competitive inhibition

allosteric regulation

the participation of a co-factor

cooperativity


39.  

Which, if any, of the following statements is NOT true about allosteric proteins? (p. 101)


They are sensitive to environmental conditions.

They are acted on by inhibitors.

They exist in active and inactive conformations.

They have more than one subunit.

All of the above statements are true of allosteric proteins.


40.  

In an enzyme molecule with multiple subunits, the binding of one substrate molecule to the active site of one subunit causes all the subunits to assume their active conformation, via the mechanism of induced fit. This is called ____________. (p. 102)


allosteric activation

allosteric inhibition

competitive inhibition

cooperativity

feedback inhibition

   



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