Ch19 PT - Weebly

Ch19_PT

MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.

1) Enzymes are members of which class of biomolecules?

A) carbohydrates

B) nucleic acids

C) proteins

D) steroids

E) lipids

1)

2) What is the function of enzymes?

A) biochemical catalysts

B) structure and support

C) communication between cells

D) nutritional reserves

E) physical protection

2)

3) The reactant in an enzyme-catalyzed reaction is called the

A) hormone.

B) inhibitor.

C) cofactor.

3)

D) substrate.

E) vitamin.

4) All of the following phrases correctly describes enzymes except

A) dissolve in water.

B) act as catalysts.

C) contain an active site.

D) have a globular shape.

E) behave as substrates.

4)

5) The tertiary structure of most enzymes is

A) a ¦Â-pleated sheet.

B) globular.

C) an ¦Á-helix.

D) fibrous.

E) none of these.

5)

6) The maximum number of substrate molecules that one enzyme molecule can act on in a given unit

of time is the

A) turnover number.

B) equilibrium constant.

C) catalytic multiplier.

D) rate constant.

E) reduction factor.

6)

7) Which term identifies the relatively small portion of the enzyme that is directly involved in the

biochemical reaction being catalyzed?

A) substrate

B) precursor

C) C-terminal

D) active site

E) N-terminal

7)

1

8) Enzymes function as catalysts by

A) becoming one of the reactants.

B) changing the value of the equilibrium constant to a more favorable value.

C) lowering the value of the activation energy.

D) increasing the amount of time needed to reach equilibrium.

E) changing the value of the free energy change to a more favorable value.

8)

SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.

9) Explain the term specificity as it applies to enzyme activity.

9)

MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.

10) The nonprotein portion required by some enzymes for proper functioning is called a(an)

A) zymogen.

B) activator.

C) inhibitor.

D) cofactor.

E) substrate.

10)

11) Which aspect of enzyme structure is related to our dietary need for trace minerals?

A) cofactor

B) chirality

C) active site

D) turnover number

E) none of these

11)

12) The name of an enzyme can often be recognized by the ending

A) -ase.

B) -ose.

C) -ate.

D) -ene.

12)

E) -ic acid.

13) An enzyme that catalyzes addition or removal of hydrogen or oxygen on substrate molecules is

a(an) ________.

A) hydrolase

B) ligase

C) transferase

D) oxidoreductase

E) isomerase

13)

14) An enzyme that is classified as a hydrolase is involved in ________ reactions.

A) reduction

B) polymerization

C) isomerization

D) oxidation

E) hydrolysis

14)

15) Transaminase can be classified as a(an) ________ because its function is moving an amine group

from one molecule to another.

A) ligase

B) oxidoreductase

C) isomerase

D) transferase

E) hydrolase

15)

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16) A synthetase can be classified as a(an) ________ because its function is joining two molecules

together.

A) isomerase

B) oxidoreductase

C) hydrolase

D) transferase

E) ligase

16)

17) An enzyme that catalyzes the conversion of a cis double bond to a trans double bond is classified as

a(an)

A) hydrolase.

B) transferase.

C) ligase.

D) oxidoreductase.

E) isomerase.

17)

18) The theory of enzyme mechanism that suggests a rigid, inflexible molecule is the ________ model.

A) substrate specific

B) lock-and-key

C) active site

D) induced-fit

E) coenzyme

18)

19) The theory of enzyme mechanism that suggests a flexible molecule whose shape is altered by the

reaction conditions is the ________ model.

A) lock-and-key

B) induced-fit

C) substrate specific

D) active site

E) coenzyme

19)

20) Which factor is not important in explaining how enzymes work?

A) The bonds in substrates are subjected to strains which weaken them.

B) Substrates are brought into solution more easily.

C) Two different substrate molecules are brought into close contact.

D) Substrates are forced into the correct orientation for interaction.

E) Substrates are placed near acidic or basic sites.

20)

21) When substrate molecules occupy all of the active sites in the enzyme available for a particular

reaction, the enzyme is said to be

A) activated.

B) inhibited.

C) saturated.

D) denatured.

E) hydrolyzed.

21)

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22) In a normal biochemical system, the rate of a specific reaction is determined by

A) enzyme efficiency and substrate concentration.

B) pH and temperature.

C) temperature and substrate concentration.

D) pH and enzyme efficiency.

E) temperature and enzyme efficiency.

22)

23) When an enzyme is saturated it

A) is in low concentration relative to the substrate, and the reaction rate is directly proportional

to enzyme concentration.

B) is in high concentration relative to the substrate, and the reaction rate is directly proportional

to substrate concentration.

C) is in low concentration relative to the substrate, and the reaction rate approaches its

maximum.

D) has been completely consumed, and that reaction cannot occur again until new enzymes are

produced.

E) none of the above

23)

24) Enzymes have an optimum temperature for their catalytic activity. This is best explained by the

balance between the ________ number of collisions and the ________ rate of denaturation of the

enzyme as temperatures increase.

A) decreased; decreased

B) increased; decreased

C) decreased; increased

D) increased; increased

E) none of the above

24)

25) A multi-step biochemical process in which the rate of an early step is affected by the concentration

of products of a later step is said to be subject to

A) feedback control.

B) hydrolysis.

C) decomposition.

D) pH control.

E) all of the above

25)

26) The mechanism of enzyme control that is similar to noncompetitive inhibition because both involve

interactions with the enzyme at locations other than the active site is

A) zymogen production.

B) feedback inhibition.

C) allosteric interaction.

D) zymogen activation.

E) genetic control.

26)

SHORT ANSWER. Write the word or phrase that best completes each statement or answers the question.

27) Explain the term feedback as a mechanism for control of biochemical reactions.

27)

28) Explain how an allosteric enzyme is regulated.

28)

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MULTIPLE CHOICE. Choose the one alternative that best completes the statement or answers the question.

29) When a molecule similar to the correct substrate interacts with the active site of an enzyme, the

process is called

A) competitive inhibition.

B) activation.

C) covalent modification.

D) noncompetitive inhibition.

E) irreversible inhibition.

29)

30) When a molecule other than the correct substrate interacts with some part of an enzyme to alter the

shape of the active site, the process is called

A) irreversible inhibition.

B) covalent modification.

C) activation.

D) noncompetitive inhibition.

E) competitive inhibition.

30)

31) Poisons such as heavy metal ions or insecticides can disrupt enzyme function by

A) competitive inhibition.

B) irreversible inhibition.

C) covalent modification.

D) disruption of tertiary structure.

E) all of the above

31)

32) When a metal ion such as Pb(II) interferes with the functioning of an enzyme, the most probable

mechanism is

A) genetic control.

B) feedback control.

C) reversible competitive inhibition.

D) reversible noncompetitive inhibition.

E) irreversible inhibition.

32)

33) Another term for substances that bind irreversibly with the active site of an enzyme is

A) poisons.

B) hormones.

C) coenzymes.

D) zymogens.

E) activators.

33)

34) Noncompetitive inhibition can be overcome by

A) increasing the concentration of substrate.

B) decreasing the concentration of inhibitor.

C) decreasing the concentration of products.

D) decreasing the concentration of substrate.

E) increasing the concentration of enzyme.

34)

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