1) Which of the following best describes a metastable state?

A) The metastable state is a state of the substrate in which the reaction can proceed but typically requires a catalyst.

B) The metastable state is formed by transient complexes with the substrate.

C) This state changes the position of the equilibrium but not the rate.

D) This state is composed of the difference in activation energy of a catalyzed versus an uncatalyzed reaction.
E) The metastable state is created by the prosthetic group of the enzyme.

A

2) The work of James B. Sumner was to

A) originate the term ferments to describe enzymes.

B) crystallize urease, the first enzyme isolated.

C) prove that enzymes were carbohydrates.

D) discover ribozymes.

E) isolate the insulin hormone.

B

3) An enzyme

A) decreases the rate of a reaction.

B) is always a protein.

C) does not change the rate at which the equilibrium is achieved.

D) binds substrates in a manner that facilitates the formation of product.

E) changes the position of the equilibrium of the reaction.

D

4) The site on an enzyme that will bind the substrate is called the

A) catalyst.
B) activation site.
C) metastable site.
D) active site.
E) prosthetic group.

D

5) Which of the following is an example of a prosthetic group?

A) a nickel catalyst
B) a zinc ion
C) carboxypeptidase A
D) a glycine residue
E) a polypeptide chain

B

6) Which of the following is an enzyme?

A) histidine
B) ATP
C) iron
D) N-acetylmuramic acid
E) carboxypeptidase A

E

7) All of the following are examples of irreversible enzyme inhibitors except

A) herbicides.
B) natural poisons.
C) monoamine oxidase inhibitors.
D) aspirin.
E) pesticides.

C

8) As new enzymes are discovered, the EC system for naming enzymes is to be used. The names are to be based on which of the following criteria?

A) a description of substrate function
B) an indication of the size of the substrate
C) the six major classes of enzyme function
D) the name of the substrate
E) the size of the enzyme

A

9) The active site for carboxypeptidase

A) is formed by the interaction of two polypeptide chains.
B) involves only 6 out of a total of 307 amino acids.
C) uses iron as the prosthetic group.
D) contains a glutamate residue at position 69.
E) contains amino acids that are contiguous to one another along the primary sequence of the
protein.

B

10) According to the EC system, which is not one of the major groups of enzymes?

A) hydrolases
B) proteases
C) oxidoreductases
D) ligases
E) transferases

B

11) An enzyme is active in the stomach of an animal but quickly loses its activity when it leaves the stomach. This example illustrates that enzymes are

A) sensitive to changes in pH.
B) consumed by the quantities of substrate in the small intestine.
C) inactivated by movement.
D) specific to the organs in which they are produced.
E) inactivated by inhibitors in the small intestine.

A

12) A sick person often has a fever, which can inhibit the growth of bacteria because

A) sweating removes prosthetic groups from biological enzymes.
B) fever blocks synthesis of proteins in the bacterial nucleus.
C) bacteria reproduce more rapidly at higher body temperature.
D) the higher temperature increases the activity of lyases.
E) enzymes do not function as well at temperatures other than the optimal temperature.e

E

13) An organism that is labeled a cryophile is capable of

A) synthesizing liquid nitrogen.
B) producing large quantities of liquid hydrogen.
C) growth in hydrothermal vents.
D) growth at 4°C.
E) both choices C and D

D

14) The equation AB + H2O → A + B would be catalyzed by which of the following classes of enzymes?

A) oxidoreductases
B) isomerases
C) ligases
D) transferases
E) hydrolases

E

15) The equation A-PO4 + B → A + B-PO4 would be catalyzed by which of the following classes of
enzymes?

A) transferases
B) oxidoreductases
C) ligases
D) isomerases
E) hydrolases

A

16) Substrate activation may involve

A) accepting protons from the enzyme.
B) formation of temporary covalent bonds.
C) donation of protons to the enzyme.
D) a change in enzyme conformation induced by substrate binding.
E) all of the above

E

17) An enzyme influences the structure of which of the following?

A) substrate
B) intermediate
C) cofactor
D) product
E) transition state

E

18) A competitive inhibitor will affect the ________ of an enzymatic reaction.

A) V max
B) P
C) K m
D) S
E) b oth choices A and B

C

19) A noncompetitive inhibitor will affect the ________ of an enzymatic reaction.

A) P
B) K m
C) V max
D) S
E) both choices A and B

C

20) The type of inhibitor that binds to the enzyme (E) but not to the enzyme-substrate (ES) complex
is a(n) ________ inhibitor.

A) uncompetitive
B) competitive
C) mixed-type
D) noncompetitive
E) coenzyme

B

21) Why is the Lineweaver—Burk plot important in enzyme kinetics?

A) It makes it easier to determine Vmax.
B) It is a single-reciprocal plot.
C) It is nonlinear.
D) It illustrates enzyme specificity.
E) It reveals the presence of prosthetic groups in enzymes.

A

22) The Michaelis constant

A) is equal to the substrate concentration at Vmax/2.
B) is equal to twice the Vmax.
C) can be determined using the Lineweaver—Burk plot.
D) both choices A and C
E) choices A, B, and C

D

23) Saturation can be defined as

A) inhibition of enzyme function by blocking the active site.
B) the substrate concentration at which velocity reaches one-half maximum velocity.
C) the inability to increase reaction velocity beyond a finite upper limit.
D) acharacteristic of all uncatalyzed reactions.
E) denaturation of an enzyme.

C

24) The equation v = Vmax [S]/(Km + [S]) is part of which of the following plots?

A) Eadie—Hofstee
B) Michaelis—Menten
C) Lineweaver—Burk
D) both choices A and B
E) n one of the above

B

25) An allosteric inhibitor

A) binds at the regulatory site.
B) is converted to an activator by the enzyme.
C) is identical to the active site.
D) binds and activates the high-affinity state of the enzymes.
E) increases the rate of substrate binding.

A

26) A competitive inhibitor

A) irreversibly binds and inactivates the enzyme.
B) binds at a site other than the active site.
C) cannot be processed by the enzyme.
D) does not inhibit enzyme activity but does lower substrate concentration.
E) binds to and inactivates the substrate.

C

27) An example of an irreversible inhibitor is

A) acetylcholinesterase.
B) a competitive inhibitor.
C) isoleucine.
D) penicillin.
E) a noncompetitive inhibitor.

D

28) Covalent modification

A) can activate an enzyme.
B) can involve the addition of phosphate groups.
C) affects the activity of an enzyme by adding or removing a chemical group.
D) produces modifications that can sometimes be reversed.
E) all of the above

E

29) Which of the following is/are means whereby a catalyst can lower the activation energy of a reaction?

A) decreasing the number of reactive molecules
B) inefficient collisions
C) altering the temperature within the cell to one appropriate for reactions to proceed
D) permanently binding substrates
E) quantum tunneling

E

30) Of the following, which is used to inhibit specific enzymes in the treatment of many bacterial
and viral diseases?

A) intercalating agents
B) nitrous oxide
C) X-rays
D) substrate analogues
E) noncompetitive inhibitors

D

31) A noncompetitive inhibitor will

A) bind to free enzyme.
B) decrease Vmax.
C) decrease Km.
D) bind to free product.
E) both choices A and C

B