Deck 23: Enzymes

Question 1

Which of the following is catalyzed by arginase?

A) the conversion of D-arginine to urea and D-ornithine
B) the conversion of L-arginine to urea and L-ornithine
C) the conversion of L-arginine to urea and D-arginine
D) the conversion of both the D and L forms of arginine to urea and the D and L forms of ornithine

Answer 1

B

Question 2

Which of following is true of urease?

A) It catalyzes the degradation of uracil.
B) It catalyzes the synthesis of urea.
C) It catalyzes the hydrolysis of urea.
D) It catalyzes the hydrolysis of all amines.

Answer 2

C

Question 3

Enzymes are classified into how many different major groups?

A) 4
B) 6
C) 8
D) 10

Answer 3

B

Question 4

Lactate dehydrogenase belongs to which group of enzymes?

A) hydrolases
B) lyases
C) oxidoreductases
D) transferases

Question 5

What name is given to any (organic or inorganic) nonprotein portion of an enzyme?

A) apoenzyme
B) coenzyme
C) cofactor
D) substrate

Question 6

Which of the following is true of enzymes?

A) They lower the activation energy for a chemical reaction.
B) They speed up the rate of a chemical reaction.
C) both a and b
D) neither a nor b

Question 7

What name is given to the organic cofactor of an enzyme?

A) apoenzyme
B) chaperone
C) coenzyme
D) substrate

Question 8

Which of the following is true of trypsin?

A) It does not affect any peptide bonds.
B) It hydrolyzes all peptide bonds.
C) It hydrolyzes peptide bonds to leucine and phenylalanine.
D) It hydrolyzes peptide bonds to arginine and lysine.

Question 9

The names of enzymes are often derived from which of the following?

A) the name of their discoverer
B) the compound on which they act
C) both a and b
D) neither a nor b

Question 10

Aspartate transaminase belongs to which group of enzymes?

A) hydrolases
B) lyases
C) oxidoreductases
D) transferases

Question 11

In addition to proteins, which type of molecules sometimes function as enzymes?

A) carbohydrates
B) DNA
C) lipids
D) RNA

Question 12

Tyrosine-tRNA synthetase belongs to which group of enzymes?

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

Question 13

What name is given to the molecule on which the enzyme works?

A) cofactor
B) isozyme
C) substrate
D) zymogen

Question 14

Which of the following is true?

A) All enzymes are fibrous proteins.
B) All enzymes are globular proteins.
C) The majority of enzymes are fibrous proteins.
D) The majority of enzymes are globular proteins.

Question 15

What is an apoenzyme?

A) an enzyme made entirely of protein
B) the nonprotein part of an enzyme
C) the protein only part of an enzyme
D) the inactive form of an enzyme

Question 16

Aconitase belongs to which group of enzymes?

A) hydrolases
B) lyases
C) oxidoreductases
D) transferases

Question 17

Which of the following explains why succinylcholine is used as a muscle relaxant?

A) It destroys acetylcholine esterase.
B) It is not hydrolyzed by acetylcholinesterase.
C) It is rapidly hydrolyzed by acetylcholinesterase.
D) It is slowly hydrolyzed by acetylcholinesterase.

Question 18

The names of enzymes are often derived from which of the following?

A) the reaction they catalyze
B) the compound on which they act
C) both a and b
D) neither a nor b

Question 19

Acetylcholinesterase belongs to which group of enzymes?

A) hydrolases
B) lyases
C) oxidoreductases
D) transferases

Question 20

Which of the following is true of enzymes?

A) They shift the position of a chemical equilibrium.
B) They speed up the rate of a chemical reaction.
C) both a and b
D) neither a nor b

Question 21

Which of the following is true?

A) Both competitive and noncompetitive inhibition are never reversible.
B) Both competitive and noncompetitive inhibition are sometimes reversible.
C) Only competitive inhibition is sometimes reversible.
D) Only noncompetitive inhibition is sometimes reversible.

Question 22

Noncompetitive inhibition can be often explained by which of the following models?

A) the induced fit model
B) the lock and key model
C) both a and b
D) neither a nor b

Question 23

In which type of inhibition is it not possible to restore the maximum rate of enzyme activity by adding additional substrate?

A) cooperative inhibition
B) competitive inhibition
C) noncompetitive inhibition
D) selective inhibition

Question 24

Which of the following can cause enzyme activity to either increase or decrease?

A) changing the temperature
B) increasing the substrate concentration
C) both a and b
D) neither a nor b

Question 25

Which types of amino acids interact most strongly with metal ions?

A) those with acidic side chains
B) those with basic side chains
C) those with nonpolar side chains
D) those with polar side chains

Question 26

Competitive inhibition can be explained by which of the following models?

A) the induced fit model
B) the lock and key model
C) both a and b
D) neither a nor b

Question 27

Which of the following will cause the rate of enzyme activity to increase linearly?

A) increasing the enzyme concentration
B) increasing the substrate concentration
C) increasing the temperature
D) increasing the pH

Question 28

What is the name given to a material which slows down enzyme function?

A) closer
B) inhibitor
C) isozyme
D) substrate

Question 29

In which type of inhibition does the inhibitor bind to the active site?

A) cooperative inhibition
B) competitive inhibition
C) noncompetitive inhibition
D) selective inhibition

Question 30

Which of the following is another name for a proenzyme?

A) allosteric enzyme
B) coenzyme
C) cofactor
D) zymogen

Question 31

Which of the following will the cause the rate of enzyme activity to first increase and then level off?

A) increasing the enzyme concentration
B) increasing the substrate concentration
C) increasing the temperature
D) increasing the pH

Question 32

Which of the following is the reason that trypsin is synthesized as trypsinogen?

A) It is simpler to synthesize trypsinogen.
B) Trypsinogen is a more active enzyme than trypsin.
C) Trypsin would attack the body's natural proteins.
D) Trypsin is a larger molecule than trypsinogen.

Question 33

Which of the following can cause enzyme activity to either increase or decrease?

A) changing the temperature
B) changing the pH
C) both a and b
D) neither a nor b

Question 34

What name is given to the intermediate in an enzyme-catalyzed reaction?

A) apoenzyme
B) coenzyme
C) enzyme-substrate complete
D) zymogen

Question 35

In which type of inhibition is it possible to restore the maximum rate of enzyme activity by adding additional substrate?

A) cooperative inhibition
B) competitive inhibition
C) noncompetitive inhibition
D) selective inhibition

Question 36

What is the general name used when the product of a reaction sequence inhibits an earlier step in that sequence?

A) cooperative inhibition
B) competitive inhibition
C) feedback control
D) stereospecificity

Question 37

Which of the following can cause enzyme activity to either increase or decrease?

A) increasing the substrate concentration
B) changing the pH
C) both a and b
D) neither a nor b

Question 38

Which of the following is often true of the active site of an enzyme?

A) It consists of amino acids near both the N-terminus and C-terminus.
B) It consists of amino acids which are adjacent to each other.
C) It consists of amino acids which not adjacent to each other.
D) None of the above are true.

Question 39

Which of the following is associated with noncompetitive inhibition?

A) allosterism
B) allotropism
C) isomerization
D) racemization

Question 40

In which type of inhibition does the inhibitor bind to the protein at a site other than the active site?

A) cooperative inhibition
B) competitive inhibition
C) noncompetitive inhibition
D) selective inhibition

Question 41

What disease is diagnosed by monitoring acid phosphatase activity?

A) hepatitis
B) liver cancer
C) pancreatic disease
D) prostate cancer

Question 42

Transition-state analogs do which of the following?

A) They help chemists verify the nature of the active site.
B) They inhibit enzyme activity.
C) They offer the possibility of creating designer enzymes.
D) All of the above are correct.

Question 43

Which of the following is true of all allosteric enzymes?

A) They consist of proteins only.
B) They have a nonprotein portion.
C) They have more than one active site on each subunit.
D) Binding at one site affects protein function at a second site.

Question 44

Consider the following two images depicting enzyme behavior. A B Which model provides a better explanation of noncompetitive inhibition?

A) A only
B) B only
C) Both A and B provide equally good explanations.

Question 45

Which of the following are monitored to diagnose the severity of a heart attack?

A) AST
B) CPK
C) LDH
D) all of these

Question 46

Consider the following graph for the rate of an enzyme catalyzed reaction. What would be the optimum pH for carrying out this reaction?

A) 5.0
B) 6.5
C) 7.5
D) 8.0
E) Any pH between 5.0 and 8.0.

Question 47

What term is used to describe a species which affects the functioning of an allosteric enzyme?

A) alloster
B) controller
C) inhibitor
D) regulator

Question 48

Which of the following is used in diagnosing infectious hepatitis?

A) ALT
B) CPK
C) LDH
D) PHI

Question 49

Consider the following graph for the rate of an enzyme catalyzed reaction. Approximately, what would be the optimum temperature for carrying out this reaction?

A) 20°C
B) 25°C
C) 35°C
D) 45°C
E) Any temperature between 20°C and 50°C.

Question 50

Consider the following image depicting enzyme regulation. Which of the following is depicted by this model?

A) protein modification
B) allosterism
C) competitive inhibition
D) isoenzyme action

Question 51

Transition-state analogs do which of the following?

A) They assist in the synthesis of specialized enzymes.
B) They assist in transporting the substrate to the active site.
C) They enhance enzyme activity.
D) They inhibit enzyme activity.

Question 52

Which of the following is commonly associated with protein modification?

A) phosphorylation
B) dephosphorylation
C) both a and b
D) neither a nor b

Question 53

What disease is diagnosed by monitoring amylase activity?

A) hepatitis
B) liver cancer
C) pancreatic disease
D) prostate cancer

Question 54

Consider the following two images depicting enzyme behavior. A B Which model explains competitive inhibition?

A) A only
B) B only
C) Both A and B explain competitive inhibition.

Question 55

Consider the following image depicting enzyme regulation for a two subunit enzyme. Which of the following is correct?

A) The R₀ state interacts with the substrate.
B) The R₀ state interacts with the activator.
C) The T₀ state interacts with the inhibitor.
D) All of these are correct.
E) None of these are correct.

Question 56

Consider the following image depicting enzyme behavior. Which of the following correctly characterizes the components of this model?

A) A - enzyme, B - substrate, C - active site, D - E-S complex
B) A - substrate, B - active site, C - enzyme, D - E-S complex
C) A - active site, B - substrate, C - E-S complex, D - enzyme
D) A - substrate, B - enzyme, D - E-S complex, D - active site

Question 57

What designations are used to distinguish between the two forms of an allosteric enzyme?

A) α and β
B) D and L
C) R and S
D) R and T

Question 58

An abzyme is which of the following?

A) an abnormal enzyme
B) an antibody with catalytic ability
C) an antigen with catalytic ability
D) an immunogen

Question 59

Which of the following is true of isozymes?

A) Their amino acid sequences are mirror images of one another.
B) They are a pair of enzymes which must both be present for enzyme activity to occur.
C) They are different forms of the same enzyme found in different tissues.
D) None of the above is true.

Question 60

Consider the following reaction. Which classification would be correct for the enzyme that catalyzes this reaction?

A) oxidoreductase
B) isomerase
C) transferase
D) ligase
E) hydrolase

Question 61

Examine the following graph. Which of the following explains why the "line" on the graph does not continue in a linear fashion?

A) All of the added substrate is bound to the enzyme.
B) All of the enzyme active sites are occupied.
C) The amount of enzyme present is greater than needed by the substrate.
D) An inhibitor is present.

Question 62

The following represents a transition-state in a certain reaction. Which of the following would be the best transition-state analog?

A)
B)
C)
D)