Deck 22: Enzymes

Question 1

Aconitase belongs to which group of enzymes?

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

Answer 1

B

Question 2

Which of the following statements is true of enzymes?

A) They shift the position of chemical equilibrium.
B) They increase the rate of a chemical reaction.
C) They shift the position of chemical equilibrium and they increase the rate of a chemical reaction.
D) None of these

Answer 2

B

Question 3

Which of the following body fluid samples is used to diagnose the severity of a heart attack?

A) cerebrospinal fluid
B) serum
C) sweat
D) semen

Answer 3

B

Question 4

Tyrosine-tRNA synthetase belongs to which group of enzymes?

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

Question 5

According to the types of reactions that enzymes catalyze, into how many groups are enzymes classified?

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

Question 6

Which of following statements 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.

Question 7

How many subunits does lactate dehydrogenase contain?

A) 4
B) 2
C) 10
D) 6

Question 8

Which of the following statements is true of trypsin?

A) It does not affect any peptide bond.
B) It hydrolyzes all peptide bonds.
C) It hydrolyzes peptide bonds only on the carboxyl side of leucine and phenylalanine residues.
D) It hydrolyzes peptide bonds only on the carboxyl side of arginine and lysine residues.

Question 9

Aspartate transaminase belongs to which group of enzymes?

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

Question 10

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

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

Question 11

Which of the following processes is catalyzed by arginase?

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

Question 12

Acetylcholinesterase belongs to which group of enzymes?

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

Question 13

Which of the following enzymes is assayed to diagnose liver or bone disease?

A) alkaline phosphatase
B) alkaline aminotransferase
C) acid phosphatase
D) lactate dehydrogenase

Question 14

What name is given to a molecule on which an enzyme works?

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

Question 15

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) the reaction they catalyze and the compound on which they act
D) none of these

Question 16

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

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

Question 17

Lactate dehydrogenase belongs to which group of enzymes?

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

Question 18

Which of the following terms refers to nonprotein parts of enzymes that are necessary for catalytic function?

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

Question 19

Which of the following statements is true of enzymes?

A) They lower the activation energy of a chemical reaction.
B) They are extremely specific.
C) They lower the activation energy of a chemical reaction and they are extremely specific.
D) None of these

Question 20

Which of the following statements is true of enzymes?

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 21

Where is the enzyme arginase produced in the human body?

A) the liver
B) the pancreas
C) the small intestine
D) the stomach

Question 22

Which term is used for an enzyme regulation process where the formation of a product inhibits an earlier reaction in the sequence?

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

Question 23

Which of the following statements is true of chymotrypsinogen?

A) It is the active form of trypsinogen.
B) It consists of a single polypeptide chain that is 100 residues long.
C) It is formed in the pancreas.
D) It has 20 disulfide bonds.

Question 24

Which of the following statements is true of noncompetitive inhibitors?

A) They slow down the rate of reaction.
B) They increase the efficiency of an enzyme.
C) They have no effect on the shape of the enzyme.
D) They increase the activity of an enzyme.

Question 25

Which of the following changes gives a saturation curve for the rate of enzyme activity?

A) an increase in enzyme concentration
B) an increase in substrate concentration
C) an increase in temperature
D) an increase in pH

Question 26

Which of the following is another name for a proenzyme?

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

Question 27

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) induced-fit inhibition
D) irreversible inhibition

Question 28

Which of the following is an intermediate in an enzyme-catalyzed reaction?

A) an apoenzyme
B) a coenzyme-substrate complex
C) an enzyme-substrate complex
D) a zymogen

Question 29

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) induced-fit inhibition
D) irreversible inhibition

Question 30

What is the optimum pH range for the activity of the enzyme pepsin?

A) 1.5-2.0
B) 6.7-7.0
C) 3.5-4.5
D) 8.8-9.2

Question 31

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

A) a change in temperature
B) an increase in substrate concentration
C) a change in temperature and an increase in substrate concentation
D) none of these

Question 32

For which of the following reasons is trypsin synthesized as trypsinogen?

A) Trypsin can damage the small intestine.
B) Trypsinogen is a more active enzyme than trypsin.
C) Trypsin can damage the pancreas.
D) Trypsin is a larger molecule than trypsinogen.

Question 33

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

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

Question 34

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

A) an increase in enzyme concentration
B) a change in the pH
C) an increase in the enzyme concentration and a change in the pH
D) none of these

Question 35

Identify a proenzyme.

A) trypsinogen
B) pyruvate kinase
C) lactate dehydrogenase
D) pepsin

Question 36

Which of the following enzymes is an example of a lyase?

A) aconitase
B) acetylcholinesterase
C) aspartate transaminase
D) lactate dehydrogenase

Question 37

Which of the following statements is true of inhibition?

A) Both competitive and noncompetitive inhibition are irreversible.
B) Both competitive and noncompetitive inhibition are always reversible.
C) Competitive inhibition is always irreversible.
D) Noncompetitive inhibition is never reversible.

Question 38

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

A) an increase in enzyme concentration
B) an increase in substrate concentration
C) an increase in temperature
D) an increase in pH

Question 39

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

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

Question 40

Which of the following types of molecules reduce the activity of an enzyme?

A) zymogens
B) inhibitors
C) isozymes
D) substrates

Question 41

An enzyme in an inactive form that can become active after undergoing a chemical change is known as a(n) _____.

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

Question 42

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 43

Identify the optimum pH for the activity of the enzyme lactase.

A) 2.0
B) 9.0
C) 10.0
D) 6.0

Question 44

Which disease is diagnosed by assaying amylase activity?

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

Question 45

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) feedback control

Question 46

Consider the following reaction. Which group of enzymes catalyzes this reaction?

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

Question 47

Consider the following two images depicting enzyme behavior. Which image provides a better explanation for the induced-fit model?

A) A only
B) B only
C) Both A and B

Question 48

Which of the following enzymes is assayed to diagnose the severity of a heart attack?

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

Question 49

Consider the following graph for the rate of an enzyme catalyzed reaction. What is the approximate optimum temperature for carrying out this reaction?

A) 20°C
B) 25°C
C) 35°C
D) 45°C

Question 50

Which term refers to a species that can reversibly bind to an allosteric enzyme?

A) a zymogen
B) an isozyme
C) a cofactor
D) a regulator

Question 51

Which of the following statements is true of isozymes?

A) They are two different enzymes that have the same function.
B) They are a pair of enzymes that must both be present for enzyme inhibition.
C) They are different forms of the same enzyme produced in different tissues.
D) None of these are true.

Question 52

Which disease is diagnosed by assaying acid phosphatase activity?

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

Question 53

Which of the following enzymes does not consist of proteins?

A) ribozyme
B) aconitase
C) lactase
D) pepsin

Question 54

Which of the following statements is true of carbonic anhydrase?

A) It assists in the synthesis of specialized enzymes.
B) It helps catalyze protein splitting in the blood.
C) It is inhibited by acetazolamide.
D) It catalyzes the hydrolysis of urea.

Question 55

Which of the following statements is true of allosteric enzymes?

A) They always consist 006Ff one polypeptide chain or subunit.
B) They have a nonprotein portion.
C) They have more than one active site on each subunit.
D) The active site and regulatory site can be present on the same subunit.

Question 56

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

A) A only
B) B only
C) Both A and B

Question 57

Consider the following graph for the rate of an enzyme-catalyzed reaction. What is the approximate 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 58

Which of the following enzymes is assayed to diagnose infectious hepatitis?

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

Question 59

Which of the following processes is commonly associated with protein modification?

A) phosphorylation
B) positive modulation
C) phosphorylation and positive modulation
D) none of these

Question 60

Which of the following reactions is catalyzed by a hydrolase?

A) the conversion of lactate to pyruvate
B) the conversion of aspartate to glutamate and oxaloacetate
C) the conversion of acetylcholine to acetic acid and choline
D) the conversion of aconitate to isocitrate

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

Identify the optimum pH for the activity of the enzyme lipase.

A) 8.0
B) 6.0
C) 9.7
D) 2.0