Enzyme 2

Question 1

What is the primary function of an enzyme?
A) Increase reaction equilibrium
B) Decrease the energy of reactants
C) Lower the activation energy of a reaction
D) Alter the thermodynamic stability of products

Answer 1

C

Question 2

Which catalytic strategy involves the formation of a transient covalent bond between enzyme and substrate?
A) Acid-base catalysis
B) Covalent catalysis
C) Metal ion catalysis
D) Electrostatic catalysis

Answer 2

B

Question 2

What is the name of the high-energy intermediate formed during an enzyme-catalyzed reaction?
A) Activation barrier
B) Substrate complex
C) Transition state
D) Enzyme-product complex

Answer 2

C

Question 2

Which of the following best describes the steady-state assumption in enzyme kinetics?
A) The concentration of substrate remains constant
B) The enzyme undergoes a permanent conformational change
C) The enzyme-substrate complex reaches a constant concentration
D) The reaction proceeds at the maximum rate

Answer 2

C

Question 3

In acid-base catalysis, which amino acid is most commonly involved in proton transfer?
A) Glycine
B) Histidine
C) Alanine
D) Proline

Answer 3

B

Question 4

Which of the following enzyme classes catalyzes oxidation-reduction reactions?
A) Isomerases
B) Hydrolases
C) Oxidoreductases
D) Lyases

Answer 4

C

Question 5

How does an enzyme stabilize the transition state?
A) Increasing substrate energy
B) Forming strong covalent bonds
C) Lowering the activation energy
D) Increasing reaction equilibrium

Answer 5

C

Question 6

What is the primary role of metal ions in enzyme catalysis?
A) Forming peptide bonds
B) Providing structural support
C) Stabilizing charged intermediates
D) Acting as allosteric inhibitors

Answer 6

C

Question 6

Which of the following factors affects enzyme reaction velocity?
A) pH
B) Temperature
C) Substrate concentration
D) All of the above

Answer 6

D

Question 6

The Michaelis constant (Km) is defined as the substrate concentration at which the reaction velocity is:
A) Equal to Vmax
B) Half of Vmax
C) Zero
D) At equilibrium

Answer 6

B

Question 6

The maximum velocity (Vmax) of an enzyme-catalyzed reaction occurs when:
A) The enzyme is denatured
B) The enzyme is fully saturated with substrate
C) The reaction has reached equilibrium
D) The substrate concentration is zero

Answer 6

B

Question 7

Which type of inhibition occurs when an inhibitor binds at a site other than the active site?
A) Competitive inhibition
B) Non-competitive inhibition
C) Irreversible inhibition
D) Uncompetitive inhibition

Answer 7

B

Question 8

What is the function of proteolytic activation?
A) It permanently inhibits enzymes
B) It removes regulatory proteins
C) It activates an enzyme by cleaving peptide bonds
D) It changes the enzyme’s substrate specificity

Answer 8

C

Question 9

Which statement is true for allosteric enzymes?
A) They follow Michaelis-Menten kinetics
B) They exhibit cooperative substrate binding
C) They are unaffected by inhibitors
D) They do not change conformation upon binding

Answer 9

B

Question 10

What is the function of covalent modification in enzyme regulation?
A) It alters enzyme activity through phosphorylation or acetylation
B) It permanently inhibits enzyme function
C) It denatures the enzyme
D) It removes coenzymes from the active site

Answer 10

A

Question 11

What is the initial velocity (Vo) in enzyme kinetics?
A) The reaction rate when [S] = Km
B) The maximum reaction rate
C) The reaction rate measured at the start of the reaction
D) The reaction rate at equilibrium

Answer 11

C

Question 12

What happens when [S] &laquo_space;Km?
A) The reaction follows first-order kinetics
B) The reaction follows zero-order kinetics
C) The enzyme is saturated
D) The enzyme is inactive

Answer 12

A

Question 13

What happens when [S]&raquo_space; Km?
A) The reaction follows zero-order kinetics
B) The reaction follows first-order kinetics
C) The enzyme has high affinity for the substrate
D) The reaction rate decreases

Answer 13

A

Question 13

Which graph best describes the dependence of Vo on [S] in enzyme kinetics?
A) Linear
B) Exponential
C) Hyperbolic
D) Sigmoidal

Answer 13

C

Question 13

Which enzyme kinetic model explains how enzymes catalyze reactions?
A) Lock and Key Model
B) Induced Fit Model
C) Michaelis-Menten Model
D) Allosteric Model

Answer 13

C

Question 14

What is the function of an allosteric inhibitor?
A) It permanently inactivates the enzyme
B) It prevents the enzyme from binding its substrate
C) It binds to a regulatory site and alters enzyme activity
D) It competes with the substrate at the active site

Answer 14

C

Question 15

What is the relationship between Km and enzyme-substrate affinity?
A) A higher Km means higher affinity
B) A lower Km means higher affinity
C) Km is unrelated to substrate affinity
D) Km measures enzyme inhibition

Answer 15

B

Question 16

Which of the following does NOT affect enzyme activity?
A) pH
B) Temperature
C) Substrate concentration
D) Covalent bonds within the active site

Answer 16

D

Question 17

How do enzymes affect reaction equilibrium?
A) They shift equilibrium towards the reactants
B) They shift equilibrium towards the products
C) They do not change equilibrium, only reaction speed
D) They increase the energy of reactants

Answer 17

C

Question 18

Which factor primarily determines an enzyme's catalytic efficiency? A) The concentration of enzyme alone B) The ratio of kcat to Km C) The free energy of the reaction D) The stability of the enzyme

Answer 18

B

Question 19

What is the effect of a competitive inhibitor on an enzyme-catalyzed reaction? A) It decreases Vmax B) It increases Km C) It decreases Km D) It binds at an allosteric site

Answer 19

B

Question 20

Which enzyme inhibition type is characterized by an inhibitor binding only to the enzyme-substrate complex? A) Competitive inhibition B) Non-competitive inhibition C) Uncompetitive inhibition D) Irreversible inhibition

Answer 20

C

Question 21

In non-competitive inhibition, how are Km and Vmax affected? A) Km increases, Vmax remains constant B) Km remains constant, Vmax decreases C) Both Km and Vmax decrease D) Both Km and Vmax remain constant

Answer 21

B

Question 22

Which of the following statements about irreversible inhibitors is true? A) They bind weakly and can be removed easily B) They form permanent covalent bonds with the enzyme C) They increase reaction rates D) They bind to the active site but do not affect enzyme function

Answer 22

B

Question 23

What does a Lineweaver-Burk plot represent? A) A double-reciprocal transformation of the Michaelis-Menten equation B) The effect of temperature on enzyme kinetics C) The inhibition pattern of an allosteric enzyme D) The influence of pH on enzyme structure

Answer 23

A

Question 24

Which of the following is true regarding allosteric enzymes? A) They follow Michaelis-Menten kinetics B) They exhibit sigmoidal (S-shaped) velocity vs. substrate concentration curves C) They are only regulated by covalent modifications D) They do not have regulatory binding sites

Answer 24

B

Question 25

In a metabolic pathway, the final product inhibits the first enzyme. What is this an example of? A) Covalent modification B) Feedback inhibition C) Irreversible inhibition D) Cooperativity

Answer 25

B

Question 25

A mutation in an enzyme increases Km but does not change Vmax. What does this indicate? A) The enzyme has lost all catalytic activity B) The enzyme binds substrate with lower affinity C) The enzyme undergoes allosteric regulation D) The enzyme is permanently inactivated

Answer 25

B

Question 26

What is the main function of chymotrypsin in enzymatic catalysis? A) It hydrolyzes ester bonds B) It hydrolyzes peptide bonds C) It oxidizes fatty acids D) It synthesizes DNA

Answer 26

B

Question 27

What role does phosphorylation play in enzyme regulation? A) It permanently inactivates enzymes B) It is an irreversible modification C) It acts as a reversible on/off switch for enzyme activity D) It prevents substrate binding

Answer 27

C

Question 28

Which term describes a molecule that binds to an enzyme and increases its activity? A) Inhibitor B) Allosteric activator C) Covalent modifier D) Substrate analog

Answer 28

B

Question 29

How does temperature affect enzyme activity? A) It has no effect on enzyme function B) Enzyme activity always increases with temperature C) High temperatures can denature enzymes, reducing activity D) Low temperatures permanently deactivate enzymes

Answer 29

C

Question 30

What does kcat represent in enzyme kinetics? A) The number of active sites in an enzyme B) The enzyme’s binding affinity for its substrate C) The turnover number, or the number of substrate molecules converted per second per enzyme molecule D) The inhibitor concentration needed to reduce activity by half

Answer 30

C

Question 31

Which of the following statements about the Michaelis-Menten equation is FALSE? A) It describes the relationship between enzyme activity and substrate concentration B) It assumes enzyme-substrate complex formation reaches equilibrium C) It applies only to allosteric enzymes D) It defines Km as the substrate concentration at half Vmax

Answer 31

C

Question 32

A sigmoidal enzyme activity curve is most commonly associated with which type of enzyme? A) Michaelis-Menten enzymes B) Allosteric enzymes C) Hydrolases D) Lyases

Answer 32

B