Enzymes and Kinetics Questions and Answers

Multiple Choice Questions (MCQ) and Answers on Enzymes and Kinetics

Question.1: In competitive inhibition a factor is obtained from the measurement of

  1. Vmax
  2. KM
  3. Y-intercept in Lineweaver-Burk Plot
  4. None of these

Answer: 2

Question.2: Which of these proteases is not a cysteine active site protease?

  1. Calpain
  2. Cathepsin D
  3. Papain
  4. None of the above

Answer: 2

Question.3: Given an enzyme with a Km = 10m M and Vmax = 100 m mol/min. If [S] = 100 m M, which of the following will be true?

  1. A 10 fold increase in Vmax would increase velocity 10 fold y
  2. A 10 fold decrease in Km would increase velocity
  3. Both (a) and (b)
  4. A 10 fold increase in Vmax would decrease velocity 20 fold

Answer: 1

Question.4: Which of the following statements is true for enzymatically catalyzed reaction?

  1. The activation energy of the reaction is lowered so that a larger proportion of the substrate qualifies to overcome it
  2. Additional substrate molecules are energized to overcome the activation energy of the reaction
  3. The activation energy of the reaction is increased, thus decreasing the likelihood that any substrate molecules will overcome it
  4. The activation energy of the reaction is lowered so that a fewer substrate molecules can overcome it

Answer: 1

Question.5: The reciprocal equation for non competitive inhibition can be arranged to the equation for the

  1. Dixon plot
  2. Woolf-Augusteinsson-Hofstee plot
  3. Eadie-Scatchard plot
  4. Hanes-Woolf plot

Answer: 1

Question.6: The relationship between Keq, Km and Vmax is known as

  1. Haldane equation
  2. Michaelis Menten equation
  3. Numerical solution approach
  4. Gibbs-Helmholtz equation

Answer: 1

Question.7: A competitive inhibitor of an enzyme is usually

  1. a highly reactive compound
  2. a metal ion such as Hg2+ or Pb2+
  3. structurally similar to the substrate.
  4. water insoluble

Answer: 3

Question.8: Linear inhibition is sometimes called as

  1. complete inhibition
  2. incomplete inhibtion
  3. partial inhibition
  4. mixed inhibition

Answer: 1

Question.9: The types of inhibition pattern based on Michaelis Menten equation are

  1. competitive
  2. non-competitive
  3. uncompetitive
  4. all of the above

Answer: 4

Question.10: The rate-determining step of Michaelis Menten kinetics is

  1. the complex formation step
  2. the complex dissociation step to produce product
  3. the product formation step
  4. Both (a)and(c)

Answer: 2

Question.11: The effect of non-competitive inhibition on a Lineweaver-Burk Plot is that

  1. it can move the entire curve to the right
  2. it can change the y-intercept
  3. it can change the x-intercept
  4. all of these

Answer: 2

Question.12: The active site of an enzyme remains

  1. at the center of globular proteins
  2. rigid and does not change shape
  3. complementary to the rest of the molecule
  4. none of the above

Answer: 4

Question.13: The conformational change in an enzyme after the substrate is bound that allows the chemical reaction to proceed, can be explained by

  1. induced fit
  2. transition
  3. fit and fine
  4. Pasteur

Answer: 1

Question.14: The Woolf-Augusteinsson-Hofstee plot of ν versus ν/[S] and the Eadie-Scatchard plot of ν/[S] versus ν do not involve reciprocals of ν therefore are considered to be more reliable when the error in v is

  1. non-significant
  2. significant
  3. nothing to do with the reliability
  4. non significant in selected cases

Answer: 2

Question.15: Which category of enzymes belongs to class two in the international classification?

  1. Hydrolases
  2. Ligases
  3. Transferases
  4. Isomerase

Answer: 3

Question.16: Non-competitive inhibitor of an enzyme catalyzed reaction

  1. decreases Vmax
  2. binds to Michaelis complex (ES)
  3. both (a) and (b)
  4. can actually increase reaction velocity in rare cases

Answer: 3

Question.17: Which of the following statements is not true?

  1. Enzymes are proteins that bind to specific substrates and increase the velocity of reactions involving those substrates
  2. Enzymes function by overcoming the activation energy barrier of a reaction
  3. Enzymes make thermodynamically favorable reactions to proceed; they cannot make unfavorable reactions to occur
  4. Enzymes only function when they are in intact cells

Answer: 4

Question.18: Which of the following common drugs is not a specific enzyme inhibitor?

  1. Iodine
  2. Methotrexate
  3. Sulfbnilamide
  4. Penicillin

Answer: 1

Question.19: The enzyme inhibition can occur by

  1. reversible inhibitors
  2. irreversible inhibitors
  3. Both (a) and (b)
  4. None of these

Answer: 3

Question.20: In a Lineweaver-Burk Plot, competitive inhibitor shows which of the following effect?

  1. It moves the entire curve to right
  2. It moves the entire curve to left
  3. It changes the x-intercept
  4. It has no effect on the slope

Answer: 3

Question.21: Which of these enzymes contains a Zinc (Zn) ion?

  1. Carboxypeptidase A
  2. Phosphorylase B kinase
  3. Tyrosine hydroxylase
  4. Phosphodiesterase

Answer: 1

Question.22: Quasi steady state is also known as

  1. Michaelis Menten approach
  2. Briggs-Haldane approach
  3. Pseudo steady state
  4. all of the above

Answer: 3

Question.23: An enzyme and a reactant molecule maintain relationship as

  1. a temporary association
  2. an association stabilized by a covalent bond
  3. one in which the enzyme is changed permanently
  4. non complementary binding

Answer: 1

Question.24: An enzyme is assayed at an initial substrate concentration of 2 x 10-5M. In 6 minute, half of the substrate is used. The Km for the substrate is 2 x 10-3M. The value of k in minute is

  1. 0.115
  2. 0.42
  3. 0.093
  4. 6.693

Answer: 1

Question.25: The plot commonly used for determining the value of Vmax is

  1. Lineweaver Burk plot
  2. Langmuir plot
  3. Eadie Hofstee plot
  4. all of these

Answer: 4

Question.26: Which graphical method is used to determine an enzyme degree of cooperativity?

  1. Hill plot
  2. Koshland curve
  3. Michaelis-Menten hyperbola
  4. Can not be determined

Answer: 1

Question.27: A classical uncompetitive inhibitor is a compound that binds

  1. reversibly to the enzyme substrate complex yielding an inactive ESI complex
  2. irreversibly to the enzyme substrate complex yielding an inactive ESI complex
  3. reversibly to the enzyme substrate complex yielding an active ESI complex
  4. irreversibly to the enzyme substrate complex yielding an active ESI complex

Answer: 1

Question.28: A noncompetitive inhibitor of an enzyme-catalyzed reaction

  1. increases KM and increases Vmax
  2. increases KM and reduces Vmax
  3. reduces KM and increases Vmax
  4. reduces KM and reduces Vmax

Answer: 2

Question.29: An allosteric inhibitor of an enzyme usually

  1. participates in feedback regulation
  2. denatures the enzyme
  3. is a hydrophobic compound
  4. causes the enzyme to work faster

Answer: 1

Question.30: Which of the following activity is possible by transferases?

  1. Transfer of methyl groups
  2. Transfer of glycosyl group
  3. Both (a) and (b)
  4. None of these

Answer: 3