Multiple Choice Questions on Enzyme Inhibition

26. Which of the statement is true regarding Km
a) It is the measure of the stability of the ES complex
b) It is the measure of the stability of the affinity of an enzyme for its substrate
c) A high Km indicates weak substrate binding
d) all of these

27. Any molecule which acts directly on an enzyme to lower its catalytic rate is called
a) Regulator
b) Repressor
c) Inhibitor
d) Moderator

28. Which of the following statements are true regarding enzyme inhibition?
a) It may be reversible or irreversible
b) Reversible can be competitive or non-competitive
c) both a and b
d) it is always reversible

29. Succinate is the substrate for succinate dehydrogenase that converts succinate to fumarate. In the presence of reversible competitive inhibitor like malonate in place of succinate, the enzymes


a) K_m increases and V_max remains the same
b) both K_m and V _max increases
c) both K_m and V_max decreases
d) K_m decreases and V _max remains the same

30. Irreversible inhibitors often form covalent bonds with
a) any amino acid residues at or near the active site
b) Tryptophan and phenylalanine residues at or near the active site
c) positively charged residues at or near the active site
d) Ser or Cys residues at or near the active site


31. A reversible non-competitive inhibitor binds reversibly at a site other than the active site. This binding lead to

a) increase in K_m and V_max remains constant
b) increase in V_max and K_m remains constant
c) decrease in V_max and K_m remains constant
d) no change in V_max and K_m


32. Which of the following is an example for irreversible inhibitor
a) Di-isopropylphosphofluoridate (DIPF) with the enzyme acetylcholineesterase, involved in nerve impulse transmission
b) Penicillin with glycopeptides transpeptidase enzyme involved in bacterial cell wall synthesis
c) Iodoacetamide, a cys residue modifier at the active sites
d) all of these

33. The effect of a reversible competitive inhibitor can be nullified by
a) increasing the product concentration
b) increasing the substrate concentration
c) increasing the temperature
d) none of these

34. The action of pepstatin on the enzyme rennin is an example of
a) competitive inhibition
b) reversible competitive inhibition
c) reversible non-competitive inhibition
d) irreversible inhibition

35. Enzymes are chemically
a) Proteins
b) Proteins and nucleic acids
c) Proteins and rarely ribonucleic acids
d) Proteins and rarely carbohydrates

Learn More:
· Multiple Choice Question on Enzymes
· Multiple Choice Question on Enzymes
· Multiple Choice Question on Protein Function
· Multiple Choice Question on Protein Purification

Answers:
26. d) all of these
27. c) Inhibitor
28. c) both a and b
29. a) K_m increases and V_max remains the same
30. d) Ser or Cys residues at or near the active site
31. c) decrease in V_max and K_m remains constant
32. d) all of these
33. b) increasing the substrate concentration
34. c) reversible non-competitive inhibition
35. c) Proteins and rarely ribonucleic acids