JEE Advanced levelSingle correct optionDifficulty 3 of 3el028
Drug A binds the active-site serine of an enzyme through a covalent bond. Drug B binds the same site through hydrogen bonds and van der Waals forces. Which comparison is correct?
AInhibition by A is removed by dialysis, but inhibition by B is not
BInhibition by both A and B is removed equally easily by dilution
CInhibition by B is permanent, and inhibition by A is short-lived
DEnzyme activity blocked by A returns only when the cell makes new enzyme, whereas inhibition by B is lost when B is cleared or diluted away
Answer: D
Covalent bonds are strong and not broken under cell conditions, so the blocked enzyme molecule stays inactive and is replaced only by synthesis. Weak interactions are reversible and the drug leaves as its concentration falls.