NEETBotanyBiomolecules (B)
Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R). Assertion (A): In an enzyme-catalysed reaction, the velocity ultimately reaches a maximum value ( V_ max ) which is not exceeded by any further rise in substrate concentration. Reason (R): At high substrate concentrations, there are no free substrate molecules left to bind with the active sites of the enzyme. In
Options
- ABoth (A) and (R) are correct and (R) is the correct explanation of (A)
- BBoth (A) and (R) are correct but (R) is not the correct explanation of (A)
- C(A) is correct but (R) is not correct
- D(A) is not correct but (R) is correct
Correct answer
C. (A) is correct but (R) is not correct
Step-by-step solution
Assertion (A) is correct because the velocity of an enzyme-catalysed reaction rises initially with an increase in substrate concentration and then levels off at a maximum velocity ( V_ max ). Reason (R) is incorrect. The plateau occurs because enzyme molecules are typically fewer in number than substrate molecules. At high substrate concentrations, all the active sites of the enzyme are saturated. Therefore, there are no free enzyme molecules (not substrate molecules) left to bind with the additional substrate mole