JEE Advanced levelSingle correct optionDifficulty 3 of 3bm130
For an enzyme-catalysed reaction with fixed enzyme concentration, the initial rate was 5μMs−1 at [S]=0.1mM, 10μMs−1 at [S]=0.2mM, 98μMs−1 at [S]=20mM and 99μMs−1 at [S]=40mM. The order of the reaction with respect to substrate is
Aabout zero at low [S] and about one at high [S]
Babout one at both low and high [S]
Cabout two at low [S] and zero at high [S]
Dabout one at low [S] and about zero at high [S]
Answer: D
Doubling [S] from 0.1 to 0.2 mM doubles the rate (5 to 10), which is first order. Doubling from 20 to 40 mM raises the rate only from 98 to 99, so the enzyme is saturated and the order is nearly zero.