JEE Main levelSingle correct optionDifficulty 2 of 3bm120
In an enzyme-catalysed reaction with a fixed amount of enzyme, the rate is measured at increasing substrate concentration [S]. Which description is correct at the descriptive Michaelis-Menten level?
AThe rate is proportional to [S] at every concentration.
BAt low [S] the rate is nearly proportional to [S], and at very high [S] it levels off because all active sites are occupied.
CThe rate falls at high [S] because the substrate denatures the enzyme.
DThe rate is independent of [S] at low [S] and proportional to [S] at high [S].
Answer: B
When few substrate molecules are present many active sites are free, so rate rises linearly with [S]. When every active site is occupied, the enzyme is saturated and the rate reaches a plateau.