<prompt> In an enzyme mediated reaction, substrate concentration was 1000 times Km 1 of substrate is metabolised to form 12 mmol of substrate in 9 minutes. If in the same reaction enzyme concentration is reduced to 13rd and substrate concentration is doubled. How much time is needed to produce same amount of product?9 min13.5 min18 min27 min  <response>: Ans. D. 27 minWe can consider this question in two partsFirst part1000Km 12mmol of substrate in 9 minutesWhen SKm in a hyperbolic curve it follow 1st order kinetics i.e. is directly proportion to velocity of reaction. But here its 1000Km means its zero order kinetics, i.e. even if increased velocity do not increase.Second partEnzyme concentration E is 13 of initial E concentrationE is directly proportional to velocity of reactionis2000Km So this is zero order kinetics hence velocity of reaction depends only EE13E, hence New Velocity V is 13 V initialHence time taken is three times more than initial time takenTime9x327min 