Paper 4 · November 2004 · Enzymes
Starch solutions A, B and C were hydrolysed for 30 minutes by the same enzyme solution P, then tested for reducing sugar. Tube A (highest original starch concentration) produced the most reducing sugar; tube B (lowest original starch concentration) produced the least. Why does a solution with a higher original starch concentration produce more reducing sugar in the same fixed reaction time?
AA higher substrate concentration lowers the activation energy needed for hydrolysis.
BA higher substrate concentration increases the optimum temperature of the enzyme.
CA higher substrate concentration reduces the amount of enzyme needed to complete the reaction.
DA higher substrate concentration increases the rate of enzyme-substrate complex formation, so the enzyme converts more substrate to product in the same time.
Explanation
More substrate molecules increase the collision (and so enzyme-substrate complex formation) rate, raising the rate of reaction and so the amount of product formed in a fixed time; the enzyme's activation energy and optimum temperature are unaffected by substrate concentration.
Derived from ZIMSEC Biology 9190/4 Paper 4, November 2004, Q1