Paper 4 · November 2003 · Enzymes
In this investigation, catalase activity was tested in buffer solutions at pH3, 4, 5, 6, 7 and 8, so that the rate of the reaction could be compared across the different pH values. State why buffer solutions, rather than plain solutions of acid or alkali, were necessary for this investigation.
Model answer
buffers keep the pH constant
Also accepted: buffers maintain a constant pH, to keep the pH constant/prevent it changing during the reaction, to keep the pH constant throughout the test, keep pH constant
Explanation
A buffer resists changes in pH, so it keeps the pH constant throughout each test, making the rate at each pH value a fair comparison.
Derived from ZIMSEC Biology 9190/4 Paper 4 (Practical Test), November 2003, Q1