4 (a) Why are enzymes called biological catalysts? A because they slow down biological processes B because they speed up biological processes C because they denature biological processes D because they stop biological processes (b) Many cells contain an enzyme called catalase - Edexcel - GCSE Biology Combined Science - Question 4 - 2021 - Paper 1

Temperature should be controlled in this investigation because enzymes have an optimal temperature at which they function best. If the temperature is too low, enzyme activity decreases and the time taken to produce 20 cm³ of oxygen increases. Conversely, if the temperature is too high, enzymes can become denatured, leading to a loss of activity. Therefore, maintaining a consistent temperature is crucial for obtaining accurate and reliable results.

To plot the graph accurately, ensure that all five points corresponding to the concentrations of hydrogen peroxide and the time taken to produce 20 cm³ of oxygen are plotted. Connect these points with a smooth line to show the trend in the data.

The trend shown in the graph indicates that the time taken to collect 20 cm³ of oxygen decreases as hydrogen peroxide concentration increases. For example, at a concentration of 4 arbitrary units of hydrogen peroxide, the time taken is 32 seconds, while at 20 arbitrary units, the time taken is only 6 seconds. This suggests a negative correlation between concentration and time taken, highlighting that higher concentrations of hydrogen peroxide result in faster oxygen production.