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

Controlling the temperature is essential because enzymes have an optimum temperature at which they function best. Variations in temperature can affect the rate of enzyme activity, thus impacting the time taken to produce 20 cm³ of oxygen. If the temperature exceeds or falls below the optimum range, the enzyme could become denatured or less active, leading to inconsistent results.

All 4 points plotted accurately (± half a small square). A smooth curve or dot-to-dot line drawn to connect the points.

The time taken to collect 20 cm³ of oxygen decreases as hydrogen peroxide concentration increases, indicating a negative correlation. Initially, the curve decreases sharply, and then it flattens, suggesting that at higher concentrations, the increase in reaction rate becomes less pronounced. For instance, the time taken reduces from 32 seconds at a concentration of 4 to just 6 seconds at a concentration of 20.