Lactase is an enzyme that breaks down lactose into glucose and galactose - Edexcel - GCSE Biology Combined Science - Question 4 - 2019 - Paper 1

To determine the rate of reaction for 25 beads, we use the formula:

$$ext{Rate of reaction} = \frac{\text{Change in product}}{\text{Time taken}}$$

From Figure 5, when there are 25 beads, it took 120 seconds to produce glucose. The reaction produces glucose corresponding to the number of beads used, so let's assume the change in product is '1 unit'. Thus, the rate of reaction is:

$$\text{Rate of reaction} = \frac{1 \text{ unit}}{120 \text{ seconds}} = 0.0083 \text{ s}^{-1}$$

So the answer corresponds to option A, which is 0.008 s⁻¹.