3. Trypsin is a protease enzyme used in the manufacture of food for babies - Edexcel - GCSE Biology: Combined Science - Question 3 - 2020 - Paper 1

Mashing the food increases its surface area, allowing the trypsin to access more protein molecules quickly. This leads to more efficient digestion, as the enzyme can work more effectively on a larger area of the food.

One other variable that should be controlled is the temperature at which the experiment is conducted.

This variable could be controlled by using a water bath to maintain a constant temperature throughout the experiment.

The data shows that as the pH increases from 1 to 4, the time taken to digest the food decreases, indicating that trypsin is more effective at slightly acidic pH levels. However, at pH 5 and 6, the time taken to digest the food increases significantly, suggesting that higher pH levels negatively affect trypsin's activity.

To calculate the rate of digestion at pH 1, we can use the formula:

$\text{Rate} = \frac{\text{Mass of food digested}}{\text{Time taken}}$

At pH 4, the trypsin digested 1.5 g at a rate of 0.8 g/min, which means it took:

$\frac{1.5\text{ g}}{0.8 \text{ g/min}} = 1.875\text{ minutes}$

Given that at pH 1 the time to digest is 42 minutes, the rate of digestion can be calculated as follows:

$\text{Rate at pH 1} = \frac{1.5\text{ g}}{42\text{ min}} = 0.0357 \text{ g/min}$

Thus, the answer rounded to one significant figure is 0.04 g per minute.

The difference in the rate of reaction can be attributed to the optimal functioning of the trypsin enzyme at certain pH levels. At pH 4, trypsin operates best, resulting in a faster digestion rate. Conversely, at pH 1, the enzyme is denatured or less active due to the highly acidic conditions, leading to significantly slower digestion.