Describe the effect of pH on the enzyme by comparing the volumes and appearance of the filtered juice in measuring cylinders B and D. State two variables that were controlled in this investigation. Suggest two ways in which you could change this investigation to make the results more accurate.

Buffer X has a pH of 4, and buffer Y has a pH of 8.

• Volume for B (with enzyme and buffer X, pH 4) is $19 \text{ cm}^3$.
• Volume for D (with enzyme and buffer Y, pH 8) is $11 \text{ cm}^3$.

• The volume of filtered juice in cylinder B ($19 \text{ cm}^3$) is greater than in cylinder D ($11 \text{ cm}^3$). This indicates that the enzyme was more active at pH 4 (buffer X) than at pH 8 (buffer Y), as more juice was produced.
• Therefore, the enzyme works better at pH 4, which is closer to its optimum pH for breaking down the fruit pulp.

2. (f) (i)

• The volume of fruit pulp was $25 \text{ cm}^3$ in all cups.
• The volume of buffer (X or Y) was $5 \text{ cm}^3$ in all cups.
• The volume of enzyme solution (or water for control) was $2 \text{ cm}^3$ in all cups.
• The temperature was kept constant (implied by the setup, usually experiments are done at room temperature or controlled temperature).
• The type of fruit used was the same.
• The time allowed for the enzyme reaction was the same for all cups.

1. Volume of fruit pulp (or type of fruit)
2. Volume of enzyme solution (or water)

2. (f) (ii)

• Repeat the experiment multiple times and calculate an average to reduce the impact of random errors.
• Use more precise measuring equipment (e.g., burettes or pipettes instead of measuring cylinders for smaller volumes).
• Use a wider range of pH values with smaller intervals to pinpoint the optimum pH more accurately.
• Maintain a more constant temperature using a water bath.
• Ensure thorough mixing of contents in each cup.

1. Repeat the experiment multiple times and calculate an average.
2. Use a water bath to maintain a constant and precise temperature.