Edexcel IGCSE Biology 2.13 Ph and Enzyme Function Questions

Practise how pH affects enzyme activity by interpreting results and explaining active-site changes in examples such as urease, gelatine digestion and fruit browning.

Exam points

Identify the optimum pH and interpret how changing pH alters measured enzyme activity.
Explain how non-optimal pH changes an enzyme's active site and reduces substrate binding.
Apply pH effects to urease activity, gelatine digestion, fruit browning or vinegar preservation.

[Maximum number: 3]

Pineapple juice contains a protease called bromelain.
A student uses this method to investigate the digestion of solid gelatine protein by bromelain.
- place solid gelatine protein into a test tube up to a height of 5 cm
- mix $5 \mathrm{~cm}^{3}$ pineapple juice with $1 \mathrm{~cm}^{3}$ of pH 4 buffer
- place $1 \mathrm{~cm}^{3}$ of the pineapple juice and buffer solution on top of the gelatine
- leave for one hour in a water bath set to $37^{\circ} \mathrm{C}$
- measure the height of the solid gelatine and use it to calculate the volume of gelatine that has been digested

Repeat the method three more times.
The diagram shows part of the student's method.

Figure for Question Edexcel IGCSE Biology 2.13 Ph and Enzyme Function Questions question 1 — Edexcel IGCSE Biology

The student repeats the investigation with different pH buffers.

The table shows their results.

Table for Question Edexcel IGCSE Biology 2.13 Ph and Enzyme Function Questions question 1 — Edexcel IGCSE Biology

Explain the effect of changing the pH on the mean volume of gelatine digested.

All question bank results loaded

Edexcel IGCSE Biology 2.13 Ph and Enzyme Function Questions question 1