Enzyme Q breaks down a blue substrate to form colourless products.
Four reaction mixtures containing enzyme Q and the blue substrate were tested under the conditions shown in the table. The same volumes and concentrations of enzyme and substrate were used in every mixture. A colorimeter recorded the time taken for each mixture to reach a fixed colour reading.
The results are means from three repeats.
| pH | Temperature in ∘C^\circ\text{C}∘C | Mean time in s\text{s}s |
|---|---|---|
| 4 | 20 | 165 |
| 6 | 25 | 92 |
| 8 | 30 | 48 |
| 10 | 35 | 76 |
The student concludes that the optimum pH of enzyme Q is pH 8.
Evaluate the student's conclusion.
184 exam-style questions on OCR GCSE Biology 1.2 What happens in cells (and what do cells need)?, covering 1.2.1 Structure of DNA, 1.2.2 Nucleotides and complementary bases, 1.2.3 Protein synthesis, 1.2.4 DNA structure and the proteins made, 1.2.5 Investigating enzymatic reactions, and 1.2.6 Mechanism of enzyme action. Each one has a worked solution and a mark scheme showing where the marks go.