Explain5 marksStandard
An enzyme-catalysed reaction was investigated at a range of substrate concentrations, both in the absence and in the presence of a reversible inhibitor. The initial rate of reaction (μmol product min⁻¹) was measured for each substrate concentration. The results are shown in the table below.
| Substrate concentration (mmol dm⁻³) | Rate without inhibitor (μmol min⁻¹) | Rate with inhibitor (μmol min⁻¹) |
|---|---|---|
| 0.5 | 10 | 5 |
| 1.0 | 15 | 8 |
| 2.0 | 22 | 12 |
| 5.0 | 30 | 18 |
| 10.0 | 35 | 22 |
| 20.0 | 38 | 25 |
From the data, it is observed that the maximum rate (Vmax) is approximately 40 μmol min⁻¹ without inhibitor and 26 μmol min⁻¹ with inhibitor, while the Michaelis constant (Km) is approximately 2.0 mmol dm⁻³ without inhibitor and 4.0 mmol dm⁻³ with inhibitor.
Explain whether the inhibitor is competitive or non-competitive. Use the changes in Vmax and Km to support your answer.