The question
Name: ______________________ Date: ____________ An enzyme with and without inhibitor P (4 points)
Data table
An enzyme with and without inhibitor P
Researchers measured the initial rate of a human enzyme at six substrate concentrations, with no inhibitor and with 2 mM of inhibitor P, at 37 °C and pH 7.4. The same amount of enzyme was used in every trial.
| Substrate concentration (mM) | No inhibitor | With inhibitor P |
|---|---|---|
| 0.5 | 33.3 | 9.1 |
| 1 | 50.0 | 16.7 |
| 2 | 66.7 | 28.6 |
| 5 | 83.3 | 50.0 |
| 10 | 90.9 | 66.7 |
| 50 | 98.0 | 90.9 |
(a) Describe how the effect of inhibitor P changes as substrate concentration increases. [1 point]
(b) Calculate the rate with inhibitor P at 2 mM substrate as a percentage of the rate with no inhibitor at the same concentration. [1 point]
(c) Identify whether P is a competitive or a noncompetitive inhibitor, and support your answer with evidence from the data. [1 point]
(d) A second inhibitor, R, binds the enzyme at an allosteric site. Predict the rate at 50 mM substrate with R present compared with the rate without any inhibitor, and justify your prediction. [1 point]