A scientist investigated the effect of an inhibitor on an enzyme-controlled reaction.She measured the initial rate of reaction at different substrate concentrations, with and without the inhibitor. The concentration of the enzyme and of the inhibitor were kept the same throughout.Her results are shown in the table.
(a) 1. The effect of the inhibitor decreases as substrate concentration increases.
2. At high substrate concentration the rate with the inhibitor approaches the rate without the inhibitor.(b) 1. The inhibitor has a similar shape to the substrate, so it is complementary to and binds to the active site.
2. Substrate cannot bind, so fewer enzyme-substrate complexes form.
| Substrate concentration / mmol dm-3 | 1 | 2 | 5 | 10 | 20 |
| Rate without inhibitor / arbitrary units | 20 | 34 | 55 | 68 | 74 |
| Rate with inhibitor / arbitrary units | 8 | 15 | 32 | 50 | 66 |
(a) 1. The effect of the inhibitor decreases as substrate concentration increases.
2. At high substrate concentration the rate with the inhibitor approaches the rate without the inhibitor.(b) 1. The inhibitor has a similar shape to the substrate, so it is complementary to and binds to the active site.
2. Substrate cannot bind, so fewer enzyme-substrate complexes form.