Investigation into the effect of a named variable on the rate of an enzyme-controlled reaction.

This website has suggestions for a variety of enzyme reactions any of which could be used to achieve the objectives of this practical.

The AQA handbook suggests the reaction of trypsin with milk proteins in which the milk slowly becomes clear. The time taken for the solution to become sufficiently clear for an ink mark to be visible through the solution is measured as an indication of the rate of the reaction. Using a colorimeter the slow clearing of the solution can be continuously monitored to obtain a more objective measure of the rate of the reaction.

We have not had very good results with trypsin and have obtained far better results using neutrase. Apart from giving better results neutrase is a liquid so easier to prepare, less expensive and with less hazard than trypsin.

Another really good method uses the reaction of dopa oxidase converting L-dopa to red dopachrome. This is an easy, cheap, safe and reliable assay with interesting features.