Plant cells contain enzymes that catalyse metabolic reactions. Some of these enzymes catalyse the release of oxygen from hydrogen peroxide. A plant extract solution can be produced which will contain these enzymes. When hydrogen peroxide and a plant extract solution are mixed oxygen is released. The oxygen forms bubbles that make a foam on the surface. You are required to investigate the effect of pH on the progress of the enzyme-catalysed reactions by: • changing the pH (independent variable) using buffers • measuring the height of the foam (dependent variable) produced by the release of oxygen. To follow the progress of this reaction you will need to measure the height of foam at different times for a total of 3 minutes.