All A-level exam boards expect you to do an experiment that measures the rate of action of an enzyme. An enzyme is a protein that acts as a catalyst for a biochemical reaction, increasing the rate of the reaction but remaining unchanged itself. Enzyme rate experiments provide opportunities to explore how enzyme activity changes in different conditions, but the data obtained are often variable, and sometimes the answers are not intuitive (see Box 1). Why, then, would a required practical include a set of experiments about a complex area that may provide data that are not absolutely clear?
You perform the pink milk experiment described in the text using Jersey milk (5.1% fat) and commonly available whole milk (3.9% fat). In your 5 cm3 aliquots you therefore have 0.255 g and 0.195 g of fat respectively. Which lipase-treated milk decolourises phenolphthalein faster?
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