In Exercise 4, you learned about a reaction that amylase cat…

In Exercise 4, you learned about a reaction that amylase catalyzes. Below, is an example of another enzyme-catalyzed reaction.    Lactase, is an enzyme found in the human body, which is responsible for breaking down lactose molecules. Lactose molecules are found in milk products. Many people are deficient in lactase, which makes them unable to effectively break down milk products. There is a specialized test that can be done to test for lactose deficiency, using blood glucose levels as the indicator. A scientist set up an experiment to test the effect of time on lactose breakdown through this enzyme-catalyzed reaction. In this experiment, the subjects consumed 1 cup of milk, and had their blood drawn every 15 minutes to test their blood glucose level. Give an example of a variable that must be held constant in this experiment.