Imagine that you are in a class working on an enzyme lab. In the lab you are looking at the effect of lactase on lactose. Lactase is an enzyme that...

Imagine that you are in a class working on an enzyme lab.  In the lab you are looking at the effect of lactase on lactose.  Lactase is an enzyme that breaks apart the milk sugar lactose.  During the lab you put some lactase in a sample of milk.  You then analyze the milk for the presence of lactose at a number of time intervals.  When you are done your lab partner says that you should put the remaining milk with lactase back in the jug of milk, so that there is more milk for the next lab.  You stop your lab partner and tell them putting the sample back is not a good idea.  Why is this not a good idea?  Be sure your answer relates to enzyme activity