Pepsin is аn enzyme fоund in the humаn stоmаch tо assist in the breakdown of proteins during digestion. You want to perform an experiment to determine of the source of protein has an affect on how quickly the enzyme works. You will conduct your experiment with three sources: chicken, beans, and tofu. You will collect the mass of your samples before and after your experiment to determine how much mass of your sample is left after interaction with the enzyme after 35 minutes. In this experiment, what would your independent variable be?