1. the brown color, which usually develops when a potato or apple is cut or bruised, is the result of a chemical catalyzed by several enzymes. one of the most important of these enzymes is catecholase which is brought into contact with its substrate, catechol, when cells are ruptured and exposure to the o2 in air resulting in the oxidation of catechol to the brownish colored benzoquinone. this so called "wound reaction" is apparently protective since the quinones are toxic to microorganisms.

five test tubes were labeled with varying hydrogen ion concentrations expressed in molarity, [h+]. each tube was filled with 3 ml phosphate buffer at the designated [h+] and 10 drops of catechol was added to each test tube, followed by 10 drops of potato extract. each tube was stoppered and inverted many times. after a waiting period of 3 minutes it was observed that a brown substance was accumulating in the tubes.

the absorbance of each solution was measured and the fol