Kinetics of Alcohol Dehydrogenase-Catalyzed Oxidation of Ethanol Followed by Visible Spectroscopy

A two-week biochemistry experiment was introduced in the second-semester general chemistry laboratory to study the oxidation of ethanol in vitro in the presence of the enzyme alcohol dehydrogenase (ADH). This reaction should pique student interest because the same reaction also occurs in human bodies when alcoholic drinks are consumed. Procedures were developed to follow the biochemical reaction by visible spectroscopy and to avoid specialized equipment. The effect of substrate concentration on the rate of this enzymatic reaction was investigated during the first week. One of the solutions was allowed to reoxidize in air and recover the color in absence of additional ethanol to demonstrate the fact that open living systems tend to reach equilibrium with their oxidizing surroundings in the absence of an influx of energy in form of reducing agents. The effects of temperature, pH, the specificity of the enzyme to several substrates, and the enzyme's inhibition by heavy metals were explored during the second week. An anonymous voluntary survey expressed student satisfaction with the lab.