In His Studies of Alcoholic Fermentation by Yeast, Louis Pasteur

Essay

In his studies of alcoholic fermentation by yeast, Louis Pasteur noted that the sudden addition of oxygen (O₂) to a previously anaerobic culture of fermenting grape juice resulted in a dramatic decrease in the rate of glucose consumption. This "Pasteur effect" can be counteracted by the addition of 2,4-dinitrophenol (DNP), an uncoupler of oxidative phosphorylation. (a) Why would the yeast cells consume less glucose in the presence of oxygen? Can you estimate how much less glucose they would use? (b) Why would DNP counteract or prevent the Pasteur effect?