Question

all parts please

In his studies of alcoholic fermentation by yeast, Louis Pasteur noted that the sudden addition of oxygen (O) 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. (10 pts) 5. A) B) C) Why would the yeast cells consume less glucose in the presence of oxygen? Can you estimate how much less glucose they would use? Why would DNP counteract or prevent the Pasteur effect?

Answer 1

A) Under anaerobic conditions, only 2 ATP are produced per glucose. Thus, to get the same amount of ATP, a cell needs to use 19 times more glucose anaerobically. Under anaerobic conditions, the rate of glucose metabolism is faster, but the amount of ATP produced is smaller.

B) The processes used in alcohol production are commonly maintained in a low oxygen condition, under a blanket of carbon dioxide, while breeding yeast for biomass is done in aerobic conditions, the broth being aerated.

C) DNP blocks the principal path of aerobic ATP production, aerobic cells in the presence of DNP need about the same amount of glucose as anaerobic cells.