In his studies of alcoholic fermentation by yeast, Louis Pasteur noted that the

Question

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? Estimate how much less glucose they would use compared to anerobic conditions, explaining how you made your estimate.

B. Why would DNP counteract or prevent the Pasteur effect? Write within the box. Anything outside the box will not be graded. Your answer myst be in complete, grammatical sentences.

Explanation / Answer

a) In the presence of oxygen (aerobic oxidation) glucose yields more ATP (32 moles of ATP per mole of glucose) therefore yeast cell gets more ATP (energy) from glucose under aerobic condition therefore consumes less glucose, while the opposite for anaerobic condition (2 moles of ATP per mole of glucose) therefore consumes more glucose.

b)DNP blocks ATP production (look it up for verification) under aerobic conditions; therefore even under aerobic condition the yeast cell would consume more glucose to get the same amount of ATP (when compared to without DNP present).

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