Question

When yeast growing anaerobically in glucose-rich-environment is exposed to oxygen in sufficient quantity, its rate of glucose utilization decreases. This phenomenon is known as the Pasteur effect. Adding an un-coupler of oxidative phosphorylation would have what effect on Pasteur effect?

• A. Pasteur effect will be enhanced
• B. Pasteur effect will remain unchanged
• C. Pasteur effect will not take place
• D. Variable effect

Answer 1

The correct option is B Pasteur effect will remain unchanged

The Pasteur effect involves the transition from anaerobic glycolysis (fermentation) to respiration (the consumption of O${}_2$) in the presence of O${}_2$, and its significance lies in the fact that the cells switch to a more economical mode of obtaining energy. For a given substrate, approximately 20 times as much energy is extracted during respiration as during fermentation. As a result, the rate of utilization of the substrate, for example, glucose, decreases in the presence of O${}_2$. The molecular mechanism of the Pasteur effect apparently consists in the competition between respiration and fermentation glycolysis for adenosine diphosphate (ADP), which is used to form adenosine triphosphate (ATP). Uncouplers of oxidative phosphorylation in mitochondria inhibit the coupling between the electron transport and phosphorylation reactions and thus inhibit ATP synthesis without affecting the respiratory chain and ATP synthase (H(+)-ATPase).

So the correct option is 'pasteur effect will remain unchanged'.