Question

When yeast growing anaerobically in a 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 uncoupler 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

Hint: The realisation that unique species were involved in fermentation was further supported by Pasteur's studies on butyric acid fermentation.

Complete Answer:
- The studies led Pasteur to the surprising discovery that by moving air (that is, oxygen) through the fermenting fluid, a phenomenon known today as the Pasteur effect, the fermentation process could be halted.
- He concluded that this was because of the presence of a life-form that could operate only in the absence of oxygen.This led to his creation of aerobic and anaerobic concepts, respectively, to designate species that exist in the presence or absence of oxygen.
- In the presence of $O_2$, the Pasteur effect includes the transition from anaerobic glycolysis (fermentation) to respiration (the absorption of $O_2$) and its value lies in the fact that the cells turn to a more economical mode of energy acquisition.
- For a given substrate, during respiration as during fermentation, approximately 20 times as much energy is extracted.
- As a consequence, in the presence of $O_2$, the rate of utilisation of the substrate, for example, glucose, decreases. The struggle between respiration and adenosine diphosphate (ADP) fermentation glycolysis, which is used to form adenosine triphosphate ( ATP), is apparently the molecular mechanism of the Pasteur effect.
- The coupling between electron transport and phosphorylation reactions is inhibited by oxidative phosphorylation uncouplers in mitochondria , thereby inhibiting ATP synthesis without affecting the respiratory chain and ATP (H(+)-ATPase) synthase.

The correct Answer is option (B) Pasteur effect will remain unchanged.

Note: The first major finding by Pasteur in the vaccine research came in 1879 and involved a disease called chicken cholera. Pasteur was the first to consider virulence variability. In the study of infectious diseases, this concept is still relevant today, particularly in terms of understanding the emergence of diseases such as bovine spongiform encephalopathy (BSE), (SARS), and ( AIDS).