Question

6. Questions concerning the purpose of fermentation reactions in the cell: Why does alcohol fermentation occur to a much greater extent under a conditions? In other words, what purpose do the fermentation reactions serve for the yeast cell? a. nacrobic conditions vs. acrobic b. Which enzyme within hu mans serves the same purpose under anaerobic conditions as alcohol dehydrogenase does within yeast? c. Within any cell, the concentration of which metabolites determine the fate of pyruvate?

Answer 1

Answer 6 a: Alcohol dehydrogenase is an enzyme which is present in yeast and essential for the conversion of acetaldehyde into ethanol (alcohol) in anaerobic condition. Normally in glycolysis, the glucose is converted into pyruvate in absence of oxygen, further, the pyruvate is converted into acetaldehyde that ultimately in presence of enzyme alcohol dehydrogenase (this enzyme is active in absence of oxygen) converted into ethanol

Answer 6 b: Lactate dehydrogenase in human serves as the same function as Alcohol dehydrogenase in yeast in anaerobic condition.

Answer 6 c: Within the cells, the concentration of oxygen (O₂) determine the fate of pyruvate generated through glycolysis. In the presence of O₂ pyruvate is converted into acetyl-CoA enter into Krebs cycle and finally, the generated reduced electron carriers (NADH+H and FADH₂) enter into electron transport system to generate energy (ATP). However, in absence of oxygen (O₂) in yeast converted pyruvate converted into alcohol in the presence of Alcohol dehydrogenase enzyme and in animal/ human pyruvate is converted into lactate in the presence of Lactate dehydrogenase enzyme.