Question

32. Although the actual procedure is much more involved, the basic metabolism of wine-making involves inoculating grape juice with a special strain of the yeast Saccharomyces cerevisiae. S. cerevisiae will preferentially perform aerobic respiration on sugars in the juice, but it is also capable of fermenting those sugars to yield carbon dioxide and alcohol, an important component of wine. Assume you inoculate a container of juice filled almost to the top and then close the lid. What will the yeast do?

1. S. cerevisiae will grow aerobically, consume the oxygen available, and once the oxygen level gets too low, switch to fermenting the sugars to yield alcohol.
2. S. cerevisiae will grow aerobically, then switch to anaerobic respiration as the oxygen level drops.
3. S. cerevisiae will only ferment the sugars to yield alcohol.
4. S. cerevisiae will grow aerobically on the sugars, producing oxygen in the process.

Answer 1

S. cerevisiae is capable of producing ATP via aerobic respiration so when oxygen is present the S. cerevisiae produce ATP aerobic respiration as the S. cerevisiae uses the available oxygen, oxygen level in the container decreases, ( oxygen was present in the space between juice and the lid) S. cerevisiae switches to anaerobic fermentation ( alcohol fermentation) and produces ethanol. so the answer is A) S. cerevisiae will grow aerobically, consume the oxygen available, and once the oxygen level gets too low, switch to fermenting the sugars to yield alcohol.