Question

Some friends are trying to make wine in their basement. Theyve added yeast to a sweet grape 36) juice mixture and have allowed the yeast to grow. After several days they find that sugar levels in the grape juice have dropped, but there's no alcohol in the mixture. The most likely explanation is that

A) the yeast used the alcohol as a carbon source.

B) the mixture needs more sugar, because yeast need a lot of energy before they can begin to produce alcohol.

C) the mixture needs more oxygen, because yeast need oxygen to break down sugar and get enough energy to produce alcohol

D) the mixture needs less oxygen, because yeast only produce alcohol in the absence of oxygen

Answer 1

D) the mixture needs less oxygen, because yeast only produce alcohol in the absence of oxygen

Step-by-step explanation:

Alcohol fermentation is incomplete oxidation of sugars in the absence of oxygen. The pathway serves as a source of ATP for some organisms. Yeast cells perform alcohol fermentation in the absence of oxygen.

Since the sugar level of the mixture dropped without any alcohol production, this means that yeast cells performed aerobic cellular respiration. Aerobic cellular respiration is the process of complete oxidation of sugars in the presence of oxygen and produces a large number of ATP molecules. To make the yeast cells to perform alcohol fermentation, the oxygen levels of the mixture should be dropped so that the yeast cells shift towards the anaerobic respiration.