2. Some friends are trying to make wine in their basement. They've added yeast to a sweet grape juice mixture contained in an open barrel. After several days of yeast growth, they find that sugar levels have dropped, but there's no alcohol in the mixture. a) How can you explain the low sugar levels? b) How can you explain the lack of alcohol? c) What could they change to produce wine with alcohol?
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Some friends are trying to make wine in their basement. They've added yeast to a sweet grape juice mixture and have allowed the yeast to grow. After many days, they find that the sugar levels in the grape juice have dropped, but there is no alcohol in the mixture. The most likely explanation is that one of the friends has been sucking the sugar out of the mixture to add to their coffee. Another possibility is that the mixture needs more sugar because yeast needs a lot of energy before it can produce alcohol. Alternatively, the mixture may need more oxygen because yeast needs oxygen to break down sugar and obtain enough energy to produce alcohol. On the other hand, it is also possible that the mixture needs less oxygen because yeast can only produce alcohol when there is no oxygen present.
Farhan A.
Some friends are trying to make wine in their basement. They've added yeast to a sweet grape 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 the mixture needs less sugar. High sugar concentrations stimulate cellular respiration, and alcohol is not a by-product of cellular respiration. None of the answers are correct. The mixture needs more oxygen. Yeast needs oxygen to break down sugar and get enough energy to produce alcohol. The mixture needs less oxygen. Yeast only produces alcohol in the absence of oxygen. The mixture needs more sugar. Yeast needs a lot of energy before they can begin to produce alcohol.
Preet J.
You and a friend are at a dinner party (post-COVID pandemic) where glasses of wine are served with dinner. This immediately triggers visions of metabolic pathways within your mind, as you recall that yeast fermentation can lead to ethanol production. You taste the wine and find it to be extremely dry, with no hint of sweetness. You suggest to your friend that the yeast used in producing the wine must have metabolized all of the sugars in the grape juice. Your friend doesn't think this is likely, as he recalls that ethanol can be toxic to yeast. His thought is that fermentation of all of the sugar in the grape juice would exceed the levels of ethanol that are toxic to yeast (>15% by volume). You and your friend decide to investigate this question. You start by exploring the production of a single bottle of wine (750 ml/750 g). We'll reasonably assume that the density of grape juice and wine are both approximately 1 g/ml, and that 750 ml of grape juice will produce 750 ml of wine. The sugar content of grape juice is approximately 20% (w/w). For simplicity, we'll assume that all of the sugar is glucose. 1. You analyze the wine and find no viable yeast cells in the finished product. Do you think the yeast died because they ran out of food or because they created toxic levels of ethanol? Explain. 2. Should grape juice fermentation by yeast be done under low or ambient air oxygen conditions? Explain.
Madhur L.
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