Why did the yeast rise?
First, the glucose is reduced by anaerobic fermentation to ethanol and carbon dioxide. The yeast uses the produced energy for a fast growth and division (1). As soon as all glucose is consumed the metabolism of the yeast changes from anerobic fermentation to aerobic respiration (oxygen is required). This is called diauxic shift. During this time the yeast stops growing (2). After this shift the yeast further reduces the ethanol to carbon dioxide and water. The generated energy is used for the second growth phase (3).
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Vanessa