Final answer:
Yeasts are facultative anaerobes that can switch to alcohol fermentation in the absence of oxygen to generate energy. This process is used in wine and beer production, as well as in baking to make dough rise.
Step-by-step explanation:
Yeasts are facultative anaerobes, which means they can grow with or without oxygen. When oxygen is present, yeasts prefer to use aerobic respiration to generate energy. However, in the absence of oxygen, they can switch to alcohol fermentation to produce energy. During alcohol fermentation, yeasts convert sugars such as glucose into ethyl alcohol (drinking alcohol) and carbon dioxide.
Alcohol fermentation is used in a variety of processes, including wine and beer production. For example, in wine making, yeasts ferment the sugars in grapes to produce alcohol and carbon dioxide. In beer production, yeasts ferment the sugars in malted barley to produce beer. This process is also used in baking, where the carbon dioxide produced by yeast fermentation causes dough to rise.