Yeast Metabolism

Yeasts metabolize sugars for energy, and produce carbon dioxide gas and alcohol as by-products of that metabolism. The overall equation for the conversion that takes place in yeast cells is this:

In making beer and wine, the carbon dioxide escapes from the fermenting liquid, and alcohol accumulates. In making bread, both carbon dioxide and alcohol are trapped by the dough, and both are expelled from the dough by the heat of baking.