Yeast can respire in both ways. Yeast gets more energy from aerobic respiration, but when it runs out of oxygen it does not die. It can continue to respire anaerobically, but it does not get so much energy from the sugar. Yeast produces ethanol when it respires anaerobically but if any was produced in bread-making, it would evaporate away fully in the baking process.
The two word equations for years are:
Glucose + Oxygen = Carbon Dioxide + Water + Energy
Glucose = Carbon Dioxide + Ethanol + Energy
Anaerobic respiration in yeast is used during brewing and bread-making. Aerobic respiration or anaerobic respiration can occur in yeast.In bread-making, the yeast will start off respiring aerobically, water is produced and also carbon dioxide to make the dough rise. When the air runs out, the yeast begins to respire anaerobically.
