Question

a home brewer sets up a container with grain, water, and yeast. she opens the container twice per day to check the progress and gently stir the mixture. assuming she had all of the essential ingredients in the proper amounts, why cant she make beer?

Explanation:

Yeast can perform both cellular respiration (when oxygen is available) and fermentation (when oxygen is limited). Beer production relies on fermentation. Opening the container frequently supplies oxygen, allowing yeast to continue cellular respiration instead of switching to fermentation. Stirring further exposes the yeast to oxygen.

Answer:

Opening the container so frequently supplies the yeast with oxygen for cellular respiration; they never switch to fermentation. Stirring just makes it worse!