Yeast is a facultative anaerobe. This means that alcohol fermentation takes place only if:

1 the temperature is close to 37°C

2 the atmosphere does not contain oxygen

3 sugar is provided to the cells

4 light is provided to the cells

2 the atmosphere does not contain oxygen

Explanation:

The yeast is a faculties anaerobe in that in the absence of oxygen, it is able to alter its metabolism for growth using alcoholic fermentation and also experience better growth in the presence of oxygen. They can grow both in the presence and absence of oxygen