Yeasts are single-celled eukaryotes that don't have a mitochondrion. can they exist in an environment without oxygen?
a. yes, yeasts can exist in an oxygen-poor environment. they will only be able to produce 2 net atp va fermentation, but the absence of oxygen will not kill the organisms.
b. no, the presence of oxygen will kill yeast because they will not be able to undergo fermentation.

Letter a. Yes, yeasts can exist in an oxygen-poor environment.

Explanation:

Mitochondria are an organelle that we can find in the majority of eukaryotic cells. Mitochondria help in produces the energetical molecule of ATP. We start with one molecule of glucose that passes through a process called glycolysis to convert glucose into pyruvate. This pyruvate molecule can follow two pathways: when oxygen is available the pyruvate enter into the Krebs cycle and proceeds to the respiratory chain in the mitochondria, when oxygen is not present, pyruvate pass into another pathway, one is the alcoholic fermentation producing ethanol and dioxide of carbon.

As yeast are a eukaryotic organism, they have mitochondria and can grow in the presence of oxygen. When oxygen is absent yeast can grow using the fermentation pathway producing alcohol.