Yeast are a type of organism that can do both aerobic and anaerobic respiration, depending on whether or not oxygen is available. A scientist does an experiment on two identical populations of yeast. One population is grown in an open container and receives oxygen from the air, while the other is grown in a closed container. After two weeks of growth, he measures how many yeast are in each population. Which one will have the larger population, and why? Be sure to discuss ATP.

The results of the experiment should indicate that the yeasts grew well in both containers with almost no difference. This is because yeast is an organism referred as a facultative anaerobe. This means that they can also survive in oxygen-free environment. The yeast that was grown in open container utilized aerobic respiration while the one grown in a closed container switched to anaerobic respiration (fermentation). In both experiments, carbon dioxide was produced, but in the fermentation container lower amounts of ATP were produced. Fermentation also produced ethanol.

To explain the concept of ATP, fermentation produced a net of 2 ATP from gycolysis, ethanol and carbon dioxide. For the Aerobic respiration, it produced 36-38 ATP carbon dioxide and water.