Question

yeast cells are capable of anaerobic or aerobic respiration. you studied an experiment containing a mixture of yeast, glucose, and water to determine what type of respiration occurred. at the start of the experiment the yeast mixture bubbled and the balloon expanded. the mixture stopped bubbling.
the students concluded that the yeast respired aerobically at first and then switched to anaerobic respiration.
which two pieces of evidence support their conclusion?
students observations

	start of experiment	end of experiment
carbon dioxide	not assessed	present in balloon
water	present in flask	present in flask
alcohol	absent from flask	present in flask
oxygen	present in balloon	absent from balloon

a. the glucose was used up by the end of the experiment.
b. carbon dioxide was released and made the balloon expand.
c. water was still present in the flask at the end.
d. alcohol was produced during the experiment.
e. oxygen was present at the beginning but not at the end.

Explanation:

In aerobic respiration, glucose is consumed and carbon - dioxide is produced. In anaerobic respiration (after oxygen is used up), alcohol is produced. Glucose being used up (A) and alcohol production (D) indicate a shift from aerobic to anaerobic respiration by yeast.

Answer:

A. The glucose was used up by the end of the experiment.
D. Alcohol was produced during the experiment.