Answer:
Respiration might occur in the presence and absence of oxygen known as the aerobic respiration and anaerobic respiration. The ATP molecules are produced more in number in aerobic respiration.
The yeast has the ability to undergo the process of anaerobic respiration and its end product are alcohol, carbon dioxide and 2 moles of ATP. The yeast is grown on maltose medium but unable to produce alcohol because of the presence of oxygen in the medium. The oxygen might acts as poison or inhibit the process of anaerobic respiration.