Final answer:
The presence of sugar affects the rate of cellular respiration in yeast. Yeast cells metabolize sugar through fermentation, which is less efficient than cellular respiration in the presence of oxygen. Fermentation produces ATP, but at a slower rate compared to aerobic respiration.
Step-by-step explanation:
The presence of sugar affects the rate of cellular respiration in yeast. Yeast cells metabolize sugars through the process of fermentation, which can occur in the absence of oxygen. During fermentation, yeast cells convert sugars into ethanol and carbon dioxide. This process provides some ATP, but it is not as efficient as cellular respiration in the presence of oxygen.
Therefore, when yeast cells are exposed to sugar, they undergo fermentation to produce ATP. However, the rate of ATP production is lower compared to cellular respiration under aerobic conditions, where glucose is completely oxidized to produce carbon dioxide, water, and a larger amount of ATP.