Question

Anaerobic respiration in yeast results in the formation of ethanol and CO${}_2$, whereas in muscle tissue lactate is the final product. In both the cases the yield of ATP is

• A. Four molecules
• B. Two molecules
• C. Two molecules in yeast and four molecules in muscle tissue
• D. Three molecules in yeast and two molecules in muscle tissue

Answer 1

The correct option is B Two molecules

When anaerobic respiration occurs, there is no oxygen to act as the final hydrogen acceptor and so the hydrogen cannot pass through the cytochrome system. As a result, both the Krebs cycle and the cytochrome system stages cannot take place. The only ATP produced is formed during glycolysis, that is, 2 ATP. Anaerobic respiration produces only 2 ATP compared to the 38 molecules of ATP produced during aerobic respiration. In both yeast and muscles, anaerobic respiration yields 2 ATP.

Therefore, the correct answer is option B.