Optometry Admission Test (OAT) Practice

What is pyruvate converted to during anaerobic respiration in muscles or yeast?

1. Glucose

2. Lactic acid or ethanol

3. Acetyl CoA

4. Carbon dioxide

The correct answer is: Lactic acid or ethanol

During anaerobic respiration, the conversion of pyruvate occurs in two distinct pathways, depending on the organism involved. In muscle tissue, pyruvate is converted to lactic acid through a process known as lactic acid fermentation. This occurs when oxygen levels are low, and the cell must regenerate NAD+ to allow glycolysis (the initial step of glucose metabolism) to continue. The accumulation of lactic acid can lead to temporary fatigue in muscles during vigorous exercise. In yeast, pyruvate is converted to ethanol and carbon dioxide through alcoholic fermentation. This process is utilized by yeast cells when oxygen is scarce, allowing them to produce energy while also regenerating NAD+. The ethanol produced is significant in brewing and fermentation industries. Both of these conversions highlight the importance of anaerobic respiration in energy production under oxygen-limited conditions, demonstrating how organisms adapt to survive and maintain metabolic functions despite a lack of oxygen. The correct answer effectively encapsulates these processes by referring to lactic acid in muscles and ethanol in yeast as the primary products of pyruvate conversion during anaerobic respiration.