Biological Systems MCAT Practice Exam

What occurs during the process of anaerobic glycolysis in muscle tissues?

1. Increased oxygen utilization

2. Production of lactic acid

3. Formation of carbon dioxide

4. Enhanced aerobic metabolism

The correct answer is: Production of lactic acid

During anaerobic glycolysis in muscle tissues, glucose is metabolized to generate energy when oxygen availability is low. This process occurs primarily during intense physical activity when the oxygen supply is insufficient to support aerobic respiration. The key outcome of anaerobic glycolysis is the production of lactic acid. When pyruvate is produced through the breakdown of glucose, it cannot enter the aerobic pathways due to the lack of oxygen. Instead, pyruvate is converted into lactic acid, allowing for the regeneration of NAD+, which is crucial for the continuation of glycolysis. This enables the muscle cells to produce ATP quickly, providing immediate energy despite the inefficiencies and byproducts associated with the anaerobic process. The transformation of pyruvate into lactic acid also plays a role in buffering pH levels within the muscle, although in too large amounts, it can contribute to muscle fatigue. This highlights the focus of anaerobic glycolysis on rapid energy production, particularly during peak exertion when the demand for ATP exceeds the oxygen supply available for aerobic processes.