When skeletal muscle lacks sufficient oxygen there is an increased blood concentration of
options: a) pyruvic acid. b) glucose. c) ATP. d) None of the above.
The correct answer and explanation is:
The correct answer is a) pyruvic acid.
When skeletal muscle experiences insufficient oxygen, it results in anaerobic metabolism, primarily relying on glycolysis to produce energy. Glycolysis is a metabolic pathway that breaks down glucose to produce ATP, but when oxygen is scarce, the pyruvate produced in glycolysis cannot be processed through the aerobic pathway in the mitochondria (which requires oxygen). Instead, pyruvate is converted into lactic acid (lactate) in order to regenerate NAD+, which is essential for the continuation of glycolysis. This conversion occurs in the cytoplasm of the cell.
As a result, the accumulation of pyruvate is a consequence of the muscle’s reliance on anaerobic processes. Pyruvate is the immediate product of glycolysis, and without sufficient oxygen, it cannot enter the mitochondria to be fully oxidized into carbon dioxide and water. Instead, it is converted into lactate, which can accumulate in the muscle, contributing to fatigue and the sensation of “burning” during intense exercise.
It’s important to note that glucose levels and ATP concentrations might also fluctuate during intense activity, but the direct effect of insufficient oxygen leads to the accumulation of pyruvate, which is then converted into lactate. Increased pyruvate levels reflect the shift in metabolism from aerobic (oxygen-dependent) to anaerobic (oxygen-independent) pathways.
In the absence of sufficient oxygen, muscle cells adapt by increasing lactate production to help continue energy production, but this comes at the cost of reduced efficiency compared to aerobic respiration. This can lead to a decrease in muscle performance and the eventual onset of fatigue.