What is a byproduct of the anaerobic pathway?

The anaerobic pathway, which occurs in the absence of oxygen, primarily involves the breakdown of glucose for energy. During this process, pyruvate is produced from glycolysis, and in the absence of oxygen, it is converted into lactic acid. This conversion allows for the regeneration of NAD+, which is essential for glycolysis to continue producing ATP in anaerobic conditions. Lactic acid accumulation can lead to muscle fatigue but is a critical component of energy production during short bursts of high-intensity exercise.

In contrast, the other choices represent different substances not primarily associated with the anaerobic pathway. Carbon dioxide is a byproduct of aerobic respiration, creatine is found in muscle tissues and is involved in ATP replenishment but is not a direct byproduct of anaerobic metabolism, and water is largely produced during aerobic processes as well. Understanding lactic acid's role in energy production helps highlight the efficiency and limitations of anaerobic metabolism.