Here's why:
* Glycolysis is the first stage of cellular respiration. It occurs in the cytoplasm and breaks down glucose into pyruvate. This process does not require oxygen and can therefore occur in the absence of oxygen.
* The other stages of cellular respiration (Krebs cycle and electron transport chain) require oxygen and are considered aerobic.
While glycolysis can occur anaerobically, it is not the most efficient energy production method. It produces only a small amount of ATP compared to the full aerobic respiration process.
Important Note: Some textbooks may refer to fermentation as the anaerobic process of cellular respiration, but fermentation is actually a separate metabolic pathway that follows glycolysis under anaerobic conditions. It allows for the regeneration of NAD+ for glycolysis to continue, but it does not directly generate ATP.
