Here's why:
* Glycolysis is the first stage of cellular respiration. It occurs in the cytoplasm of the cell and breaks down glucose into pyruvate.
* Glycolysis does not require oxygen. It can function anaerobically, meaning it can occur without oxygen.
* In the presence of oxygen, pyruvate will enter the mitochondria for further breakdown in the Krebs cycle and electron transport chain (aerobic respiration). This process produces significantly more ATP (energy) than glycolysis alone.
* In the absence of oxygen, pyruvate is converted into lactate or ethanol through fermentation. This process produces a small amount of ATP and allows glycolysis to continue.
Therefore, glycolysis is the only stage of cellular respiration that can proceed normally in both aerobic and anaerobic conditions.
