Which process occurs in both aerobic and anaerobic respiration?

Glycolysis is the process that occurs in both aerobic and anaerobic respiration, making it a fundamental metabolic pathway for energy production in cells. This process occurs in the cytoplasm and breaks down glucose into two molecules of pyruvate, generating a net gain of two ATP molecules and two NADH molecules in the process.

In aerobic respiration, glycolysis is followed by the Krebs cycle and the electron transport chain, which require oxygen to further extract energy from the pyruvate. In contrast, anaerobic respiration does not use oxygen and may proceed through fermentation pathways after glycolysis, allowing organisms to continue producing energy in environments lacking oxygen. Thus, glycolysis serves as the initial step for both pathways, highlighting its essential role in cellular metabolism regardless of the presence of oxygen.