The process of breaking down glucose for energy is called glycolysis. This metabolic pathway occurs in the cytoplasm of cells and is the first step in both aerobic and anaerobic respiration. During glycolysis, one molecule of glucose is converted into two molecules of pyruvate, producing a net gain of ATP and NADH in the process. This energy production is essential for cellular activities, especially in cells that rely on rapid energy release, such as muscle cells during intense exercise. Glycolysis is crucial for the overall metabolism of living organisms.