The process that describes the breaking down of glucose in cells to produce energy is called glycolysis. This metabolic pathway occurs in the cytoplasm of cells and involves a series of enzymatic reactions that convert one molecule of glucose into two molecules of pyruvate, producing a small amount of ATP and NADH as energy carriers in the process. Glycolysis is the first step of both aerobic and anaerobic respiration, marking the initial phase of glucose metabolism in living organisms.