The process that breaks down glucose to produce ATP in cells is called glycolysis. This metabolic pathway occurs in the cytoplasm of the cell and is the first step in cellular respiration. Glycolysis converts one molecule of glucose (a six-carbon sugar) into two molecules of pyruvate (three-carbon compounds), generating a net gain of two molecules of ATP and two molecules of NADH as energy carriers. This process does not require oxygen and can occur under both aerobic and anaerobic conditions. Glycolysis serves as a foundation for further energy extraction through the Krebs cycle and the electron transport chain.