The chemical process by which glucose is broken down to produce energy is called glycolysis. This metabolic pathway occurs in the cytoplasm of cells and converts glucose into two molecules of pyruvate, yielding a small amount of ATP and NADH in the process. Glycolysis is the first step in cellular respiration and can occur with or without oxygen. It is essential for energy production in both aerobic and anaerobic organisms, showcasing its fundamental role in metabolism.