The chemical process in cells that breaks down glucose for energy is called glycolysis. Glycolysis occurs in the cytoplasm of cells and involves a series of enzymatic reactions that convert glucose into pyruvate, producing a small amount of ATP (adenosine triphosphate) while also generating important metabolic intermediates. This process is the first step in cellular respiration, providing enough energy for cellular activities and serving as a critical pathway in both aerobic and anaerobic conditions.