Cellular respiration is the metabolic process through which biochemical energy is harnessed from nutrient molecules to sustain life. This complex series of reactions converts the chemical potential energy stored in organic compounds, such as glucose, into adenosine triphosphate (ATP), which serves as the primary energy currency for nearly all cellular activities. The overall process involves multiple interconnected stages, including glycolysis, the citric acid cycle, and oxidative phosphorylation. These stages systematically dismantle complex molecules, extracting high-energy electrons that are used to establish electrochemical gradients across specialized membranes. The flow of protons through enzyme complexes ultimately drives the synthesis of ATP, providing the usable energy required for active transport, chemical synthesis, and mechanical work within the cell.