Cells need oxygen because oxygen is essential for a process called aerobic cellular respiration, which is how cells produce energy. In this process, oxygen acts as the final electron acceptor in the electron transport chain located in the mitochondria. This allows the cell to create a hydrogen ion gradient that drives the production of ATP (adenosine triphosphate), the molecule that stores and provides energy for nearly all cellular activities. Without oxygen, cells cannot efficiently generate ATP, leading to a lack of energy required for vital functions, which is why aerobic organisms depend on oxygen to survive.
