During cellular respiration, organisms use oxygen to turn glucose into carbon dioxide, water, and energy in the form of ATP. The process has three stages: glycolysis , the Krebs cycle, and the electron transport chain. Glycolysis in the cytoplasm ), breaks down 1 glucose into 2 pyruvate and 2 ATP. The Krebs cycle (in the mitochondrion's matrix), provides the hydrogen and electrons needed for the electron transport chain. Another 2 are formed here. The electron transport chain (on the inner mitochondrial membrane) forms 32 ATP through oxidative phosphorylation .