Answer:
Oxygen is needed to help the process of turning glucose into ATP. The initial step releases just two molecules of ATP for each glucose. The later steps release much more ATP.
Explanation:
In stage one, glucose is broken down in the cytoplasm of the cell in a process called glycolysis.
In stage two, the pyruvate molecules are transported into the mitochondria. The mitochondria are the organelles known as the energy "powerhouses" of the cells (Figure below). In the mitochondria, the pyruvate, which have been converted into a 2-carbon molecule, enter the Krebs cycle. Notice that mitochondria have an inner membrane with many folds, called cristae. These cristae greatly increase the membrane surface area where many of the cellular respiration reactions take place.
In stage three, the energy in the energy carriers enters an electron transport chain. During this step, this energy is used to produce ATP.
