Cellular respiration is the aerobic harvesting of energy from food molecules, by chemically breaking down food-molecules in an energy releasing process. This process occurs in three main stages, and it banks energy in ATP molecules. First, glycolysis occurs in the cytoplasmic fluid of cells, producing pyruvate molecules that are transferred to the mitochondria. There, the citric acid cycle decomposes the pyruvate into carbon dioxide, and also produces electrons to fuel oxidative phosphorylation. This last stage involves the electron transport chain and chemiosmosis, where the bulk of ATP is made to carry out cellular processes. All in all, cellular respiration takes the chemical energy of stored food, and converts it to mechanical energy of internal processes, as well as external movement, such as this rhinoceros chewing food.