Split reins are a piece of equipment used for communicating with a horse while it is being ridden. Split reins are actually two separate, individual reins that are used together, with one rein on each side of the horse's neck.
As discussed above, mitochondria are the sites of respiration, and generate chemical energy in the form of ATP by metabolizing sugars, fats, and other chemical fuels with the assistance of molecular oxygen.
The mitochondria are organelles that are specialized to provide energy for cells by changing sugar (glucose) into usable energy. The chemical reactions that occur on the folds of the mitochondrion provide energy for the cell.