Mitochondria generate the energy that a cell needs to function properly. They are often described as the powerhouse of the cell. They are also involved in signaling, cellular differentiation, cell death, maintenance of cell growth and control of the cell cycle.
Mitochondria create chemical energy in the form of a chemical called adenosine triphosphate through a machinery known as the electron transport chain. The chain is created by four complexes created of groups of proteins and a fifth complex that is responsible for the final step of energy generation.
In order for the process to occur, electrons must be passed between the complexes of the chain. The first complex accepts the electrons. Electrons are then moved to the third complex while protons cross the inner mitochondrial wall. In the third complex the electrons are joined with others donated from the second complex. Complex three then passes the electrons to complex four as more protons move across the inner mitochondrial membrane.
In the fourth complex, electrons are joined to oxygen which creates water, and protons cross the membrane once again. A gradient is created as a result of the movement of so many protons. This gradient is used to rotate the fifth complex, creating an adenosine triphosphate with every rotation.