These pathways allow us to break down carbohydrate, fat and oxygen to live. Electrons from these food molecules are passed down a series of complex molecules called the electron transport chain. The final molecule in the chain, cytochrome oxidase, passes the electrons to oxygen One unique feature of mitochondria is that they have there own DNA molecules, mitochondrial DNA, which carries the genes containing the genetic message for several critical components of the electron transport chain. When enough mitochondria are not working correctly a disease may result. Mitochondrial diseases often involve the brain because of the tremendous energy requirements of the brain cells.
Mitochondrial diseases are very variable in their features so called clinical heterogeneity.
The variability results from the fact that different organ systems contain different amounts of diseased mitochondria and only those tissues with a high percentage of diseased mitochondria will be functional impaired. Mitochondrial diseases are whole body diseases but the exact features of the disease vary from one patient to another. Some patients will have predominately brain disease or nerve disease. Many mitochondrial diseases result in the accumulation of organic acids in the body. These are usually normal metabolic intermediates but when present in excess, the acidosis itself may be damaging or even life-threatening.