In cell biology, a mitochondrion (plural mitochondria) is a
membrane-enclosed organelle found in most eukaryotic cells.These
organelles range from 0.5 to 10 micrometers (μm) in diameter.
Mitochondria are sometimes described as "cellular power plants"
because they generate most of the cell's supply of adenosine
triphosphate (ATP), used as a source of chemical energy. In addition
to supplying cellular energy, mitochondria are involved in a range of
other processes, such as signaling, cellular differentiation, cell
death, as well as the control of the cell cycle and cell growth.
Mitochondria have been implicated in several human diseases, including
mitochondrial disorders and cardiac dysfunction, and may play a role
in the aging process. The word mitochondrion comes from the Greek
μίτος or mitos, thread + χονδρίον or chondrion, granule.
Although most of a cell's DNA is contained in the cell nucleus, the
mitochondrion has its own independent genome. Further, its DNA shows
substantial similarity to bacterial genomes.
This is a extract on its role in producing energy
Energy conversion;
A dominant role for the mitochondria is the production of ATP, as reflected by the large number of proteins in the inner membrane for this task. This is done by oxidizing the major products of glucose, pyruvate, and NADH, which are produced in the cytosol.[7] This process of cellular respiration, also known as aerobic respiration, is dependent on the presence of oxygen. When oxygen is limited, the glycolytic products will be metabolized by anaerobic respiration, a process that is independent of the mitochondria.[7] The production of ATP from glucose has an approximately 13-fold higher yield during aerobic respiration compared to anaerobic respiration.[20] Recently it has been shown that plant mitochondria can produce a limited amount of ATP without oxygen by using the alternate substrate nitrite.[21]
and mitochondria diseases;
With their central place in cell metabolism, damage -- and subsequent
dysfunction -- in mitochondria is an important factor in a wide range
of human diseases. Mitochondrial disorders often present as
neurological disorders, but can manifest as myopathy, diabetes,
multiple endocrinopathy, or a variety of other systemic
manifestations.
Diseases caused by mutation in the mtDNA include Kearns-Sayre
syndrome, MELAS syndrome and Leber's hereditary optic neuropathy.In
the vast majority of cases, these diseases are transmitted by a female
to her children, as the zygote derives its mitochondria and hence its
mtDNA from the ovum. Diseases such as Kearns-Sayre syndrome, Pearson's
syndrome, and progressive external ophthalmoplegia are thought to be
due to large-scale mtDNA rearrangements, whereas other diseases such
as MELAS syndrome, Leber's hereditary optic neuropathy, myoclonic
epilepsy with ragged red fibers (MERRF), and others are due to point
mutations in mtDNA.
In other diseases, defects in nuclear genes lead to dysfunction of
mitochondrial proteins. This is the case in Friedreich's ataxia,
hereditary spastic paraplegia, and Wilson's disease.These diseases are
inherited in a dominance relationship, as applies to most other
genetic diseases.
A variety of disorders can be caused by nuclear mutations of oxidative
phosphorylation enzymes, such as coenzyme Q10 deficiency and Barth
syndrome. Environmental influences may interact with hereditary
predispositions and cause mitochondrial disease. For example, there
may be a link between pesticide exposure and the later onset of
Parkinson's disease.
Other pathologies with etiology involving mitochondrial dysfunction
include schizophrenia, bipolar disorder, dementia, Alzheimer's
disease, Parkinson's disease, epilepsy, stroke, cardiovascular
disease, retinitis pigmentosa, and diabetes mellitus. A common thread
thought to link these seemingly-unrelated conditions is cellular
damage causing oxidative stress. How exactly mitochondrial
dysfunctison fits into the etiology of these pathologies is yet to be
elucidated
You can ob find out more by going to Wikipeidia and typeing
Mitochondria into the search box
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