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In cell biology, a mitochondrion (plural mitochondria) (from Greek mitos thread + khondrion granule) is an organelle, variants of which are found in most eukaryotic cells. Mitochondria are sometimes described as "cellular power plants," because they convert organic materials into energy in the form of ATP via the process of oxidative phosphorylation. Usually a cell has hundreds or thousands of mitochondria, which can occupy up to 25% of the cell's cytoplasm. Mitochondria have their own DNA and according to the endosymbiotic theory may have descended from free-living prokaryotes that were closely related to rickettsia bacteria.

Mitochondrion structure


A mitochondrion contains outer and inner membranes composed of phospholipid bilayers and proteins. The two membranes, however, have very different properties. Inside the mitochondria is a compartment called the matrix that contains both proteins and DNA.

The outer membrane

The outer mitochondrial membrane, which encloses the entire organelle, has a protein-to-phospholipid ratio similar to the eucaryotic plasma membrane (about 1:1 by weight). It contains numerous integral proteins called porins, which contain a relatively large internal channel (about 2-3 nm) that is permeable to all molecules of 5000 daltons or less. Larger molecules can only traverse the outer membrane by active transport. It also contains a variety of enzymes involved in such diverse activities as the elongation of fatty acids, oxidation of epinephrine (adrenaline), and the degradation of tryptophan.

The inner membrane

The inner mitochondrial membrane contains proteins with four types of functions:
  1. Those that carry out the oxidation reactions of the respiratory chain.
  2. ATP synthase, which makes ATP in the matrix.
  3. Specific transport proteins that regulate the passage of metabolites into and out of the matrix.
  4. Protein import machinery.
It contains more than 100 different polypeptides, and has a very high protein-to-phospholipid ratio (more than 3:1 by weight, which is about 1 protein for 15 phospholipids). Additionally, the inner membrane is rich in an unusual phospholipid, cardiolipin, which is usually characteristic of bacterial plasma membranes. Unlike the outer membrane, the inner membrane does not contain porins, and is highly impermeable; almost all ions and molecules require special membrane transporters to enter or exit the matrix. In addition, there is a membrane potential across the inner membrane.

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Methionine restriction effects on mitochondrial biogenesis... [PubMed] http://bit.ly/91cjQs more parallels with calorie restriction
GeneOmX (Colby) Wed, 06 Jan 2010 05:26:13 -0000
Methionine restriction effects on mitochondrial biogenesis... [PubMed] http://bit.ly/91cjQs more parallels with calorie restriction
@TannersDad Only in cases of mitochondrial disease, which affects 1000 to 4000 of the around 4,115,590 babies born in the US yearly.
aspergerskitty (brandy wilson) Wed, 06 Jan 2010 04:35:34 -0000
@TannersDad Only in cases of mitochondrial disease, which affects 1000 to 4000 of the around 4,115,590 babies born in the US yearly.
Mito What? Child Mitochondrial Disease and it’s Impact, one family's story - http://cli.gs/QA14B
ChildrensRARE (Nicole Boice) Tue, 05 Jan 2010 16:21:19 -0000
Mito What? Child Mitochondrial Disease and it’s Impact, one family's story - http://cli.gs/QA14B
: Who Was Mitochondrial Eve? http://bit.ly/5luJhP
unfitblog (unfitblog) Tue, 05 Jan 2010 15:57:50 -0000
: Who Was Mitochondrial Eve? http://bit.ly/5luJhP
Just out in PNAS 'Mitochondrial gene in the nuclear genome induces reproductive barrier in rice' http://ow.ly/SQH6
PlantBiology (plant biology) Tue, 05 Jan 2010 08:05:43 -0000
Just out in PNAS 'Mitochondrial gene in the nuclear genome induces reproductive barrier in rice' http://ow.ly/SQH6
Gating of the mitochondrial permeability transition pore by thyroid hormone http://kele.es/snZ
Bio_Network (George Maine) Tue, 05 Jan 2010 05:01:29 -0000
Gating of the mitochondrial permeability transition pore by thyroid hormone http://kele.es/snZ

 
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Carnitine Palmitoyltransferase Deficiency - Newsletter for health care professionals and patients interested in CPT deficiency, a mitochondrial disorder of fat metabolism that causes muscle breakdown.
Meta Description: [ Newsletter for health care professionals and patients interested in CPT deficiency, a rare genetic disorder of fat metabolism that causes muscle breakdown. ]

Center for Inherited Disorders of Energy Metabolism (CIDEM) - A group of inter-disciplinary, clinical diagnostic laboratories which focus on disorders of mitochondrial function at Case Western Reserve University.

Foundation for a Cure for Mitochondrial Disease, Inc. - Fundraising for a cure for mitochondrial disease such as Melas, Merf, Narp, and Leighs Syndromes.

Mitochondrial Disease in Children - All seven of Kathleen's children have mitochondrial encephalomyopathy, and two of them have hearing loss as a reult.
Meta Description: [ mitochondrial myopathy (disease) information particularly about childrenwith neuromuscular disease ]

Mitochondrial Disorders Foundation of America - Support group for mitochondrial disorders.

Mitochondrial Myopathies - An information sheet compiled by NINDS, the National Institute of Neurological Disorders and Stroke.
Meta Description: [ Mitochondrial myopathies information sheet compiled by the National Institute of Neurological Disorders and Stroke (NINDS). ]

Nijmegen Center for Mitochondrial Disorders - Information about the facility as well as diagnostics and research.
Meta Description: [ Nijmegen Center for Mitochondrial Disorders ]

United Mitochondrial Disease Foundation - To promote research for the cure and treatment, and to provide support to families. The UMDF offers a library, patient registry, support information, conferences, research and grant updates, and a special section for physicians.

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