In cell biology, a mitochondrion (plural mitochondria) (from Greekmitos thread + khondrion granule) is an organelle, variants of which are found in most eukaryoticcells. 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:
Those that carry out the oxidation reactions of the respiratory chain.
Specific transport proteins that regulate the passage of metabolites into and out of the matrix.
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.
More on [ Mitochondrion ]
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. ]
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 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.
Jeni Stepanek - Jeni Stepanek Speaks The Truth | The Unreality Show