Mitochondrion

A mitochondrion (pl. mitochondria) is an <a href="/facts/Organelle/vhDFnGbs">organelle</a> found in the <a href="/facts/Cell_(biology)/bLM9UQvy">cells</a> of most <a href="/facts/Eukaryote/SkwyPLMA">eukaryotes</a>, such as <a href="/facts/Animal/4b8J33nd">animals</a>, <a href="/facts/Plant/X5BMDMvS">plants</a> and <a href="/facts/Fungi/BHo5DP59">fungi</a>. Mitochondria have a double <a href="/facts/Lipid_bilayer/CQKQ9l3g">membrane</a> structure and use <a href="/facts/Aerobic_respiration/kb6gpsvL">aerobic respiration</a> to generate <a href="/facts/Adenosine_triphosphate/nB9bwgcU">adenosine triphosphate</a> (ATP), which is used throughout the cell as a source of <a href="/facts/Chemical_energy/Y3VP3Ifq">chemical energy</a>. They were discovered by <a href="/facts/Albert_von_K%25C3%25B6lliker/eYudoEHx">Albert von Kölliker</a> in 1857 in the voluntary muscles of insects. The term mitochondrion, meaning a thread-like granule, was coined by <a href="/facts/Carl_Benda/9oxjSjjv">Carl Benda</a> in 1898. The mitochondrion is popularly nicknamed the "powerhouse of the cell", a phrase popularized by <a href="/facts/Philip_Siekevitz/83mH19S4">Philip Siekevitz</a> in a 1957 <a href="/facts/Scientific_American/jkl8bhUN">Scientific American</a> article of the same name.
Some cells in some <a href="/facts/Multicellular_organism/rk8QBF7o">multicellular organisms</a> lack mitochondria (for example, mature mammalian <a href="/facts/Red_blood_cell/Kggpq8Jh">red blood cells</a>). The multicellular <a href="/facts/Animal/4b8J33nd">animal</a> <a href="/facts/Henneguya_zschokkei/qERxQ1Y3">Henneguya salminicola</a> is known to have retained mitochondrion-related organelles despite a complete loss of their mitochondrial genome. A large number of <a href="/facts/Unicellular_organism/9PQsRuHU">unicellular organisms</a>, such as <a href="/facts/Microsporidia/z01Q4Xfl">microsporidia</a>, <a href="/facts/Parabasalid/C77yR5fg">parabasalids</a> and <a href="/facts/Diplomonad/7Wxd7geB">diplomonads</a>, have reduced or transformed their mitochondria into other structures, e.g. <a href="/facts/Hydrogenosome/EYmA39qx">hydrogenosomes</a> and <a href="/facts/Mitosome/J1JYIjYv">mitosomes</a>. The <a href="/facts/Oxymonad/KzfJVvt1">oxymonads</a> <a href="/facts/Monocercomonoides/IB0rtV44">Monocercomonoides</a>, <a href="/facts/Streblomastix/rJp62t5q">Streblomastix</a>, and Blattamonas completely lost their mitochondria.
Mitochondria are commonly between 0.75 and 3 <a href="/facts/Micrometre/7eDFxD2L">μm</a>2 in cross section, but vary considerably in size and structure. Unless specifically <a href="/facts/Staining/jqGqWEE1">stained</a>, they are not visible. The mitochondrion is composed of compartments that carry out specialized functions. These compartments or regions include the outer membrane, <a href="/facts/Intermembrane_space/lEt0NyqY">intermembrane space</a>, <a href="/facts/Inner_mitochondrial_membrane/IJIE4o0h">inner membrane</a>, <a href="/facts/Crista/2PUrXT28">cristae</a>, and <a href="/facts/Mitochondrial_matrix/tgC0ENLv">matrix</a>.
In addition to supplying cellular energy, mitochondria are involved in other tasks, such as <a href="/facts/Cell_signaling/6oYAVP9I">signaling</a>, <a href="/facts/Cellular_differentiation/bCVqUG7w">cellular differentiation</a>, and <a href="/facts/Apoptosis/8dVzSm4y">cell death</a>, as well as maintaining control of the <a href="/facts/Cell_cycle/nLMT7K4r">cell cycle</a> and <a href="/facts/Cell_growth/wbArMaJU">cell growth</a>. <a href="/facts/Mitochondrial_biogenesis/JBstUdkX">Mitochondrial biogenesis</a> is in turn temporally coordinated with these cellular processes. 
Mitochondria are implicated in human disorders and conditions such as <a href="/facts/Mitochondrial_disease/r79sg24J">mitochondrial diseases</a>, <a href="/facts/Heart_failure/7fckX3Jm">cardiac dysfunction</a>, heart failure, and <a href="/facts/Autism/6MTwMNoJ">autism</a>.
The number of mitochondria in a cell vary widely by <a href="/facts/Organism/j8JkL09u">organism</a>, <a href="/facts/Tissue_(biology)/H7CpML7A">tissue</a>, and cell type. A mature red blood cell has no mitochondria, whereas a <a href="/facts/Hepatocyte/USpvDz1n">liver cell</a> can have more than 2000. 
Although most of a eukaryotic cell's <a href="/facts/DNA/nB89Iauz">DNA</a> is contained in the <a href="/facts/Cell_nucleus/D7sFRa3c">cell nucleus</a>, the mitochondrion has <a href="/facts/Mitochondrial_DNA/goC0ex0X">its own genome</a> ("mitogenome") that is similar to <a href="/facts/Bacteria/wC8xSCsU">bacterial</a> genomes. This finding has led to general acceptance of the <a href="/facts/Symbiogenesis/2gHlgj4j">endosymbiotic hypothesis</a> - that free-living prokaryotic ancestors of modern mitochondria permanently fused with eukaryotic cells in the distant past, evolving such that modern animals, plants, fungi, and other eukaryotes <a href="/facts/Cellular_respiration/kb6gpsvL">respire</a> to generate <a href="/facts/Adenosine_triphosphate/nB9bwgcU">cellular energy</a>.

Mitochondrion open-in-new

Mitochondrion