NationMaster - Encyclopedia: Mitochondrion

In cell biology, a mitochondrion (plural mitochondria) is a membrane-enclosed organelle that is found in most eukaryotic cells.^[1] Mitochondria are sometimes described as "cellular power plants," because they generate most of the cell's supply of ATP, used as a source of chemical energy. The number of mitochondria in a cell varies widely by organism and tissue type. Many cells possess only a single mitochondrion, while others can contain several thousand mitochondria.^[2]^[3] Image File history File linksMetadata Mitochondrion_186. ... A micrograph is a photograph or similar image taken through a microscope or similar device to show a magnified image of an item. ... This article or section includes a list of works cited or a list of external links, but its sources remain unclear because it lacks in-text citations. ... Schematic of typical animal cell, showing subcellular components. ... Kingdoms Animalia - Animals Fungi Plantae - Plants Chromalveolata Protista Alternative phylogeny Unikonta Opisthokonta Metazoa Choanozoa Eumycota Amoebozoa Bikonta Apusozoa Cabozoa Rhizaria Excavata Corticata Archaeplastida Chromalveolata Animals, plants, fungi, and protists are eukaryotes (IPA: ), organisms whose cells are organized into complex structures by internal membranes and a cytoskeleton. ... Drawing of the structure of cork as it appeared under the microscope to Robert Hooke from Micrographia which is the origin of the word cell being used to describe the smallest unit of a living organism Cells in culture, stained for keratin (red) and DNA (green) The cell is the... Adenosine 5-triphosphate (ATP) is a multifunctional nucleotide that is most important as a molecular currency of intracellular energy transfer. ...

Although most of a cell's DNA is contained in the cell nucleus, mitochondria have their own independent genomes. This DNA shows similarity to bacterial genomes and according to the endosymbiotic theory, mitochondria are descended from free-living prokaryotes. The word mitochondrion comes from the Greek μίτος or mitos, thread + χονδρίον or khondrion, granule. HeLa cells stained for DNA with the Blue Hoechst dye. ... Mitochondrial DNA (some captions in German) Mitochondrial DNA (mtDNA) is the DNA located in organelles called mitochondria. ... Phyla Actinobacteria Aquificae Chlamydiae Bacteroidetes/Chlorobi Chloroflexi Chrysiogenetes Cyanobacteria Deferribacteres Deinococcus-Thermus Dictyoglomi Fibrobacteres/Acidobacteria Firmicutes Fusobacteria Gemmatimonadetes Lentisphaerae Nitrospirae Planctomycetes Proteobacteria Spirochaetes Thermodesulfobacteria Thermomicrobia Thermotogae Verrucomicrobia Bacteria (singular: bacterium) are unicellular microorganisms. ... It has been suggested that Proto-mitochondrion be merged into this article or section. ... Prokaryotes (pro-KAR-ee-oht) (from Old Greek pro- before + karyon nut or kernel, referring to the cell nucleus, + suffix -otos, pl. ...

Mitochondrion structure

A mitochondrion contains inner and outer membranes composed of phospholipid bilayers and proteins. The two membranes, however, have different properties. Because of this double-membraned organization, there are 5 distinct compartments within mitochondria. There is the outer membrane, the intermembrane space (the space between the outer and inner membranes), the inner membrane, the cristae space (formed by infoldings of the inner membrane), and the matrix (space within the inner membrane). Mitochondria range from 1 to 10 micrometers (μm) in size. Image File history File links Diagram_of_a_human_mitochondrion. ... A DPPC bilayer simulation Color scheme: PO4 = green, N(CH3)3 = violet, water = blue, terminal CH3 = yellow, O = red, glycol C = brown, chain C = grey In biology and chemistry, a lipid bilayer is a membrane or zone of membrane composed only of lipid. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ...

Outer membrane

The outer mitochondrial membrane, which encloses the entire organelle, has a protein-to-phospholipid ratio similar to the eukaryotic plasma membrane (about 1:1 by weight). It contains numerous integral proteins called porins. Integral membrane protein of the transmembrane type An Integral Membrane Protein (IMP) is a protein molecule (or assembly of proteins) that in most cases spans the biological membrane with which it is associated (especially the plasma membrane) or which, in any case, is sufficiently embedded in the membrane to remain... The introduction to this article provides insufficient context for those unfamiliar with the subject matter. ...

Intermembrane space

The intermembrane space is the space between the outer membrane and the inner membrane. The intermembrane space is the region between the inner membrane and the outer membrane of a mitochondrion or a chloroplast. ...

Inner membrane

The inner mitochondrial membrane contains proteins with four types of functions: ^[2] Mitochondria structure: (1) inner membrane, (2) outer membrane, (3)cristae, (4) matrix The mitochondrial inner membrane forms internal compartments known as cristae, which allow greater space for the proteins such as cytochromes to function properly and efficiently. ...

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. This phospholipid was originally discovered in beef hearts in 1942 and is usually characteristic of mitochondrial and bacterial plasma membranes.^[4] 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. An ATP synthase (EC 3. ... Adenosine 5-triphosphate (ATP) is a multifunctional nucleotide that is most important as a molecular currency of intracellular energy transfer. ... A metabolite is the product of metabolism. ... Peptides are the family of molecules formed from the linking, in a defined order, of various amino acids. ... Cardiolipin Cardiolipin (alternate image) Cardiolipin (bisphosphatidyl glycerol) is an important component of the inner mitochondrial membrane, where it constitutes about 20% of the total lipid. ...

The inner mitochondrial membrane is compartmentalized into numerous cristae, which expand the surface area of the inner mitochondrial membrane, enhancing its ability to generate ATP. In typical liver mitochondria, for example, the surface area, including cristae, is about five times that of the outer membrane. Mitochondria of cells which have greater demand for ATP, such as muscle cells, contain more cristae than typical liver mitochondria. Mitochondria structure : 1) Inner membrane 2) Outer membrane 3) Crista 4) Matrix Cristae (singular crista) are the internal compartments formed by the inner membrane of a mitochondrion. ... The liver is an organ present in vertebrates and some other animals. ...

Mitochondrial matrix

The matrix is the space enclosed by the inner membrane. The matrix is important in the production of ATP with the aid of the ATP synthase contained in the inner membrane. The matrix contains a highly concentrated mixture of hundreds of enzymes, in addition to the special mitochondrial ribosomes, tRNA, and several copies of the mitochondrial DNA genome. Of the enzymes, the major functions include oxidation of pyruvate and fatty acids, and the citric acid cycle.^[2] In biology, the word matrix is used for the material between animal or plant cells, or generally the material (or tissue) in which more specialized structures are embedded, and also specifically for one part of the mitochondrion. ... Image File history File links MitochondrionCAM.jpgâ€Ž [edit] Summary This is an image of a frozen-hydrated rat liver mitochondrion based on work done at the Wadsworth Centers Resource for Visualization of Biological Complexity (http://www. ... Image File history File links MitochondrionCAM.jpgâ€Ž [edit] Summary This is an image of a frozen-hydrated rat liver mitochondrion based on work done at the Wadsworth Centers Resource for Visualization of Biological Complexity (http://www. ... Figure 1: Ribosome structure indicating small subunit (A) and large subunit (B). ... Transfer RNA (abbreviated tRNA) is a small RNA chain (74-93 nucleotides) that transfers a specific amino acid to a growing polypeptide chain at the ribosomal site of protein synthesis during translation. ... Mitochondrial DNA (some captions in German) Mitochondrial DNA (mtDNA) is the DNA located in organelles called mitochondria. ... In biology the genome of an organism is the whole hereditary information of an organism that is encoded in the DNA (or, for some viruses, RNA). ... Pyruvate (CH3COCOOâˆ’) is the ionized form of pyruvic acid. ... In chemistry, especially biochemistry, a fatty acid is a carboxylic acid (or organic acid), often with a long aliphatic tail (long chains), either saturated or unsaturated. ... Overview of the citric acid cycle The citric acid cycle (also known as the tricarboxylic acid cycle, the TCA cycle, or the Krebs cycle, after Hans Adolf Krebs who identified the cycle) is a series of chemical reactions of central importance in all living cells that use oxygen as part...

Mitochondria possess their own genetic material, and the machinery to manufacture their own RNAs and proteins. (See: protein synthesis). A published human mitochondrial DNA sequence revealed 16,569 base pairs encoding 37 total genes, 24 tRNA and rRNA genes and 13 peptide genes.^[5] The 13 mitochondrial peptides in humans are integrated into the inner mitochondrial membrane, along with proteins encoded by genes that reside in the host cell's nucleus. Ribonucleic acid or RNA is a nucleic acid polymer consisting of nucleotide monomers that plays several important roles in the processes that translate genetic information from deoxyribonucleic acid (DNA) into protein products; RNA acts as a messenger between DNA and the protein synthesis complexes known as ribosomes, forms vital portions... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... Protein synthesis is the creation of proteins using DNA and RNA. Biological and artificial methods for creation of proteins differ significantly. ... Transfer RNA (abbreviated tRNA) is a small RNA chain (74-93 nucleotides) that transfers a specific amino acid to a growing polypeptide chain at the ribosomal site of protein synthesis during translation. ... A non-coding RNA (ncRNA) is any RNA molecule that functions without being translated into a protein. ... Peptides (from the Greek Ï€ÎµÏ€Ï„Î¿Ï‚, digestible), are the family of short molecules formed from the linking, in a defined order, of various Î±-amino acids. ... Peptides are the family of molecules formed from the linking, in a defined order, of various amino acids. ... A representation of the 3D structure of myoglobin, showing coloured alpha helices. ... For other uses, see Gene (disambiguation). ... HeLa cells stained for DNA with the Blue Hoechst dye. ...

Mitochondrial functions

Although it is well known that the mitochondria convert organic materials into cellular energy in the form of ATP, mitochondria play an important role in many metabolic tasks, such as: Adenosine 5-triphosphate (ATP) is a multifunctional nucleotide that is most important as a molecular currency of intracellular energy transfer. ... A few of the metabolic pathways in a cell. ...

Some mitochondrial functions are performed only in specific types of cells. For example, mitochondria in liver cells contain enzymes that allow them to detoxify ammonia, a waste product of protein metabolism. A mutation in the genes regulating any of these functions can result in mitochondrial diseases. A section of mouse liver showing an apoptotic cell indicated by an arrow Apoptosis (pronounced apo tÅ sis) is a process of suicide by a cell in a multicellular organism. ... Glutamate is the anion of glutamic acid. ... Drawing by Santiago RamÃ³n y Cajal of neurons in the pigeon cerebellum. ... Illustration of a redox reaction Redox (shorthand for oxidation/reduction reaction) describes all chemical reactions in which atoms have their oxidation number (oxidation state) changed. ... Structure of Heme b A heme or haem is a prosthetic group that consists of an iron atom contained in the center of a large heterocyclic organic ring called a porphyrin. ... This article is about the chemical family of steroids. ... For other uses, see Ammonia (disambiguation). ... Mitochondrial diseases are a group of disorders relating to the mitochondria, the organelles that are the powerhouses of the eukaryotic cells that comprise higher-order lifeforms (including humans). ...

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 glycolysis: pyruvate and NADH that are produced in the cytosol. 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 metabolised by anaerobic respiration, a process that is independent of the mitochondria. The production of ATP from glucose has an approximately 13-fold higher yield during aerobic respiration compared to anaerobic respiration.^[6] Adenosine 5-triphosphate (ATP) is a multifunctional nucleotide that is most important as a molecular currency of intracellular energy transfer. ... Glycolysis is a metabolic pathway by which a 6-carbon glucose (Glc) molecule is oxidized to two molecules of pyruvic acid (Pyr). ... Pyruvate (CH3COCOOâˆ’) is the ionized form of pyruvic acid. ... Nicotinamide adenine dinucleotide (NAD+) Nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP) are two important coenzymes found in cells. ... Cellular respiration describes the metabolism reactions and processes that take place in a cell to obtain biochemical energy from fuel molecules. ... This article or section should be merged with aerobic metabolism. ... General Name, symbol, number oxygen, O, 8 Chemical series nonmetals, chalcogens Group, period, block 16, 2, p Appearance colorless (gas) very pale blue (liquid) Standard atomic weight 15. ... Anaerobic respiration refers to the oxidation of molecules in the absence of oxygen to produce energy, in opposition to Aerobic respiration which does use oxygen. ...

Pyruvate: the citric acid cycle

Each pyruvate molecule produced by glycolysis is actively transported across the inner mitochondrial membrane, and into the matrix where it is oxidized and combined with coenzyme A to form CO₂, acetyl-CoA and NADH. It has been suggested that this article or section be merged with pyruvate dehydrogenase complex. ... Overview of the citric acid cycle The citric acid cycle (also known as the tricarboxylic acid cycle, the TCA cycle, or the Krebs cycle, after Hans Adolf Krebs who identified the cycle) is a series of chemical reactions of central importance in all living cells that use oxygen as part... Sodium-Potassium pump, an example of Primary active transport secondary active transport Active transport (sometimes called active uptake) is the mediated transport of biochemicals, and other atomic/molecular substances, across membranes. ... Coenzyme A (CoA, CoASH, or HSCoA) is a coenzyme, notable for its role in the synthesis and oxidization of fatty acids, and the oxidation of pyruvate in the citric acid cycle. ... Categories: Biochemistry stubs | Thiols ... Nicotinamide adenine dinucleotide (NAD+) Nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP) are two important coenzymes found in cells. ...

The acetyl-CoA is the primary substrate to enter the citric acid cycle , also known as the tricarboxylic acid (TCA) cycle or Krebs cycle. The enzymes of the citric acid cycle are located in the mitochondrial matrix with the exception of succinate dehydrogenase, which is bound to the inner mitochondrial membrane. The citric acid cycle oxidizes the acetyl-CoA to carbon dioxide and in the process produces reduced cofactors (three molecules of NADH and one molecule of FADH₂), that are a source of electrons for the electron transport chain, and a molecule of GTP (that is readily converted to an ATP). Overview of the citric acid cycle The citric acid cycle (also known as the tricarboxylic acid cycle, the TCA cycle, or the Krebs cycle, after Hans Adolf Krebs who identified the cycle) is a series of chemical reactions of central importance in all living cells that use oxygen as part... Succinate - coenzyme Q reductase also called succinate dehydrogenase is an enzyme complex found in the matrix part of the inner mitochondrial membrane. ... Nicotinamide adenine dinucleotide (NAD+) Nicotinamide adenine dinucleotide (NAD) and nicotinamide adenine dinucleotide phosphate (NADP) are two important coenzymes found in cells. ... Flavin is also the name of a commune in the Aveyron département, in France Flavin adenine dinucleotide (FAD), upper, reduced FAD (FADH2), lower Flavin is a tricyclic heteronuclear organic ring whose biochemical source is the vitamin riboflavin. ... The Electron Transport Chain. ... Guanosine triphosphate (GTP) is also known as guanosine-5-triphosphate. ...

NADH and FADH₂: the electron transport chain

The redox energy from NADH and FADH₂ is transferred to oxygen (O₂) in several steps via the electron transport chain. These energy-rich molecules are produced within the matrix via the citric acid cycle but are also produced in the cytoplasm by glycolysis; reducing equivalents from the cytoplasm can be imported via the malate-aspartate shuttle system of antiporter proteins or feed into the electron transport chain using a glycerol phosphate shuttle. Protein complexes in the inner membrane (NADH dehydrogenase, cytochrome c reductase and cytochrome c oxidase) perform the transfer and the incremental release of energy is used to pump protons (H⁺) into the intermembrane space. This process is efficient but a small percentage of electrons may prematurely reduce oxygen, forming reactive oxygen species such as superoxide. This can cause oxidative stress in the mitochondria and may contribute to the decline in mitochondrial function associated with the aging process.^[7] The Electron Transport Chain. ... The Electron Transport Chain. ... Image File history File links Biological_cell. ... Image File history File links Biological_cell. ... Schematic of typical animal cell, showing subcellular components. ... The nucleolus is contained within the cell nucleus. ... HeLa cells stained for DNA with the Blue Hoechst dye. ... Figure 1: Ribosome structure indicating small subunit (A) and large subunit (B). ... This article or section is in need of attention from an expert on the subject. ... The endoplasmic reticulum or ER is an organelle found in all eukaryotic cells that is an interconnected network of tubules, vesicles and cisternae that is responsible for several specialized functions: Protein translation, folding, and transport of proteins to be used in the cell membrane (e. ... Micrograph of Golgi apparatus, visible as a stack of semicircular black rings near the bottom. ... The eukaryotic cytoskeleton. ... The endoplasmic reticulum or ER (endoplasmic means within the cytoplasm, reticulum means little net) is an organelle found in all eukaryotic cells. ... Schematic of typical animal cell, showing subcellular components. ... It has been suggested that Cytoplast be merged into this article or section. ... Organelles labeled at upper left. ... A centriole in biology is a barrel shaped microtubule structure found in most animal cells and algae though not frequently in plants. ... Glycolysis is a metabolic pathway by which a 6-carbon glucose (Glc) molecule is oxidized to two molecules of pyruvic acid (Pyr). ... The malate-aspartate shuttle (sometimes also the malate shuttle) is a system of two antiporter proteins located in the inner membrane of the mitochondrion in eukaryotes. ... An antiporter is an integral membrane protein that is involved in secondary active transport. ... The glycerol-3-phosphate shuttle is a mechanism that regenerates NAD+ from NADH, a by-product of glycolysis. ... The Electron Transport Chain. ... NADH dehydrogenase NADH dehydrogenase (EC 1. ... CoQ Cytochrome c reductase The Coenzyme Q - cytochrome c reductase complex, sometimes called the cytochrome bc1 complex, and at other times Complex III, is the third complex in the electron transfer chain (PDB 1KYO, EC 1. ... Cytochrome c oxidase The enzyme cytochrome c oxidase (PDB 2OCC, EC 1. ... Hydronium is the common name for the cation H3O+. Nomenclature According to IUPAC ion nomenclature, it should be referred to as oxonium. ... Reactive oxygen species (ROS) include oxygen ions, free radicals and peroxides both inorganic and organic. ... Lewis electron configuration of superoxide. ... Oxidative stress is a medical term for damage to animal or plant cells (and thereby the organs and tissues composed of those cells) caused by reactive oxygen species, which include (but are not limited to) superoxide, singlet oxygen, peroxynitrite or hydrogen peroxide. ...

As the proton concentration increases in the intermembrane space, a strong electrochemical gradient is established across the inner membrane. The protons can return to the matrix through the ATP synthase complex and their potential energy is used to synthesize ATP from ADP and inorganic phosphate (P_i). This process is called chemiosmosis and was first described by Peter Mitchell^[8]^[9] who was awarded the 1978 Nobel Prize in Chemistry for his work. Later, part of the 1997 Nobel Prize in Chemistry was awarded to Paul D. Boyer and John E. Walker for their clarification of the working mechanism of ATP synthase. In cellular biology, an electrochemical gradient refers to the electrical and chemical properties across a membrane. ... An ATP synthase (EC 3. ... Adenosine 5-triphosphate (ATP) is a multifunctional nucleotide that is most important as a molecular currency of intracellular energy transfer. ... Chemiosmosis is the diffusion of ions across a membrane. ... Peter D. Mitchell (September 29, 1920- April 10, 1992) was a British biochemist who was awarded the 1978 Nobel Prize for Chemistry for formulation of the chemiosmotic theory of mitochondrial function. ... The Nobel Prizes (Swedish: ) are awarded for Physics, Chemistry, Literature, Peace, and Physiology or Medicine. ... Paul Delos Boyer (born July 31, 1918) is an American biochemist. ... John Ernest Walker (born January 7, 1941) is an English chemist who won the Nobel Prize in Chemistry in 1997. ...

Heat production

Under certain conditions, protons can re-enter the mitochondrial matrix without contributing to ATP synthesis. This process is known as proton leak or mitochondrial uncoupling and is due to the facilitated diffusion of protons into the matrix. This process results in the unharnessed potential energy of the proton electrochemical gradient being released as heat. The process is mediated by a proton channel called thermogenin, or UCP1.^[10] Thermogenin is a 33kDa protein first discovered in 1973.^[11] Thermogenin is primarily found in brown adipose tissue, or brown fat, and is responsible for non-shivering thermogenesis. Brown adipose tissue is found in mammals and is at its highest levels in early life and in hibernating animals. In humans, brown adipose tissue is present at birth and decreases with age.^[10] facilitated difussion in cell membrane, showing ion channels and carrier proteins Facilitated diffusion (or facilitated transport) is a process of diffusion, a form of passive transport, where molecules diffuse across membranes, with the assistance of transport proteins. ... Thermogenin is a protein that helps generating heat in a cell by allowing protons to go back into the mitochondrion without having to go through ATP synthase. ... Thermogenin (also known as uncoupling protein 1, or UCP1) is an uncoupling protein found in the mitochondria of brown adipose tissue (BAT). ...

Storage of calcium ions

The concentrations of free calcium in the cell can regulate an array of reactions and is important for signal transduction in the cell. Mitochondria store calcium, a process that is one important event for the homeostasis of calcium in the cell. Release of this calcium back into the cells interior can initiate calcium spikes or waves. These events coordinate processes such as neurotransmitter release in nerve cells and release of hormones in endocrine cells. Calcium plays a vital role in the anatomy, physiology and biochemistry of organisms and of the cell, particularly in signal transduction pathways. ... Ca storages (in cell biology) are intracellular organelles, that constantly accumulate Ca2+ ions and release them on some cell events. ... In a neuron, synaptic vesicles, also called neurotransmitter vesicles, store the various neurotransmitters that are released during calcium-regulated exocytosis at the presynaptic terminal into the synaptic cleft of a synapse. ...

Mitochondrial dysfunction and disease

With their central place in cell metabolism, damage and dysfunction in mitochondria is an important factor in a wide range of human diseases. These diseases include schizophrenia, Bipolar disorder, dementia, Alzheimer's disease, Parkinson's disease, epilepsy, strokes, heart disease, retinitis pigmentosa and diabetes.^[12]^[13] The common thread linking these seemingly-unrelated conditions is cellular damage causing oxidative stress and the accumulation of reactive oxygen species. These oxidants then damage the mitochondrial DNA, resulting in mitochondrial dysfunction and cell death.^[13] For other uses, see Bipolar. ... For other uses, see Dementia (disambiguation). ... The Strokes are an American rock and roll band who formed in New York City and gained fame for their live shows. ... Heart disease is an umbrella term for a number of different diseases which affect the heart and as of 2007 it is the leading cause of death in the United States. ... Normal vision. ... This article is about the disease that features high blood sugar. ... Oxidative stress is a medical term for damage to animal or plant cells (and thereby the organs and tissues composed of those cells) caused by reactive oxygen species, which include (but are not limited to) superoxide, singlet oxygen, peroxynitrite or hydrogen peroxide. ... Reactive oxygen species (ROS) include oxygen ions, free radicals and peroxides both inorganic and organic. ...

Mutations in mitochondrial DNA can also be inherited, causing genetic disorders such as dominant optic atrophy, Friedreich's ataxia, hereditary spastic paraplegia, and Wilson's disease.^[14] Environmental influences may also interact with hereditary predispositions and cause mitochondrial disease; an example of this is the possible role of pesticide exposure in causing some individuals to develop Parkinson's disease.^[15]^[16] A genetic disorder is a disease caused by abnormalities in genes or chromosomes. ... Optic atrophy is a pathological term and somewhat misleading. ... Friedreichs ataxia is a rare autosomal recessive disorder caused by a mutation in Gene X25 that codes for frataxin, located on chromosome 9. ... Spastic paraplegia is a form of paraplegia defined by spasticity of the affected muscles, rather than paralysis. ... Wilsons disease or hepatolenticular degeneration is an autosomal recessive hereditary disease, with an incidence of about 1 in 30,000 in most parts of the world and a male preponderance. ... A cropduster spreading pesticide. ...

Origin

As mitochondria contain ribosomes and DNA, and are only formed by the division of other mitochondria, it is generally accepted that they were originally derived from endosymbiotic prokaryotes. Studies of mitochondrial DNA, which is often circular and employs a variant genetic code, show their ancestor, the so-called proto-mitochondrion, was a member of the Proteobacteria.^[17] In particular, the pre-mitochondrion was probably related to the rickettsias, although the exact position of the ancestor of mitochondria among the alpha-proteobacteria remains controversial. The endosymbiotic hypothesis suggests that mitochondria descended from specialized bacteria (probably purple non-sulfur bacteria) that somehow survived endocytosis by another species of prokaryote or some other cell type, and became incorporated into the cytoplasm. The ability of symbiont bacteria to conduct cellular respiration in host cells that had relied on glycolysis and fermentation would have provided a considerable evolutionary advantage. Similarly, host cells with symbiotic bacteria capable of photosynthesis would also have an advantage. In both cases, the number of environments in which the cells could survive would have been greatly expanded. It has been suggested that Proto-mitochondrion be merged into this article or section. ... An endosymbiont (also known as intracellular symbiont) is any organism that lives within cells of another organism, i. ... Mitochondrial DNA (some captions in German) Mitochondrial DNA (mtDNA) is the DNA located in organelles called mitochondria. ... For a non-technical introduction to the topic, see Introduction to Genetics. ... It has been suggested that this article or section be merged into Endosymbiotic theory. ... Orders Alpha Proteobacteria Caulobacterales - e. ... Families Rickettsiaceae Ehrlichiaceae Holosporaceae The Rickettsiales are an order of small proteobacteria. ... It has been suggested that Proto-mitochondrion be merged into this article or section. ... It has been suggested that Endocytic cycle be merged into this article or section. ... It has been suggested that Cytoplast be merged into this article or section. ... Glycolysis is a metabolic pathway by which a 6-carbon glucose (Glc) molecule is oxidized to two molecules of pyruvic acid (Pyr). ... The leaf is the primary site of photosynthesis in plants. ...

This relationship developed at least 2 billion years ago and mitochondria still show some signs of their ancient origin. Mitochondrial ribosomes in mammals are the 70S (bacterial) type, in contrast to the 80S ribosomes found elsewhere in the cell.^[18]. Figure 1: Ribosome structure indicating small subunit (A) and large subunit (B). ...

A few groups of unicellular eukaryotes lack mitochondria: the microsporidians, metamonads, and archamoebae.^[19] These groups appear as the most primitive eukaryotes on phylogenetic trees constructed using rRNA information, suggesting that they appeared before the origin of mitochondria. However, this is now known to be an artifact of long branch attraction — they are apparently derived groups and retain genes or organelles derived from mitochondria (e.g. mitosomes and hydrogenosomes).^[1] There are no primitively amitochondriate eukaryotes, and so the origin of mitochondria may have played a critical part in the development of eukaryotic cells. Subclasses Dihaplophasea Haplophasea Microsporidia are parasites of animals, now considered to be extremely reduced fungi. ... Classes & orders Eopharyngia Retortamonadida Diplomonadida Carpediemonas Parabasalia Anaeromonada Oxymonadida Trimastix The metamonads are a group of flagellate protozoa, including the retortamonads, diplomonads, and possibly the parabasalids and oxymonads as well. ... Genera Endolimax Entamoeba Mastigamoeba Mastigella Mastigina Pelomyxa Phreatamoeba The Archamoebae are a group of Amoebozoa distinguished by the absence of mitochondria. ... A phylogenetic tree is a tree showing the evolutionary interrelationships among various species or other entities that are believed to have a common ancestor. ... A non-coding RNA (ncRNA) is any RNA molecule that functions without being translated into a protein. ... Long branch attraction (LBA) is a phenomenon in phylogenetic analyses (most commonly those employing maximum parsimony) when rapidly evolving lineages are inferred to be closely related, regardless of their true evolutionary relationships. ... A mitosome is an organelle found in some unicellular eukaryotic organisms. ... A hydrogenosome is an organelle of ciliates, trichomonads and fungi. ...

Mitochondrial genome

One mitochondrion can contain 2-10 copies of its DNA.^[20] As in prokaryotes, there is a very high proportion of coding DNA, and an absence of repeats. Mitochondrial genes are transcribed as multigenic transcripts which are cleaved and polyadenylated to yield mature mRNAs. Not all necessary proteins, however, are encoded by the mitochondrial genome; most are coded by genes in the cell nucleus and imported to the mitochondrion.^[21] Unlike their nuclear cousins, mitochondrial genes are small, and many chromosomes are circular, conforming to the bacterial pattern. In humans, mitochondrial genes lack introns,^[21] yet other Eukaryotic mitochondrial DNA has 1-37 of them. Polyadenylation is the covalent linkage of a polyadenylyl moiety to a messenger RNA (mRNA) molecule. ... HeLa cells stained for DNA with the Blue Hoechst dye. ... Diagram of the location of introns and exons within a gene. ...

While slight variations on the standard code had been predicted earlier,^[22] none were discovered until 1979, when researchers studying human mitochondrial genes discovered they used an alternative code. Many slight variants have been discovered since,^[23] including various alternative mitochondrial codes,^[24] Further, the AUA, AUC, and AUU are each allowable start codons. // Mitochondrial genetics is the study of the genetics of the DNA contained in mitochondria. ...

Pseudo changes in the DNA genetic code are also seen due to the phenomenon of RNA editing that is common in mitochondria. In higher plants it was thought that CGG encoded for tryptophan and not arginine, however, it was discovered that the processed RNA from these genes does have the UGG codon, consistent with the universal genetic code. ^[25] // Introduction The term RNA editing describes those molecular processes in which the information content is altered in a RNA molecule through a chemical change in the base makeup. ... The term Universal Genetic Code, or Universal Code, is an old-fashioned name for the standard genetic code. ...

Mitochondrial genomes have many fewer genes than do the related eubacteria from which they are thought to be descended. Although some have been lost altogether, many have been transferred to the nucleus. This is thought to be relatively common over evolutionary time. A few organisms, such as the Cryptosporidium, actually have mitochondria which lack any DNA, presumably because all their genes have either been lost or transferred.^[26] In Cryptosporidium, the mitochondria have an altered ATP generation system that renders the parasite resistant to many classical mitochondrial inhibitors such as cyanide, azide, and atovaquone.^[26] Species Cryptosporidium bailey Cryptosporidium meleagridis Cryptosporidium muris Cryptosporidium parvum Cryptosporidium serpentis Cryptosporidium is a protozoan pathogen of the Phylum Apicomplexa and causes a diarrheal illness called cryptosporidiosis. ... The cyanide ion, CNâˆ’. From the top: 1. ... An azide is the N3- anion, the anion of hydrazoic acid or a reactive group in organic chemistry where a carbon substituent is attached as RN3. ... Atovaquone (Mepron) is a medication used to treat or prevent Pneumocystis carinii pneumonia. ...

Replication and gene inheritance

Mitochondria replicate their DNA and divide mainly in response to the energy needs of the cell; in other words, their growth and division is not linked to the cell cycle. When the energy needs of a cell are high, mitochondria grow and divide. When the energy use is low, mitochondria are destroyed or become inactive. At cell division, mitochondria are distributed to the daughter cells more or less randomly during the division of the cytoplasm. Mitochondria divide by binary fission similar to bacterial cell division. Unlike bacteria, however, mitochondria can also fuse with other mitochondria. The mitochondrial genome is the genetic material of the mitochondria. ... The cell cycle, or cell-division cycle, is the series of events that take place in a eukaryotic cell leading to its replication. ... It has been suggested that Cytoplast be merged into this article or section. ...

Mitochondrial genes are not inherited by the same mechanism as nuclear genes. At fertilization of an egg by a sperm, the egg nucleus and sperm nucleus each contribute equally to the genetic makeup of the zygote nucleus. In contrast, the mitochondria, and therefore the mitochondrial DNA, usually comes from the egg only. The sperm's mitochondria enters the egg, but are almost always destroyed and do not contribute their genes to the embryo.^[27] Paternal sperm mitochondria are marked with ubiquitin to select them for later destruction inside the embryo.^[28] The egg contains relatively few mitochondria, but it is these mitochondria that survive and divide to populate the cells of the adult organism. Mitochondria are, therefore, in most cases inherited down the female line. It has been suggested that Biparental zygote be merged into this article or section. ... Ubiquitin is a very conserved small regulatory protein that is ubiquitous in eukaryotes. ... For other uses, see Embryo (disambiguation). ...

This maternal inheritance of mitochondrial DNA is seen in most organisms, including all animals. However, mitochondria in some species can sometimes be inherited through the father. This is the norm among certain coniferous plants although not in pines and yew trees.^[29] It has been suggested to occur at a very low level in humans.^[30] In genetics, non-Mendelian inheritance is the passing on of a trait in a form other than through chromosomal inheritance. ... Orders & Families Cordaitales † Pinales Pinaceae - Pine family Araucariaceae - Araucaria family Podocarpaceae - Yellow-wood family Sciadopityaceae - Umbrella-pine family Cupressaceae - Cypress family Cephalotaxaceae - Plum-yew family Taxaceae - Yew family Vojnovskyales † Voltziales † The conifers, division Pinophyta, are one of 13 or 14 division level taxa within the Kingdom Plantae. ...

Uniparental inheritance means that there is little opportunity for genetic recombination between different lineages of mitochondria, although a single mitochondrion can contain 2-10 copies of its DNA.^[20] For this reason, mitochondrial DNA usually is thought of as reproducing by binary fission; what recombination that takes place is to maintain genetic integrity rather than to maintain diversity. However, there are several studies showing evidence of recombination in mitochondrial DNA. The enzymes necessary for recombination clearly are present in mammalian cells.^[31] Further, evidence suggests that animal mitochondria can undergo recombination.^[32] The data are a bit more controversial in humans, although, indirect evidence exists.^[33]^[34] If recombination does not occur, the whole mitochondrial DNA sequence represents a single haplotype, which makes it useful for studying the evolutionary history of populations. Genetic recombination is the process by which a strand of DNA is broken and then joined to the end of a different DNA molecule. ... Binary fission Binary fission is the form of asexual reproduction in single-celled organisms by which one cell divides into two cells of the same size, used by most prokaryotes. ... A haplotype is the genetic constitution of an individual chromosome. ...

The uniparental inheritance of mitochondria is thought to result in intragenomic conflict, such as seen in the petite mutant mitochondria of some yeast species. It is possible that the evolution of separate male and female sexes is a mechanism to resolve this organelle conflict. The selfish gene theory postulates that natural selection will increase the frequency of those genes whose phenotypic effects ensure their successful replication. ... Schematic of typical animal cell, showing subcellular components. ...

Use in population genetic studies

The near-absence of genetic recombination in mitochondrial DNA makes it a useful source of information for scientists involved in population genetics and evolutionary biology. Because all the mitochondrial DNA is inherited as a single unit, or haplotype, the relationships between mitochondrial DNA from different individuals can be represented as a gene tree. Patterns in these gene trees can be used to infer the evolutionary history of populations. The classic example of this is in human evolutionary genetics, where the molecular clock can be used to provide a recent date for mitochondrial Eve. This is often interpreted as strong support for a recent modern human expansion out of Africa. Another human example is the sequencing of mitochondrial DNA from Neanderthal bones. The relatively large evolutionary distance between the mitochondrial DNA sequences of Neanderthals and living humans has been interpreted as evidence for lack of interbreeding between Neanderthals and anatomically modern humans. // Mitochondrial genetics is the study of the genetics of the DNA contained in mitochondria. ... Genetic recombination is the process by which a strand of DNA is broken and then joined to the end of a different DNA molecule. ... Population genetics is the study of the distribution of and change in allele frequencies under the influence of the four evolutionary forces: natural selection, genetic drift, mutation, and migration. ... This article or section does not cite any references or sources. ... A haplotype is the genetic constitution of an individual chromosome. ... Fig. ... The molecular clock (based on the molecular clock hypothesis (MCH)) is a technique in genetics, which researchers use to date when two species diverged. ... Mitochondrial Eve (mt-mrca) is the name given by researchers to the woman who is the matrilineal most recent common ancestor (MRCA) for all living humans. ... Map of early human migrations according to mitochondrial population genetics In paleoanthropology, the recent single-origin hypothesis (RSOH, or Out-of-Africa model, or Replacement Hypothesis) is one of two accounts of the origin of anatomically modern humans, Homo sapiens. ... For other uses, see Neanderthal (disambiguation). ...

However, mitochondrial DNA only reflects the history of females in a population, and so may not give a representative picture of the history of the population as a whole. For example, if dispersal is primarily undertaken by males, this will not be picked up by mitochondrial studies. This can be partially overcome by the use of patrilineal genetic sequences, if they are available (in mammals the non-recombining region of the Y-chromosome provides such a source). More broadly, only studies that also include nuclear DNA can provide a comprehensive evolutionary history of a population; unfortunately, genetic recombination means that these studies can be difficult to analyze. The Y chromosome is one of the sex-determining chromosomes in humans and most other mammals (the other is the X chromosome). ... Nuclear DNA is DNA contained within a nucleus of eukaryotic organisms. ...

Fiction

Midi-chlorians (also spelled midi-clorians or midichlorians) are a fictional microorganism in the Star Wars universe, first mentioned in the prequel trilogy. ... Star Wars is an epic space opera saga and a fictional universe initially developed by George Lucas during the 1970s and expanded since that time. ... The Force is a binding, ubiquitous power that is the object of the Jedi and Sith monastic orders in the Star Wars universe. ... It has been suggested that Proto-mitochondrion be merged into this article or section. ... Madeleine LEngle (November 29, 1918 â€“ September 6, 2007)[1] was an American writer best known for her childrens books, particularly the Newbery Medal-winning A Wrinkle in Time and its sequels A Wind in the Door, A Swiftly Tilting Planet and Many Waters. ... A Wind in the Door is a 1973 novel by Madeleine LEngle. ... Hideaki Sena (ç€¬å ç§€æ˜Ž; Sena Hideaki) is a Japanese novelist; his prizewinning debut novel, Parasite Eve, was adapted into a popular horror role-playing game by Squaresoft. ... Parasite Eve ) is a survival horror console role-playing game developed and published by Square (now Square Enix). ...

References

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^ ^a ^b ^c Alberts, Bruce; Alexander Johnson, Julian Lewis, Martin Raff, Keith Roberts, Peter Walter (1994). Molecular Biology of the Cell. New York: Garland Publishing Inc.. ISBN 0-815-33218-1.
^ Voet, Donald; Judith G. Voet, Charlotte W. Pratt (2006). Fundamentals of Biochemistry, 2nd Edition. John Wiley and Sons, Inc., 547. ISBN 0-471-21495-7.
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^ Nicholls DG, Lindberg O (1973). "Brown-adipose-tissue mitochondria. The influence of albumin and nucleotides on passive ion permeabilities.". Eur. J. Biochem. 37: 523-530.
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^ Chinnery PF, Schon EA (2003). "Mitochondria". J. Neurol. Neurosurg. Psychiatr. 74 (9): 1188-99. PMID 12933917.
^ Sherer TB, Betarbet R, Greenamyre JT (2002). "Environment, mitochondria, and Parkinson's disease". The Neuroscientist : a review journal bringing neurobiology, neurology and psychiatry 8 (3): 192-7. PMID 12061498.
^ Gomez C, Bandez MJ, Navarro A (2007). "Pesticides and impairment of mitochondrial function in relation with the parkinsonian syndrome". Front. Biosci. 12: 1079-93. PMID 17127363.
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^ Crick, F. H. C. and Orgel, L. E. (1973) "Directed panspermia." Icarus 19:341-346. p. 344: "It is a little surprising that organisms with somewhat different codes do not coexist." (Further discussion at [1])
^ NCBI: "The Genetic Codes", Compiled by Andrzej (Anjay) Elzanowski and Jim Ostell
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External links

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Contents

Mitochondrion structure

Outer membrane

Intermembrane space

Inner membrane

Mitochondrial matrix

Mitochondrial functions

Energy conversion

Pyruvate: the citric acid cycle

NADH and FADH₂: the electron transport chain

Heat production

Storage of calcium ions

Mitochondrial dysfunction and disease

Origin

Mitochondrial genome

Replication and gene inheritance

Use in population genetic studies

Fiction

References

External links

See also

Contents

Mitochondrion structure GA_googleFillSlot("encyclopedia_square");

Outer membrane

Intermembrane space

Inner membrane

Mitochondrial matrix

Mitochondrial functions

Energy conversion

Pyruvate: the citric acid cycle

NADH and FADH2: the electron transport chain

Heat production

Storage of calcium ions

Mitochondrial dysfunction and disease

Origin

Mitochondrial genome

Replication and gene inheritance

Use in population genetic studies

Fiction

References

External links

See also

Mitochondrion structure

NADH and FADH₂: the electron transport chain