Mitochondria generate most of the cell's supply of adenosine triphosphate (ATP), used as a source of chemical energy. A mitochondrion is thus termed the "powerhouse" of the cell. Mitochondria are commonly between 0.75 and 3 μm² in area but vary considerably in size and structure. Unless specifically stained, they are not visible. In addition to supplying cellular energy, mitochondria are involved in other tasks, such as signaling, cellular differentiation, and cell death, as well as maintaining control of the cell cycle and cell growth. Mitochondrial biogenesis is in turn temporally coordinated with these cellular processes. Mitochondria have been implicated in several human diseases, such as mitochondrial disorders, cardiac dysfunction, heart failure and autism.
Introduction
Mitochondrion
Mitochondrion | Introduction
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Mitochondria generate most of the cell's supply of adenosine triphosphate (ATP), used as a source of chemical energy. A mitochondrion is thus termed the "powerhouse" of the cell. Mitochondria are commonly between 0.75 and 3 μm² in area but vary considerably in size and structure. Unless specifically stained, they are not visible. In addition to supplying cellular energy, mitochondria are involved in other tasks, such as signaling, cellular differentiation, and cell death, as well as maintaining control of the cell cycle and cell growth. Mitochondrial biogenesis is in turn temporally coordinated with these cellular processes. Mitochondria have been implicated in several human diseases, such as mitochondrial disorders, cardiac dysfunction, heart failure and autism.
Mitochondrion | Introduction
The mitochondrion (, plural mitochondria) is a semi autonomous double-membrane-bound organelle found in most eukaryotic organisms. Some cells in some multicellular organisms may, however, lack mitochondria (for example, mature mammalian red blood cells). A number of unicellular organisms, such as microsporidia, parabasalids, and diplomonads, have also reduced or transformed their mitochondria into other structures. To date, only one eukaryote, "Monocercomonoides", is known to have completely lost its mitochondria, and one multicellular organism, "Henneguya salminicola", is known to have retained mitochondrion-related organelles in association with a complete loss of their mitochondrial genome. The word mitochondrion comes from the Greek , , "thread", and , , "granule" or "grain-like".
Mitochondrion | Introduction
Mitochondria (and related structures) are found in all eukaryotes (except two—the Oxymonad "Monocercomonoides" and "Henneguya salminicola"). Although commonly depicted as bean-like structures they form a highly dynamic network in the majority of cells where they constantly undergo fission and fusion. The population of all the mitochondria of a given cell constitutes the chondriome. Mitochondria vary in number and location according to cell type. A single mitochondrion is often found in unicellular organisms. Conversely, the chondriome size of human liver cells is large, with about 1000–2000 mitochondria per cell, making up 1/5 of the cell volume. The mitochondrial content of otherwise similar cells can vary substantially in size and membrane potential, with differences arising from sources including uneven partitioning at cell divisions, leading to extrinsic differences in ATP levels and downstream cellular processes.
Mitochondrion | Organization and distribution
The kinetoplast, after which the class is named, contains the mitochondrial genome and is a dense DNA-containing granule within the cell's single mitochondrion. The structure is made up of a network of concatenated circular DNA molecules and their related structural proteins along with DNA and RNA polymerases. The kinetoplast is found at the base of a cell's flagella and is associated to the flagellum basal body by a cytoskeletal structure.
Kinetoplastida | Mitochondrion and kinetoplast DNA
Mitochondria are organelles that synthesize ATP for the cell by metabolizing carbon-based macromolecules. The presence of deoxyribonucleic acid (DNA) in mitochondria and proteins, derived from mtDNA, suggest that this organelle may have been a prokaryote prior to its integration into the proto-eukaryote. Mitochondria are regarded as organelles rather than endosymbionts because mitochondria and the host cells share some parts of their genome, undergo mitosis simultaneously, and provide each other means to produce energy. Endomembrane system and nuclear membrane were hypothesized to have derived from the protomitochondria.
Symbiogenesis | Mitochondria
This membrane potential is ultimately what allows for the mitochondria to generate large quantities of ATP.
Intracellular pH | In organelles
Nearly all have mitochondria with tubular cristae.
Rhizaria | Introduction
A mitoplast is a mitochondrion that has been stripped of its outer membrane leaving the inner membrane intact.
Mitoplast | Introduction
In humans, brown adipose tissue is present at birth and decreases with age.
Mitochondrion | Heat production
The proto-mitochondrion is the hypothetical ancestral bacterial endosymbiont from which all mitochondria in eukaryotes are thought to descend.
Proto-mitochondrion | Introduction
The inner mitochondrial membrane is compartmentalized into numerous cristae, which expand the surface area of the inner mitochondrial membrane, enhancing its ability to produce ATP. For typical liver mitochondria, the area of the inner membrane is about five times as large as the outer membrane. This ratio is variable and mitochondria from cells that have a greater demand for ATP, such as muscle cells, contain even more cristae. Mitochondria within the same cell can have substantially different crista-density, the ones that are required to produce more energy, have much more crista-membrane surface. These folds are studded with small round bodies known as F particles or oxysomes.
Mitochondrion | Cristae
Megamitochondria is extremely large and abnormal shapes of mitochondria seen in hepatocytes in alcoholic liver disease and in nutritional deficiencies. It can be seen in conditions of hypertrophy in cell death.
Megamitochondria | Introduction
A published human mitochondrial DNA sequence revealed 16,569 base pairs encoding 37 genes: 22 tRNA, 2 rRNA, and 13 peptide genes. 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.
Mitochondrion | Matrix
Mitointeractome is a mitochondrial protein interactome database.
Mitointeractome | Introduction
In the mitochondria, metabolic processes such as cellular respiration occur. The cytoskeleton is made of fibers that support the structure of the cell and help the cell move.
Cell physiology | Eukaryotes
The mitochondrion and its genome is a remnant of the α-proteobacterial endosymbiont. The majority of the genes from the symbiont have been transferred to the nucleus. They make up most of the metabolic and energy-related pathways of the eukaryotic cell, while the information system is retained from archaea.
Eukaryote | Endomembrane system and mitochondria
The mitochondria can be found nestled between myofibrils of muscle or wrapped around the sperm flagellum. Often, they form a complex 3D branching network inside the cell with the cytoskeleton. The association with the cytoskeleton determines mitochondrial shape, which can affect the function as well: different structures of the mitochondrial network may afford the population a variety of physical, chemical, and signalling advantages or disadvantages. Mitochondria in cells are always distributed along microtubules and the distribution of these organelles is also correlated with the endoplasmic reticulum. Recent evidence suggests that vimentin, one of the components of the cytoskeleton, is also critical to the association with the cytoskeleton.
Mitochondrion | Organization and distribution
A mitochondrion contains DNA, which is organized as several copies of a single, usually circular chromosome. This mitochondrial chromosome contains genes for redox proteins, such as those of the respiratory chain. The CoRR hypothesis proposes that this co-location is required for redox regulation. The mitochondrial genome codes for some RNAs of ribosomes, and the 22 tRNAs necessary for the translation of mRNAs into protein. The circular structure is also found in prokaryotes. The proto-mitochondrion was probably closely related to "Rickettsia". However, the exact relationship of the ancestor of mitochondria to the alphaproteobacteria and whether the mitochondrion was formed at the same time or after the nucleus, remains controversial.
Mitochondrion | Origin and evolution
Organelles and bits of cytoplasm are sequestered and targeted for degradation by the lysosome for hydrolytic digestion by a process known as autophagy. Mitochondria metabolism leads to the creation of by-products that lead to DNA damage and mutations. Therefore, a healthy population of mitochondria is critical for the well-being of cells. Previously it was thought that targeted degradation of mitochondria was a stochastic event, but accumulating evidence suggest that mitophagy is a selective process. Generation of ATP by oxidative phosphorylation leads to the production of various reactive oxygen species (ROS) in the mitochondria, and submitochondrial particles. Formation of ROS as a mitochondrial waste product will eventually lead to cytotoxicity and cell death.
Mitophagy | Role
The functioning of mitochondria is studied in the field of bioenergetics. Functional differences between mitochondria from different species are studied by respirometry as an aspect of comparative physiology.
Respirometry | Basic research
Nanochondria are hypothetical nanomachines that are meant to live inside or with biological cells. They are named after mitochondria, due to their similarities in working inside the cell, and their reproduction.
Nanochondrion | Introduction
One of its arms is embedded in the inner membrane of the mitochondria, and the other is embedded in the organelle. The two arms are arranged in an L-shaped manner. The total molecular weight of the complex is 1MDa.
NDUFAF5 | Structure
Mitochondria are small organelles that lie in the cytoplasm of eukaryotic cells, such as those of humans. Their primary function is to provide energy to the cell. Mitochondria are thought to be reduced descendants of symbiotic bacteria that were once free living. One indication that mitochondria were once free living is that each contains a circular DNA, called mitochondrial DNA (mtDNA), whose structure is more similar to bacteria than eukaryotic organisms (see endosymbiotic theory). The overwhelming majority of a human's DNA is contained in the chromosomes in the nucleus of the cell, but mtDNA is an exception. An individual inherits his or her cytoplasm and the organelles contained by that cytoplasm exclusively from the maternal ovum (egg cell); sperm only pass on the chromosomal DNA, all paternal mitochondria are digested in the oocyte.
Haplogroup | Haplogroup formation
Outside the outer membrane there are small (diameter: 60Å) particles named sub-units of Parson.
Mitochondrion | Outer membrane
Some family members may be targeted to the mitochondria and even have a role in mitochondria.
TRNA-dihydrouridine synthase | Introduction
The Rickettsiales are widely believed to be the closest relatives to mitochondria. Based on the fact that the "Midichlorian" genes for the flagellum and for the cbb3 cytochrome oxidase were proven to be ancestral, the genes were inferred to have been present in the bacterium that established the symbiosis with the ancestor of the eukaryotic cell, which became the mitochondrion. Hence, sequencing the genome of "M. mitochondrii" allowed an improved reconstruction of the mitochondrion's hypothetical free-living ancestor: It was a motile bacterium able to survive in microaerophilic conditions. Both these characteristics may have played an important role in the beginning of the symbiosis between the eukaryotic cell and the mitochondrion.
Midichloria | "Midichloria" and the origin of mitochondria
g., mitosomes and hydrogenosomes). By this, mitochondria, hydrogenosomes, mitosomes, and related organelles as found in some loricifera (e. g. "Spinoloricus") and myxozoa (e. g. "Henneguya zschokkei") are together classified as MROs, mitochondrion-related organelles.
Mitochondrion | Origin and evolution
Mitochondria are dynamic organelles with the ability to fuse and divide (fission), forming constantly changing tubular networks in most eukaryotic cells. These mitochondrial dynamics, first observed over a hundred years ago are important for the health of the cell, and defects in dynamics lead to genetic disorders. Through fusion, mitochondria can overcome the dangerous consequences of genetic malfunction. The process of mitochondrial fusion involves a variety of proteins that assist the cell throughout the series of events that form this process.
Mitochondrial fusion | Introduction
Eukaryotic cells typically have mitochondrial DNA; however, mitochondria that lack their own DNA have been found in a marine parasitic dinoflagellate from the genus "Amoebophyra". This microorganism, "A. cerati", has functional mitochondria that lack a genome. In related species, the mitochondrial genome still has three genes, but in "A. cerati" only a single mitochondrial gene — the cytochrome c oxidase I gene ("cox1") — is found, and it has migrated to the genome of the nucleus.
Mitochondrion | Lack of mitochondrial DNA
Metalloendopeptidase OMA1, mitochondrial is an enzyme that in humans is encoded by the "OMA1" gene. As a metalloprotease, this protein is a substantial component of the quality control system in the inner membrane of mitochondria. Being activated by enzyme Bax and Bak, mitochondrial protease OMA1 promotes cytochrome c release which subsequently induces apoptosis.
OMA1 | Introduction
A mitochondrion contains outer and inner membranes composed of phospholipid bilayers and proteins. The two membranes have different properties. Because of this double-membraned organization, there are five distinct parts to a mitochondrion. They are: Mitochondria stripped of their outer membrane are called mitoplasts.
Mitochondrion | Structure
In mammalian cells, formation of these linkage sites are important for some cellular events including:
Mitochondria associated membranes | Role
This high amount of mitochondria is reported to be a result of mutations in the mitochondrial DNA. Some scientists have identified these mutations as deletions in the mitochondrial DNA of Hürthle cells found in neoplasms and Hashimoto's thyroiditis.
Hürthle cell | Histology
The MBU is the home of several freely-accessible scientific web-resources: MitoMiner - a mitochondrial proteomics database that provides information on cellular localisation, function and species & tissue specific expression The Integrated Mitochondrial Protein Index (IMPI) - a list of all the genes and proteins that make up the mammalian mitochondrion
MRC Mitochondrial Biology Unit | Resources
The MAM is a critical signaling, metabolic, and trafficking hub in the cell that allows for the integration of ER and mitochondrial physiology. Coupling between these organelles is not simply structural but functional as well and critical for overall cellular physiology and homeostasis. The MAM thus offers a perspective on mitochondria that diverges from the traditional view of this organelle as a static, isolated unit appropriated for its metabolic capacity by the cell. Instead, this mitochondrial-ER interface emphasizes the integration of the mitochondria, the product of an endosymbiotic event, into diverse cellular processes. Recently it has also been shown, that mitochondria and MAM-s in neurons are anchored to specialised intercellular communication sites (so called somatic-junctions).
Mitochondrion | Perspective
The oocyte receives mitochondria from maternal cells, which will go on to control embryonic metabolism and apoptotic events. The partitioning of mitochondria is carried out by a system of microtubules that will localize mitochondria throughout the oocyte. In certain organisms, such as mammals, paternal mitochondria brought to the oocyte by the spermatozoon are degraded through the attachment of ubiquitinated proteins. The destruction of paternal mitochondria ensures the strictly maternal inheritance of mitochondria and mitochondrial DNA or mtDNA.
Oocyte | Mitochondria
Supporting this fact, about five times more mitochondria are present in the PNP axoplasm of large peripheral axons than in the corresponding internodal regions of these fibers.
Node of Ranvier | Paranode regulation via mitochondria accumulation
The diplomonads (Greek for "two units") are a group of flagellates, most of which are parasitic. They include "Giardia lamblia", which causes giardiasis in humans. They are placed among the metamonads, and appear to be particularly close relatives of the retortamonads. Most diplomonads are double cells: they have two nuclei, each with four associated flagella, arranged symmetrically about the body's main axis. Like the retortamonads, they lack both mitochondria and Golgi apparatuses. However, they are now known to possess modified mitochondria, in the case of "G. lamblia", called mitosomes. These are not used in ATP synthesis the way mitochondria are, but are involved in the maturation of iron-sulfur proteins.
Diplomonad | Introduction
"G. lamblia" primarily generates its energy by breaking down glucose via glycolysis as well as the arginine dihydrolase pathway. It is unable to synthesize nucleotides on its own, instead salvaging them from its host. Synthesis of iron-sulfur clusters is done in a double-membrane-bound compartment called the mitosome, which is likely a remnant of mitochondria. Each cell contains 25 to 100 mitosomes divided into two categories: peripheral mitosomes which are scattered throughout the cell, and central mitosomes which gather at the center of the cell for unknown reasons. Like in mitochondria, proteins with a certain peptide signal sequence are trafficked to and imported into the mitosome.
Giardia duodenalis | Metabolism
The ability for a mitochondrion to self-replicate is rooted in its evolutionary history. It is commonly thought that mitochondria descend from cells that formed endosymbiotic relationships with α-protobacteria, they have their own genome for replication. However, recent evidence suggests that mitochondria may have evolved without symbiosis. The mitochondrion is a key regulator of the metabolic activity of the cell, and is also an important organelle in both production and degradation of free radicals. It is postulated that higher mitochondrial copy number (or higher mitochondrial mass) is protective for the cell. Mitochondria are produced from the transcription and translation of genes both in the nuclear genome and in the mitochondrial genome.
Mitochondrial biogenesis | Background
Molecular and biochemical evidence suggests that mitochondria are related to Rickettsiales proteobacteria (in particular, the SAR11 clade, or close relatives), and that chloroplasts are related to nitrogen-fixing filamentous cyanobacteria.
Symbiogenesis | From endosymbionts to organelles
Mitochondria are organelles found in all but one eukaryote. Mitochondria provide energy to the eukaryote cell by converting sugars into ATP. They have two surrounding membranes, each a phospholipid bi-layer; the inner of which is folded into invaginations called cristae where aerobic respiration takes place. The outer mitochondrial membrane is freely permeable and allows almost anything to enter into the intermembrane space while the inner mitochondrial membrane is semi permeable so allows only some required things into the mitochondrial matrix. Mitochondria contain their own DNA, which has close structural similarities to bacterial DNA, and which encodes rRNA and tRNA genes that produce RNA which is closer in structure to bacterial RNA than to eukaryote RNA.
Eukaryote | Mitochondria and plastids
They localize to the cytosol as well as the mitochondrion and peroxisome.
Isocitrate dehydrogenase | Introduction
Mitochondria and other membranous organelles are normally enriched in the PNP region of peripheral myelinated axons, especially those large caliber axons. The actual physiological role of this accumulation and factors that regulate it are not understood; however, it is known that mitochondria are usually present in areas of the cell that expresses a high energy demand. In these same regions, they are also understood to contain growth cones, synaptic terminals, and sites of action potential initiation and regeneration, such as the nodes of Ranvier. In the synaptic terminals, mitochondria produce the ATP needed to mobilize vesicles for neurotransmission. In the nodes of Ranvier, mitochondria serve as an important role in impulse conduction by producing the ATP that is essential to maintain the activity of energy-demanding ion pumps.
Node of Ranvier | Paranode regulation via mitochondria accumulation
The first high-resolution electron micrographs appeared in 1952, replacing the Janus Green stains as the preferred way of visualizing the mitochondria. This led to a more detailed analysis of the structure of the mitochondria, including confirmation that they were surrounded by a membrane. It also showed a second membrane inside the mitochondria that folded up in ridges dividing up the inner chamber and that the size and shape of the mitochondria varied from cell to cell.
Mitochondrion | History of discovery and research
(The more related two species are, the more mtDNA/RNA mutations will be the same in their mitochondrial genome). Using these techniques, it is estimated that the first mitochondria arose around 1.5 billion years ago. A generally accepted hypothesis is that mitochondria originated as an aerobic prokaryote in a symbiotic relationship within an anaerobic eukaryote.
Human mitochondrial genetics | Genetic code variants
RDH13 is localized in the mitochondria, which is different from the other members of this family, as they localize to the endoplasmic reticulum. The exact sequence targeting RDH13 to the mitochondria remains to be established.
RDH13 | Function
Mitochondria divide by binary fission, similar to bacterial cell division. The regulation of this division differs between eukaryotes. In many single-celled eukaryotes, their growth and division are linked to the cell cycle. For example, a single mitochondrion may divide synchronously with the nucleus. This division and segregation process must be tightly controlled so that each daughter cell receives at least one mitochondrion. In other eukaryotes (in mammals for example), mitochondria may replicate their DNA and divide mainly in response to the energy needs of the cell, rather than in phase with the cell cycle. When the energy needs of a cell are high, mitochondria grow and divide.
Mitochondrion | Replication and inheritance
Mitochondria contain their own genome, an indication that they are derived from bacteria through endosymbiosis. However, the ancestral endosymbiont genome has lost most of its genes so that the mitochondrial genome (mitogenome) is one of the most reduced genomes across organisms. The human mitochondrial genome is a circular DNA molecule of about 16 kilobases. It encodes 37 genes: 13 for subunits of respiratory complexes I, III, IV and V, 22 for mitochondrial tRNA (for the 20 standard amino acids, plus an extra gene for leucine and serine), and 2 for rRNA. One mitochondrion can contain two to ten copies of its DNA.
Mitochondrion | Genome
The majority of mitochondrial protein comes from the nuclear genome, while the mitochondrial genome encodes parts of the electron transport chain along with mitochondrial rRNA and tRNA. Mitochondrial biogenesis increases metabolic enzymes for glycolysis, oxidative phosphorylation and ultimately a greater mitochondrial metabolic capacity. However, depending on the energy substrates available and the REDOX state of the cell, the cell may increase or decrease the number and size of mitochondria. Critically, mitochondrial numbers and morphology vary according to cell type and context-specific demand, whereby the balance between mitochondrial fusion/fission regulates mitochondrial distribution, morphology, and function.
Mitochondrial biogenesis | Background
The mitochondria in a eukaryotic cell utilize fuels to produce energy in the form of adenosine triphosphate (ATP). This process involves storing energy as a proton gradient, also known as the proton motive force (PMF), across the mitochondrial inner membrane. This energy is used to synthesize ATP when the protons flow across the membrane (down their concentration gradient) through the ATP synthase enzyme; this is known as chemiosmosis. In endotherms, body heat is maintained by signaling the mitochondria to allow protons to run back along the gradient without producing ATP (proton leak). This can occur since an alternative return route for the protons exists through an uncoupling protein in the inner membrane.
Brown adipose tissue | Function
While there have been significant increases in mitochondria found in tissues where PGC-1α is overexpressed, as the cofactor interacts with these key transcription factors, knockout mice with disrupted PGC-1α are still viable and show normal mitochondrial abundance. Thus, PGC-1α is not required for normal development of mitochondria in mice, but when put under physiological stress, these mice exhibit diminished tolerance compared to mice with normal levels of PGC-1α. Similarly, in knockout mice with disrupted PGC-1β, the mice showed mostly normal levels of mitochondrial function with decreased ability to adapt to physiological stress. However, a double knockout experiment of PGC-1α/β created mice that died mostly within 24 hours by defects in mitochondrial maturation of cardiac tissue.
Mitochondrial biogenesis | Regulation
Mitochondrial diseases are a group of disorders caused by dysfunctional mitochondria, the organelles that generate energy for the cell. Mitochondria are found in every cell of the human body except red blood cells, and convert the energy of food molecules into the ATP that powers most cell functions. Mitochondrial diseases take on unique characteristics both because of the way the diseases are often inherited and because mitochondria are so critical to cell function. A subclass of these diseases that have neuromuscular symptoms are sometimes called mitochondrial myopathies.
Mitochondrial disease | Introduction
Endosymbiotic theory for the origin of mitochondria suggests that the proto-eukaryote engulfed a protomitochondria, and this endosymbiont became an organelle.
Symbiogenesis | Endosymbiosis of Protomitochondria
Mitochondria are sometimes described as "cellular power plants" because they generate most of the cell's supply of adenosine triphosphate (ATP), a source of chemical energy. Reactive oxygen species (ROS) have been regarded as unwanted by-products of oxidative phosphorylation in mitochondria by the proponents of the free-radical theory of aging promoted by Denham Harman. The free-radical theory suggests that the use of compounds which inactivate ROS, such as antioxidants, would lead to a reduction of oxidative stress and thereby produce an increase in lifespan. ROS may perform an essential and potentially lifespan-promoting role as redox signaling molecules which transduce signals from the mitochondrial compartment to other compartments of the cell.
Hormesis | Mitochondria
The ACADM enzyme functions in mitochondria, the energy-producing centers within cells. It is found in the mitochondria of several types of tissues, particularly the liver.
ACADM | Introduction
Around this time, the first proto-mitochondrion was formed. A bacterial cell related to today's "Rickettsia", which had evolved to metabolize oxygen, entered a larger prokaryotic cell, which lacked that capability. Perhaps the large cell attempted to digest the smaller one but failed (possibly due to the evolution of prey defenses). The smaller cell may have tried to parasitize the larger one. In any case, the smaller cell survived inside the larger cell. Using oxygen, it metabolized the larger cell's waste products and derived more energy. Part of this excess energy was returned to the host. The smaller cell replicated inside the larger one.
History of Earth | Emergence of eukaryotes
The matrix is the space enclosed by the inner membrane. It contains about 2/3 of the total proteins in a mitochondrion. 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, 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. The DNA molecules are packaged into nucleoids by proteins, one of which is TFAM. Mitochondria have their own genetic material, and the machinery to manufacture their own RNAs and proteins ("see: protein biosynthesis").
Mitochondrion | Matrix
Due to its lipophilic properties, SkQ-substances can penetrate the lipid bilayer. The transportation is caused by the electrical potential due to the presence of a positive charge in SkQ. Mitochondria are the only intracellular organelles with a negative charge. Therefore, SkQ effectively penetrates and accumulates there. The accumulation coefficient can be estimated using the Nernst equation. To do this, we must take into account that the potential of the plasma membrane of the cell is about 60 mV (the cytoplasm has a negative charge), and the potential of the mitochondrial membrane is about 180 mV (the matrix has a negative charge).
SkQ | Penetration into the mitochondria
While several NCBI GEO profiles examining various factors on gene expression show that C10orf67 is expressed in varying levels in different cancer tissues, the mitochondrial localization may yield some insight as to a clinical function. Mitochondria have been shown to have some influence in cell proliferation. Given the high energy demand from cell proliferation, there have been several hypotheses that the mitochondria may play a role in the cell cycle and that C10orf67, being localized to the mitochondria, may have a hand in this as well.
C10orf67 | Cancer
For typical liver mitochondria, the area of the inner membrane is about 5 times as large as the outer membrane due to cristae. This ratio is variable and mitochondria from cells that have a greater demand for ATP, such as muscle cells, contain even more cristae. Cristae membranes are studded on the matrix side with small round protein complexes known as F particles, the site of proton-gradient driven ATP synthesis. Cristae affect overall chemiosmotic function of mitochondria.
Inner mitochondrial membrane | Cristae
The formation of autophagosomes through the coordination of ATG (autophagy-related) proteins and the vesicular trafficking by MAM.
Mitochondria associated membranes | Regulation of <a href="autophagy">autophagy</a> and <a href="mitophagy">mitophagy</a>
The genome of C. Reinhardtii is significant for mitochondrial study as it is one species where the genes for 6 of the 13 proteins encoded for the mitochondria are found in the nucleus of the cell, leaving 7 in the mitochondria. In all other species these genes are present only in the mitochondria and are unable to be allotopically expressed. This is significant for the testing and development of therapies for genetic mitochondrial diseases.
Chlamydomonas reinhardtii | Mitochondrial Significance
In the mitochondrion, the matrix is the space within the inner membrane. The word "matrix" stems from the fact that this space is viscous, compared to the relatively aqueous cytoplasm. The mitochondrial matrix contains the mitochondria's DNA, ribosomes, soluble enzymes, small organic molecules, nucleotide cofactors, and inorganic ions. The enzymes in the matrix facilitate reactions responsible for the production of ATP, such as the citric acid cycle, oxidative phosphorylation, oxidation of pyruvate, and the beta oxidation of fatty acids. The composition of the matrix based on its structures and contents produce an environment that allows the anabolic and catabolic pathways to proceed favorably for.
Mitochondrial matrix | Introduction
It works as a mitochondrial oxidative phosphorylation uncoupler, disrupting the mitochondrial electron transport chain. This stops the mitochondria from producing adenosine triphosphate, releasing energy as heat.
Thermogenics | Introduction
Between protein-coding regions, tRNAs are present. During transcription, the tRNAs acquire their characteristic L-shape that gets recognized and cleaved by specific enzymes. Mitochondrial tRNA genes have different sequences from the nuclear tRNAs but lookalikes of mitochondrial tRNAs have been found in the nuclear chromosomes with high sequence similarity.
Mitochondrion | Genome
In a few cases, some mitochondria or a mitochondrion from the sperm cell enters the oocyte but paternal mitochondria are actively decomposed.
Human mitochondrial genetics | Inheritance patterns
Despite these marked differences between the cytoplasmic and mitochondrial form, experimental analysis has shown that the cell is quickly capable of moving cytoplasmic HSP60 into the mitochondria if environmental conditions demand a higher presence of mitochondrial HSP60.
HSP60 | Cytoplasmic vs mitochondrial HSP60
The inner membrane of mitochondria is similar in lipid composition to the membrane of bacteria. This phenomenon can be explained by the endosymbiont hypothesis of the origin of mitochondria as prokaryotes internalized by a eukaryotic host cell. In pig heart mitochondria, phosphatidylethanolamine makes up the majority of the inner mitochondrial membrane at 37.0% of the phospholipid composition. Phosphatidylcholine makes up about 26.5%, cardiolipin 25.4%, and phosphatidylinositol 4.5%. In "S. cerevisiae" mitochondria, phosphatidylcholine makes up 38.4% of the IMM, phosphatidylethanolamine makes up 24.0%, phosphatidylinositol 16.2%, cardiolipin 16.1%, phosphatidylserine 3.8%, and phosphatidic acid 1.5%. In the inner mitochondrial membrane, the protein-to-lipid ratio is 80:20, in contrast to the outer membrane, which is 50:50.
Inner mitochondrial membrane | Composition
The trematode mitochondrial code (translation table 21) is a genetic code found in the mitochondria of Trematoda.
Trematode mitochondrial code | Introduction
By the endosymbiosis theory, which gained acceptance around the 1970s, the mitochondrion, as a major energy factory of the cell, was previously a free-living prokaryote that invaded a eukaryotic cell. Under this theory, symbiotic organelles gradually transferred their genes to the eukaryotic genome, implying that mtDNA was gradually integrated into the nuclear genome. Despite the metabolic alterations and functional adaptations in the host eukaryotes, circular mitochondrial DNA is contained within the organelles. Containing 37 genes, mitochondrial DNA has an essential role in the production of necessary compounds, such as required enzymes for the proper function of mitochondria. Specifically, it has been suggested that certain genes (such as the genes for cytochrome oxidase subunits I and II) within the organelle are necessary to regulate redox balance throughout membrane-associated electron transport chains.
NUMT | Brief History of NUMT
These are not simple random folds but rather invaginations of the inner membrane, which can affect overall chemiosmotic function. One recent mathematical modeling study has suggested that the optical properties of the cristae in filamentous mitochondria may affect the generation and propagation of light within the tissue.
Mitochondrion | Cristae
Of note, the arthropod mitochondrial genetic code has undergone parallel evolution within a phylum, with some organisms uniquely translating AGG to lysine.
Mitochondrion | Alternative genetic code
It is suggested that mitochondrial degradation proceeds through at least two redundant pathways besides that triggered by lipoxygenase-dependent formation of 13("S")-HpODE- and 13("S")-HODE-bound phospholipids viz., mitochondrial digestion by autophagy and mitochondrial exocytosis. In all events, formation of 13("S")-HODE bound to phospholipid in mitochondrial membranes is one pathway by which they become more permeable and thereby subject to degradation and, as consequence of their release of deleterious elements, to cause cell injury.
13-Hydroxyoctadecadienoic acid | Involvement in mitochondria degradation
The genome of "M. mitochondrii" has been sequenced by an international scientific consortium formed by researchers at the University of Milan, the University of Sydney, the University of Valencia, the University of Pavia, and the University of Milan Bicocca. The genome is 1.2 Mb, and it is, for most characteristics, very similar to the genomes of the other Rickettsiales, with two notable exceptions; the genome of "M. mitochondrii" contains the gene sets for the synthesis of the flagellum and of a cytochrome cbb3 oxidase.
Midichloria | Genome
Conventional TEM has also some technical limitations in verifying mitochondrial division. Cryo-electron tomography was recently used to visualize mitochondrial division in frozen hydrated intact cells. It revealed that mitochondria divide by budding. An individual's mitochondrial genes are not inherited by the same mechanism as nuclear genes. Typically, the mitochondria are inherited from one parent only. In humans, when an egg cell is fertilized 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 come from the egg only. The sperm's mitochondria enter the egg, but do not contribute genetic information to the embryo.
Mitochondrion | Replication and inheritance
Vitamin C accumulates in mitochondria, where most of the free radicals are produced, by entering as DHA through the glucose transporters, GLUT10. Ascorbic acid protects the mitochondrial genome and membrane.
Dehydroascorbic acid | Transport to mitochondria
It is important to keep the dysfunctional mitochondria regulated, because all of these traits could be induced by mitochondrial dysfunction and can induce cell death. Disorders in energy creation by mitochondria can cause cellular degeneration, like those seen in the substantia nigra.
Mitophagy | Parkinson's disease
It was predicted that the location of C1orf21 is in the nucleus with 62.2% certainty. The mitochondria was predicted at 17.4%: mitochondrial, while the cytoskeleton, and vascular system at 4.3%.
C1orf21 | Subcellular location
The looped mitochondria takes up a large amount of the internal volume of the cell and contain the kinetoplast, a large network of circular DNA.
Bodo (excavate) | Morphology
The mitochondrial intermembrane space is the space between the outer membrane and the inner membrane. It is also known as perimitochondrial space. Because the outer membrane is freely permeable to small molecules, the concentrations of small molecules, such as ions and sugars, in the intermembrane space is the same as in the cytosol. However, large proteins must have a specific signaling sequence to be transported across the outer membrane, so the protein composition of this space is different from the protein composition of the cytosol. One protein that is localized to the intermembrane space in this way is cytochrome c.
Mitochondrion | Intermembrane space
The relationship between cellular proliferation and mitochondria has been investigated using cervical cancer HeLa cells. Tumor cells require an ample amount of ATP (Adenosine triphosphate) in order to synthesize bioactive compounds such as lipids, proteins, and nucleotides for rapid cell proliferation. The majority of ATP in tumor cells is generated via the oxidative phosphorylation pathway (OxPhos). Interference with OxPhos have shown to cause cell cycle arrest suggesting that mitochondria play a role in cell proliferation. Mitochondrial ATP production is also vital for cell division and differentiation in infection in addition to basic functions in the cell including the regulation of cell volume, solute concentration, and cellular architecture.
Mitochondrion | Cellular proliferation regulation
The MRC Mitochondrial Biology Unit (formerly the MRC Dunn Human Nutrition Unit) is a department of the School of Clinical Medicine at the University of Cambridge, funded through a strategic partnership between the Medical Research Council and the University. It is located at the Addenbrooke’s Hospital / Cambridge Biomedical Campus site in Cambridge, England. The unit is concerned with the study of the mitochondrion, as this organelle has a varied and critical role in many aspects of eukaryotic metabolism and is implicated in many metabolic, degenerative, and age-related human diseases.
MRC Mitochondrial Biology Unit | Introduction
The ability of these bacteria to conduct respiration in host cells that had relied on glycolysis and fermentation would have provided a considerable evolutionary advantage. This symbiotic relationship probably developed 1.7 to 2 billion years ago. A few groups of unicellular eukaryotes have only vestigial mitochondria or derived structures: the microsporidians, metamonads, and archamoebae. These groups appear as the most primitive eukaryotes on phylogenetic trees constructed using rRNA information, which once suggested that they appeared before the origin of mitochondria. However, this is now known to be an artifact of long-branch attraction—they are derived groups and retain genes or organelles derived from mitochondria (e.
Mitochondrion | Origin and evolution
Clustered mitochondria (cluA/CLU1) homolog is a protein in humans that is encoded by the CLUH gene.
CLUH | Introduction
The "Thraustochytrium" mitochondrial code (translation table 23) is a genetic code found in the mitochondria of labyrinthulid "Thraustochytrium aureum". The mitochondrial genome was sequenced by the Organelle Genome Megasequencing Program.
Thraustochytrium mitochondrial code | Introduction
Kiss-and-run fusion provides a better mechanism to control mitochondrial bioenergetics than full fusion.
Kiss-and-run fusion | Mitochondria
Upon entry into mitochondria, the molecules are broken down by a proteolytic reaction to yield mature frataxin.
Frataxin | Structure
Because of their role in metabolism, mitochondria are very susceptible to ROS damage. Damaged mitochondria cause a depletion in ATP and a release of cytochrome "c", which leads to activation of caspases and onset of apoptosis. Mitochondrial damage is not caused solely by oxidative stress or disease processes; normal mitochondria will eventually accumulate oxidative damage hallmarks overtime, which can be deleterious to mitochondria as well as to the cell. These faulty mitochondria can further deplete the cell of ATP, increase production of ROS, and release proapoptopic proteins such as caspases. Because of the danger of having damaged mitochondria in the cell, the timely elimination of damaged and aged mitochondria is essential for maintaining the integrity of the cell.
Mitophagy | Role
It is also essential for normal mitochondrial function.
C19orf70 | Function
The differences in tissue distribution suggest that the two mitochondrial carbonic anhydrases evolved to assume different physiologic roles.
Carbonic anhydrase 5B, mitochondrial | Introduction
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. 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). This process is called chemiosmosis, and was first described by Peter Mitchell, who was awarded the 1978 Nobel Prize in Chemistry for his work.
Mitochondrion | NADH and FADH: the electron transport chain
Power, Sex, Suicide: Mitochondria and the Meaning of Life is a 2005 popular science book by Nick Lane of University College London, which argues that mitochondria are central to questions of the evolution of multicellularity, the evolution of sexual reproduction, and to the process of senescence. Amongst the theories advanced in the book, Lane endorses the hydrogen hypothesis for the formation of the eukaryotic cell, whereby mitochondria are the original defining characteristic of the structure. He argues that the event was an exceedingly improbable one and questions the likelihood of it having happened elsewhere in the Universe. He also suggests that the necessity for genetic compatibility between mitochondrial and nuclear DNA lies behind the differentiation of biological genders, ensuring that only one sexual partner contributes mitochondrial DNA to offspring.
Power, Sex, Suicide | Introduction
Mitochondria are organelles which function to transform energy as a result of cellular respiration. Chloroplasts are organelles which function to produce sugars via photosynthesis in plants and algae. The genes located in mitochondria and chloroplasts are very important for proper cellular function. The mitochondrial DNA and other extranuclear types of DNA replicate independently of the DNA located in the nucleus, which is typically arranged in chromosomes that only replicate one time preceding cellular division. The extranuclear genomes of mitochondria and chloroplasts however replicate independently of cell division. They replicate in response to a cell's increasing energy needs which adjust during that cell's lifespan.
Extranuclear inheritance | Organelles
Given the role of mitochondria as the cell's powerhouse, there may be some leakage of the high-energy electrons in the respiratory chain to form reactive oxygen species. This was thought to result in significant oxidative stress in the mitochondria with high mutation rates of mitochondrial DNA (mtDNA). Hypothesized links between aging and oxidative stress are not new and were proposed in 1956, which was later refined into the mitochondrial free radical theory of aging. A vicious cycle was thought to occur, as oxidative stress leads to mitochondrial DNA mutations, which can lead to enzymatic abnormalities and further oxidative stress. A number of changes can occur to mitochondria during the aging process.
Mitochondrion | Possible relationships to aging
This is called "serial endosymbiosis"—an early eukaryote engulfing the mitochondrion ancestor, and some descendants of it then engulfing the chloroplast ancestor, creating a cell with both chloroplasts and mitochondria.
Chloroplast | Primary endosymbiosis
Moreover, PNKD-L localizes to the cell membrane, PNKD-S to the cytoplasm and nucleus, and PNKD-M to the mitochondrion.
PNKD | Structure
Sarcosine dehydrogenase, mitochondrial is an enzyme that in humans is encoded by the "SARDH" gene.
SARDH | Introduction
A critical role for the ER in calcium signaling was acknowledged before such a role for the mitochondria was widely accepted, in part because the low affinity of Ca channels localized to the outer mitochondrial membrane seemed to contradict this organelle's purported responsiveness to changes in intracellular Ca flux. But the presence of the MAM resolves this apparent contradiction: the close physical association between the two organelles results in Ca microdomains at contact points that facilitate efficient Ca transmission from the ER to the mitochondria. Transmission occurs in response to so-called "Ca puffs" generated by spontaneous clustering and activation of IP3R, a canonical ER membrane Ca channel.
Mitochondrion | Calcium signaling
The motor/adaptor complex is regulated by calcium ion levels. At high concentrations, calcium ions arrest mitochondrial transport by binding Miro, causing the complex to detach from the organelle. Considering that physiological factors such as activation of glutamate receptors in dendrites, action potentials in axons, and neuromodulators may elevate calcium ion levels, this regulatory mechanism likely serves to keep mitochondria in such areas to provide calcium ion buffering and active export and, thus, maintain homeostasis.
RHOT2 | Function