SUMMARY / RELATED TOPICS

Mitochondrion

The mitochondrion is a double-membrane-bound organelle found in most eukaryotic organisms. Some cells in some multicellular organisms may, lack them. A number of unicellular organisms, such as microsporidia and diplomonads, have reduced or transformed their mitochondria into other structures. To date, only two eukaryotes, Monocercomonoides and Henneguya salminicola, are known to have lost their mitochondria; the word mitochondrion comes from the Greek μίτος, mitos, "thread", χονδρίον, chondrion, "granule" or "grain-like". Mitochondria generate most of the cell's supply of adenosine triphosphate, used as a source of chemical energy. A mitochondrion is thus termed the powerhouse of the cell. Mitochondria are between 0.75 and 3 μm² in area but vary in size and structure. Unless stained, they are not visible. In addition to supplying cellular energy, mitochondria are involved in other tasks, such as signaling, cellular differentiation, 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, including mitochondrial disorders, cardiac dysfunction, heart failure and autism; the number of mitochondria in a cell can vary by organism and cell type. For instance, red blood cells have no mitochondria, whereas liver cells can have more than 2000; the organelle is composed of compartments. These compartments or regions include the outer membrane, the intermembrane space, the inner membrane, the cristae and matrix. Although most of a cell's DNA is contained in the cell nucleus, the mitochondrion has its own independent genome that shows substantial similarity to bacterial genomes. Mitochondrial proteins vary depending on the species. In humans, 615 distinct types of protein have been identified from cardiac mitochondria, whereas in rats, 940 proteins have been reported; the mitochondrial proteome is thought to be dynamically regulated. The first observations of intracellular structures that represented mitochondria were published in the 1840s.

Richard Altmann, in 1890, established them as cell organelles and called them "bioblasts". The term "mitochondria" was coined by Carl Benda in 1898. Leonor Michaelis discovered that Janus green can be used as a supravital stain for mitochondria in 1900. In 1904, Friedrich Meves, made the first recorded observation of mitochondria in plants in cells of the white waterlily, Nymphaea alba and in 1908, along with Claudius Regaud, suggested that they contain proteins and lipids. Benjamin F. Kingsbury, in 1912, first related them with cell respiration, but exclusively based on morphological observations. In 1913, particles from extracts of guinea-pig liver were linked to respiration by Otto Heinrich Warburg, which he called "grana". Warburg and Heinrich Otto Wieland, who had postulated a similar particle mechanism, disagreed on the chemical nature of the respiration, it was not until 1925, when David Keilin discovered cytochromes, that the respiratory chain was described. In 1939, experiments using minced muscle cells demonstrated that cellular respiration using one oxygen atom can form two adenosine triphosphate molecules, and, in 1941, the concept of the phosphate bonds of ATP being a form of energy in cellular metabolism was developed by Fritz Albert Lipmann.

In the following years, the mechanism behind cellular respiration was further elaborated, although its link to the mitochondria was not known. The introduction of tissue fractionation by Albert Claude allowed mitochondria to be isolated from other cell fractions and biochemical analysis to be conducted on them alone. In 1946, he concluded that cytochrome oxidase and other enzymes responsible for the respiratory chain were isolated to the mitochondria. Eugene Kennedy and Albert Lehninger discovered in 1948 that mitochondria are the site of oxidative phosphorylation in eukaryotes. Over time, the fractionation method was further developed, improving the quality of the mitochondria isolated, other elements of cell respiration were determined to occur in the mitochondria; 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 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. The popular term "powerhouse of the cell" was coined by Philip Siekevitz in 1957. In 1967, it was discovered. In 1968, methods were developed for mapping the mitochondrial genes, with the genetic and physical map of yeast mitochondrial DNA being completed in 1976. There are two hypotheses about the origin of mitochondria: autogenous; the endosymbiotic hypothesis suggests that mitochondria were prokaryotic cells, capable of implementing oxidative mechanisms that were not possible for eukaryotic cells. In the autogenous hypothesis, mitochondria were born by splitting off a portion of DNA from the nucleus of the eukaryotic cell at the time of divergence with the prokaryotes. Since mitochondria have many features in common with bacteria, the endosymbiotic hypothesis is more accepted. A mitoch

Georgia State Route 255

State Route 255 is a 19.7-mile-long S-shaped state highway located in the North Georgia mountains section of the U. S. state of Georgia. It travels through Habersham counties. SR 255 begins at an intersection with SR 115 east in White County; the route heads northeast, crosses over Blue Creek and travels through Batesville. Farther to the east, it passes New Blue Creek Cemetery and intersects SR 384, it crosses over Brasstown Creek shortly before it crosses over Chattahoochee River and enters Habersham County. Just after the county line, SR 255 crosses over Amys Creek and meets SR 17; the two highways share a concurrency. During the concurrency, SR 17/SR 255 intersect SR 255 Alt. and cross Maudlin Mill and Chickamauga Creeks before they reach Sautee Nacoochee. At Maudlin Mill Creek, they cross back into White County. There, SR 255 splits to the north. Just prior to curving to the northeast, the route crosses over Ben Creek, just after that curve, it crosses over Bean Creek and enters Chattahoochee-Oconee National Forest.

Northeast of Bean Creek, SR 255 intersects Sky Lake Road. Just after Sky Lake Road, the highway has a second crossing over Chickamauga Creek, it heads to the east, re-enters Habersham County, at the same time exiting the Chattahoochee-Oconee National Forest. A short while afterward, SR 255 has a second intersection with SR 255 Alt. Just northeast of that intersection, the route re-enters the Chattahoochee–Oconee National Forest; the highway heads north-northeast to meet its northern terminus, an intersection with SR 197 in Batesville. SR 255 travels through the historic Sautee Valley Historic District. No section of SR 255 is part of the National Highway System, a system of routes determined to be the most important for the nation's economy and defense. SR 255 was established in 1949 along an alignment from Sautee to Batesville. In 1953, a section from Sautee to just inside the Chattahoochee-Oconee National Forest was paved. By 1960, the entire route from Sautee to Batesville was paved, the section from the current western terminus to the southern intersection with SR 17 was paved.

It is unknown. State Route 255 Alternate is a 3.3-mile-long alternate route for SR 255. Its route is shorter and more direct than the mainline, bypasses the Sautee Valley Historic District, unincorporated community of Sautee; the highway is within Habersham County. None of SR 255 Alt., included as a part of the National Highway System, a system of routes determined to be the most important for the nation's economy and defense. SR 255 Alt. was established between 1960 and 1963 on the same routing as today. The entire route is in Habersham County. Georgia portal U. S. Roads portal

Calvert River

The Calvert River is a river in the Northern Territory of Australia. The headwaters rise on a plain between the Calvert Hills and China Wall and flow northward through uninhabited lands and pastoral leases such as Calvert Hills Station before discharging into the Gulf of Carpentaria 150 kilometres east of Borroloola, not far from the border with Queensland in the Gulf Coastal bioregion, it has a mean annual outflow of 1,000 gigalitres, Before reaching the sea it flows through the Australian Wildlife Conservancy’s Pungalina-Seven Emu Sanctuary. Fourteen tributaries feed the river including; the river’s catchment area is 10,033 square kilometres, wedged between the watersheds for the Robinson River to the west, Settlement Creek to east and the Nicholson River to the south. It contains the population was 103 in 2001, 45 % of whom are Aboriginal people; the river is not used for irrigation. The main economic activity is cattle grazing. A total of 34 species of fish are found in the river including.

The endangered Gulf snapping turtle has been found in the upper reaches of the river. The traditional owners of the area are the Garawa peoples; the river was named by Ludwig Leichhardt when on expedition from Queensland to Darwin in 1845. He named the river for another member of his party, John Calvert, in acknowledgement of his good service to the expedition. List of rivers of Northern Territory