In addition, it obtains information from other U. While the preceding agencies both collect and analyze information, some like the U. State Department's Bureau of Intelligence and Research are purely analytical agencies.
ATP synthasewhich generates ATP in the matrix Specific transport proteins that regulate metabolite passage into and out of the matrix Protein import machinery Mitochondrial fusion and fission protein It contains more than different polypeptidesand has a very high protein-to-phospholipid ratio more than 3: This phospholipid was originally discovered in cow hearts inand is usually characteristic of mitochondrial and bacterial plasma membranes.
Almost all ions and molecules require special membrane transporters to enter or exit the matrix. Proteins are ferried into the matrix via the translocase of the inner membrane TIM complex or via Oxa1. Cristae Cross-sectional image of cristae in rat liver mitochondrion to demonstrate the likely 3D structure and relationship to the inner membrane Main article: Cristae The inner mitochondrial membrane is compartmentalized into numerous cristaewhich 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.
These folds are studded with small round bodies known as F1 particles or oxysomes. These are not simple random folds but rather invaginations of the inner membrane, which can affect overall chemiosmotic function.
Mitochondrial matrix The matrix is the space enclosed by the inner membrane. The matrix contains a highly concentrated mixture of hundreds of enzymes, special mitochondrial ribosomestRNAand several copies of the mitochondrial DNA genome.
Of the enzymes, the major functions include oxidation of pyruvate and fatty acidsand the citric acid cycle. Mitochondria associated membranes MAM The mitochondria-associated ER membrane MAM is another structural element that is increasingly recognized for its critical role in cellular physiology and homeostasis.
Once considered a technical snag in cell fractionation techniques, the alleged ER vesicle contaminants that invariably appeared in the mitochondrial fraction have been re-identified as membranous structures derived from the MAM—the interface between mitochondria and the ER.
Not only has the MAM provided insight into the mechanistic basis underlying such physiological processes as intrinsic apoptosis and the propagation of calcium signaling, but it also favors a more refined view of the mitochondria. Though often seen as static, isolated 'powerhouses' hijacked for cellular metabolism through an ancient endosymbiotic event, the evolution of the MAM underscores the extent to which mitochondria have been integrated into overall cellular physiology, with intimate physical and functional coupling to the endomembrane system.
Phospholipid transfer The MAM is enriched in enzymes involved in lipid biosynthesis, such as phosphatidylserine synthase on the ER face and phosphatidylserine decarboxylase on the mitochondrial face.
In particular, the MAM appears to be an intermediate destination between the rough ER and the Golgi in the pathway that leads to very-low-density lipoproteinor VLDL, assembly and secretion. One of its components, for example, is also a constituent of the protein complex required for insertion of transmembrane beta-barrel proteins into the lipid bilayer.
Other proteins implicated in scaffolding likewise have functions independent of structural tethering at the MAM; for example, ER-resident and mitochondrial-resident mitofusins form heterocomplexes that regulate the number of inter-organelle contact sites, although mitofusins were first identified for their role in fission and fusion events between individual mitochondria.
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. Organization and distribution Typical mitochondrial network green in two human cells HeLa cells Mitochondria and related structures are found in all eukaryotes except one—the Oxymonad Monocercomonoides sp.
The population of all the mitochondria of a given cell constitutes the chondriome. A single mitochondrion is often found in unicellular organisms.
The association with the cytoskeleton determines mitochondrial shape, which can affect the function as well: However, the mitochondrion has many other functions in addition to the production of ATP.
Energy conversion A dominant role for the mitochondria is the production of ATPas reflected by the large number of proteins in the inner membrane for this task.
This is done by oxidizing the major products of glucose: When oxygen is limited, the glycolytic products will be metabolized by anaerobic fermentationa process that is independent of the mitochondria. ADP returns via the same route. Pyruvate and the citric acid cycle Main articles: Pyruvate dehydrogenasePyruvate carboxylaseand Citric acid cycle Pyruvate molecules produced by glycolysis are actively transported across the inner mitochondrial membrane, and into the matrix where they can either be oxidized and combined with coenzyme A to form CO2, acetyl-CoAand NADH or they can be carboxylated by pyruvate carboxylase to form oxaloacetate.
Adding more of any of these intermediates to the mitochondrion therefore means that the additional amount is retained within the cycle, increasing all the other intermediates as one is converted into the other. Hence, the addition of any one of them to the cycle has an anaplerotic effect, and its removal has a cataplerotic effect.
These anaplerotic and cataplerotic reactions will, during the course of the cycle, increase or decrease the amount of oxaloacetate available to combine with acetyl-CoA to form citric acid. This in turn increases or decreases the rate of ATP production by the mitochondrion, and thus the availability of ATP to the cell.
With each turn of the cycle one molecule of acetyl-CoA is consumed for every molecule of oxaloacetate present in the mitochondrial matrix, and is never regenerated.JSTOR is a digital library of academic journals, books, and primary sources. Yahoo Lifestyle is your source for style, beauty, and wellness, including health, inspiring stories, and the latest fashion trends.
During a heart attack, the supply of oxygen to heart cells is decreased. This reduced oxygen level, called hypoxia, causes the cell's powerhouses, the mitochondria, to fragment, impairing cell. Physical education activities.
Science laboratory activities. students learn about the structure and unique physical and chemical properties (specific heat, heat of fusion, capillary action, cooling and heating rates, universal solvent, conductivity, and pH) inherent to water.
Have students produce a photo essay, slide show, or poster. Beyond the Horizon: Chronoschisms and Historical Distance. HANS KELLNER.
History and Theory, Theme Issue 50 (December ), Historical distance presents more complex issues than simply evaluating the meaning of the temporal span between a point in the past and some moment present to an observer.
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