Transmembrane ATPase: Difference between revisions
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#REDIRECT [[ATPase]] |
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'''Transmembrane ATPases''' are [[integral membrane protein]]s that use energy from the [[hydrolysis]] of [[adenosine triphosphate]] (ATP) to transport [[ion]]s and other solutes between the solutions on either side of a [[biological membrane]] and against a solute's natural direction of flow. |
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Transmembrane ATPases import many of the metabolites necessary for [[cell (biology)|cell]] [[metabolism]] and export toxins, wastes, and solutes that can hinder cellular processes. An important example is the sodium-potassium exchanger (or [[NaKATPase|Na<sup>+</sup>/K<sup>+</sup>ATPase]]), which establishes the ionic concentration balance that maintains the [[cell potential]]. |
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Besides exchangers, other categories of transmembrane ATPase include cotransporters and pumps (however, some exchangers are also pumps). Some of these, like the Na<sup>+</sup>/K<sup>+</sup>ATPase, cause a net flow of charge, but others do not. These are called "electrogenic" and "nonelectrogenic" transporters, respectively. |
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The coupling between ATP hydrolysis and transport is more or less a strict chemical reaction, in which a fixed number of solute molecules are transported for each ATP molecule that is hydrolyzed; for example, 3 Na<sup>+</sup> ions inward and 2 K<sup>+</sup> ions outward per ATP hydrolyzed, for the Na<sup>+</sup>/K<sup>+</sup> exchanger. |
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Transmembrane ATPases harness the chemical potential energy of ATP, because they perform [[work]]: they transport solutes in a direction opposite to their [[thermodynamic|thermodynamically]] preferred direction of movement—that is, from the side of the membrane where they are in low concentration to the side where they are in high concentration. This process is considered [[active transport]]. |
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==ATP synthetase== |
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The ATP synthetase (or [[ATP synthase]]) of [[mitochondria]] and [[chloroplast]]s is an [[anabolic]] enzyme that harnesses the energy of a transmembrane [[proton]] gradient as an energy source for adding an [[inorganic phosphate]] group to a molecule of [[adenosine diphosphate]] (ADP) to form a molecule of adenosine triphosphate (ATP). ATP synthetase can also function in reverse; that is, use energy released by ATP hydrolysis to pump protons against their thermodynamic gradient. |
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For more detailed information take a look at [http://www.biologie.uni-osnabrueck.de/biophysik/Feniouk/Home.html "ATP synthase - a splendid molecular machine"] |
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See also: |
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* [[Na-K pump]] |
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* [[ATP synthase]] |
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Latest revision as of 05:13, 29 August 2004
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