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Encyclopedia: Concentration gradient (240 words) |
 | A concentration gradient is the difference in density of a substance over a distance. |
| One of these species is allowed to flow from high to low concentration, which yields the entropic energy to drive the transport of the other solute from a low concentration region to a high one. |
| Active transport typically moves molecules from low concentration to high, or against their concentration gradient, an process that would be entropically unfavorable were it not stoichiometrically coupled with the hydrolysis of ATP. |
| Concentration gradient - definition of Concentration gradient in Encyclopedia (393 words) |
| Some archaea, most notably halobacteria, make proton gradients by pumping in protons from the environment with the help of the solar driven enzyme bacteriorhodopsin, here it is used for driving the molecular motor enzyme ATP synthase to make the necessary conformational changes required to synthesize ATP. |
| Proton gradients are also be made by bacteria by running ATP synthase in reverse, this is used to drive flagellas. |
| Large enough quantities of ATP cause it to create a transmembrane proton gradient, this is used by fermenting bacteria which do not have an electron transport chain, and hydrolyze ATP to make a proton gradient, which they use for flagella and transport of nutrients into the cell. |
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