Ion pump (physics)
An ion pump (also referred to as a sputter ion pump) is a type of vacuum pump capable of reaching pressures as low as 10−11 mbar under ideal conditions. An ion pump ionizes gas within the vessel it is attached to and employs a strong electrical potential, typically 3–7 kV, which allows the ions to accelerate into and be captured by a solid electrode and its residue.
Penning trap
The basic element of the common ion pump is a Penning trap. A swirling cloud of electrons produced by an electric discharge is temporarily stored in the anode region of a Penning trap. These electrons ionize incoming gas atoms and molecules. The resultant swirling ions are accelerated to strike a chemically active cathode (usually titanium). On impact the accelerated ions will either become buried within the cathode or sputter cathode material onto the walls of the pump. The freshly sputtered chemically active cathode material acts as a getter that then evacuates the gas by both chemisorption and physisorption resulting in a net pumping action. Inert and lighter gases, such as He and H2 tend not to sputter and are absorbed by physisorption. Some fraction of the energetic gas ions (including gas that is not chemically active with the cathode material) can strike the cathode and acquire an electron from the surface, neutralizing it as it rebounds. These rebounding energetic neutrals are buried in exposed pump surfaces.
Ion transporter
In biology, an ion transporter, also called an ion pump, is a transmembrane protein that moves ions across a plasma membrane against their concentration gradient, in contrast to ion channels, where ions go through passive transport. These primary transporters are enzymes that convert energy from various sources, including ATP, sunlight, and other redox reactions, to potential energy stored in an electrochemical gradient. This energy is then used by secondary transporters, including ion carriers and ion channels, to drive vital cellular processes, such as ATP synthesis.
Energy source
Such ion pumps can use energy from a variety of sources, including ATP or the concentration gradient of another ion (sometimes called an "ion exchanger"). Symporters transport anions down their concentration gradient to fuel the transport of another type of ion in the same direction, while antiporters also use the concentration gradient in this same manner but transport in the opposite direction. In contrast, uniporters transport a single ion down its concentration gradient. In all of these cases, there is at least one driving ion that travels down its concentration gradient, thereby providing the energy of the system. Ions that are moved up their concentration gradients are called the driven ion. For a more detailed description of one particular kind of ion pump, see Na+/K+-ATPase.
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