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Diffusion vs. Transport. In biology, an ion transporter is a transmembrane protein that moves ions (or other small molecules) across a biological membrane to accomplish many different biological functions, including cellular communication, maintaining homeostasis, energy production, etc. [1] There are different types of transporters including pumps, uniporters, antiporters, and symporters.
(4) The transporter opens to the inside while both the potassium ions and the phosphorylated group leaves it. A transport protein (variously referred to as a transmembrane pump , transporter , escort protein , acid transport protein , cation transport protein , or anion transport protein ) is a protein that serves the function of moving other ...
The sodium-calcium exchanger (often denoted Na + /Ca 2+ exchanger, exchange protein, or NCX) is an antiporter membrane protein that removes calcium from cells. It uses the energy that is stored in the electrochemical gradient of sodium (Na +) by allowing Na + to flow down its gradient across the plasma membrane in exchange for the countertransport of calcium ions (Ca 2+).
Substances that are transported across the cell membrane by primary active transport include metal ions, such as Na +, K +, Mg 2+, and Ca 2+. These charged particles require ion pumps or ion channels to cross membranes and distribute through the body. Most of the enzymes that perform this type of transport are transmembrane ATPases.
Powered by ATP, the pump moves sodium and potassium ions in opposite directions, each against its concentration gradient. In a single cycle of the pump, three sodium ions are extruded from and two potassium ions are imported into the cell. Active transport is the movement of a substance across a membrane against its concentration gradient. This ...
Thermodynamically the flow of substances from one compartment to another can occur in the direction of a concentration or electrochemical gradient or against it. If the exchange of substances occurs in the direction of the gradient, that is, in the direction of decreasing potential, there is no requirement for an input of energy from outside the system; if, however, the transport is against ...
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The pore of sodium channels contains a selectivity filter made of negatively charged amino acid residues, which attract the positive Na + ion and keep out negatively charged ions such as chloride. The cations flow into a more constricted part of the pore that is 0.3 by 0.5 nm wide, which is just large enough to allow a single Na + ion with a ...