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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.
A membrane transport protein is a membrane protein involved in the movement of ions, small molecules, and macromolecules, such as another protein, across a biological membrane. Transport proteins are integral transmembrane proteins ; that is they exist permanently within and span the membrane across which they transport substances.
The rate of ion transport through the channel is very high (often 10 6 ions per second or greater). Ions pass through channels down their electrochemical gradient, which is a function of ion concentration and membrane potential, "downhill", without the input (or help) of metabolic energy (e.g. ATP, co-transport mechanisms, or active transport ...
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 materials within an organism. Transport proteins are vital to the growth and life of all living things.
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.
Members of the Organic Anion Transporter (OAT) Family (organic-anion-transporting polypeptides, OATP) are membrane transport proteins or 'transporters' that mediate the transport of mainly organic anions across the cell membrane. Therefore, OATPs are present in the lipid bilayer of the cell membrane, acting as the cell's gatekeepers.
The discovery of the existence of this type of transporter protein came from the study of the kinetics of cross-membrane molecule transport. For certain solutes it was noted that the transport velocity reached a plateau at a particular concentration above which there was no significant increase in uptake rate, indicating a log curve type response.
Pendrin is an anion exchange protein that in humans is encoded by the SLC26A4 gene (solute carrier family 26, member 4). [5] [6] Pendrin was initially identified as a sodium-independent chloride-iodide exchanger [7] with subsequent studies showing that it also accepts formate and bicarbonate as substrates.