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It uses the large gradient of organic phosphate to move folate into the cell against its concentration gradient. The RFC protein can transport folates, reduced folates, the derivatives of reduced folate, and the drug methotrexate. The transporter is encoded by the SLC19A1 gene and is ubiquitously expressed in human cells.
In addition to a gradient of the nucleotide bound state of Ran, there is a gradient of the protein itself, with a higher concentration of Ran in the nucleus than in the cytoplasm. Cytoplasmic RanGDP is imported into the nucleus by the small protein NUTF2 (Nuclear Transport Factor 2), where RCC1 can then catalyze exchange of GDP for GTP on Ran.
The yellow triangle shows the concentration gradient for the yellow circles and the purple rods are the transport protein bundle. Since they move down their concentration gradient through a transport protein, they can release energy as a result of chemiosmosis. One example is GLUT1 which moves glucose down its concentration gradient into the cell.
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.
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 ...
An ion gradient has potential energy and can be used to power chemical reactions when the ions pass through a channel (red). Hydrogen ions, or protons, will diffuse from a region of high proton concentration to a region of lower proton concentration, and an electrochemical concentration gradient of protons across a membrane can be harnessed to ...
The concentration gradient set up by glucose concentrations fuels the process without the need for ATP. [18] When glucose binds to the glucose transporter, the protein channels change shape and undergo a conformational change to transport the glucose across the membrane. Once the glucose unbinds, the protein returns to its original shape.
The aromatic/arginine or "ar/R" selectivity filter is a cluster of amino acids that help bind to water molecules and exclude other molecules that may try to enter the pore. It is the mechanism by which the aquaporin is able to selectively bind water molecules and so to allow them through, and to prevent other molecules from entering.