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Animation: Active Transport

by Pearson
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Sometimes, a cell needs to move a solute against its concentration gradient. This process is called active transport, and it requires input of energy from ATP. For instance, most animal cells need to expel sodium ions (Na+) and take in potassium ions (K+), both against their concentration gradients. Here is how the sodium-potassium pump works. Sodium ions bind to a transport protein. ATP transfers a phosphate group to the protein, providing the energy that causes the protein to change shape and move the sodium ions across the membrane, where they are released outside the cell. Potassium ions now bind to the transport protein and the phosphate group is released. This causes the protein to return to its original shape, releasing the potassium ions inside the cell. The transport protein is now ready to repeat the process.
Sometimes, a cell needs to move a solute against its concentration gradient. This process is called active transport, and it requires input of energy from ATP. For instance, most animal cells need to expel sodium ions (Na+) and take in potassium ions (K+), both against their concentration gradients. Here is how the sodium-potassium pump works. Sodium ions bind to a transport protein. ATP transfers a phosphate group to the protein, providing the energy that causes the protein to change shape and move the sodium ions across the membrane, where they are released outside the cell. Potassium ions now bind to the transport protein and the phosphate group is released. This causes the protein to return to its original shape, releasing the potassium ions inside the cell. The transport protein is now ready to repeat the process.