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Active Transport


1. The movement of a substance across a cell membrane against its concentration gradient (from low to high concentration). In all cells, this is usually concerned with accumulating high concentrations of molecules that the cell needs, such as ions, glucose and amino acids. If the process uses chemical energy, such as from adenosine triphosphate (ATP), it is termed primary active transport. (

2. The movement of a chemical substance by the expenditure of energy against a gradient in concentration or in electrical potential across a plasma membrane. (

3. The movement of ions or molecules across a cellular membrane from a lower to a higher concentration, requiring the consumption of energy. (

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