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Active transport

1. A kind of transport wherein ions or molecules move against a concentration gradient, which means movement in the direction opposite that of diffusion – or – movement from an area of lower concentration to an area of higher concentration. Hence, this process will require expenditure of energy, and the assistance of a type of protein called a carrier protein. (

2. The movement of materials across cell membranes and epithelial layers against an electrochemical gradient, requiring the expenditure of metabolic energy. (

3. 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. (

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