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
Active transport is a type of cellular transport. In contrast to passive transport, the active transport involves the movement of a substance (e.g. ions, glucose, and amino acids) across a membrane from a region of its lower concentration to a region of its higher concentration against a concentration gradient. Since it is against the concentration gradient, this type of transport uses cellular energy (e.g. ATP) (in contrast to passive transport that utilizes kinetic and natural energy). The cellular energy is supplied through cell respiration. Mitochondria are the cell organelles in the cytoplasm that provide such type of energy source and also regulate energy release. Respiratory poisons block energy release, so they can prevent active transport. The common sites of active transport are root hair cells the wall of small intestine (villi).
Active transport may be primary or secondary. A primary active transport is one that uses chemical energy in the form of ATP whereas a secondary active transport uses an electrochemical gradient.