secondary active transport

Secondary active transport is a cellular process where molecules are moved across a membrane using energy from an existing gradient of another substance, typically established by primary active transport. Instead of directly using ATP (energy), it relies on the electrochemical gradient created by the active transport of one substance, such as sodium ions, to drive the movement of another molecule in the same direction (co-transport) or opposite direction (counter-transport). This process allows cells to efficiently uptake or remove molecules without directly consuming energy each time, leveraging stored energy in the form of ion gradients.