Active permeability can be classified into two main types:
Primary Active Transport: In this type, the energy for transport is directly derived from ATP hydrolysis. A classic example is the sodium-potassium pump (Na+/K+ ATPase), which maintains the electrochemical gradient across the cell membrane by pumping sodium out and potassium into the cell. Secondary Active Transport: Here, the energy is derived indirectly from the electrochemical gradient created by primary active transport. This can be further divided into symport and antiport mechanisms. In symport, both substances move in the same direction, while in antiport, they move in opposite directions.
