What is the mechanism of carrier proteins?

Carrier proteins are a type of transmembrane protein involved in facilitated transport. They transport substances across the cell membrane by binding to ions or molecules on one side of the membrane and then changing their conformation in order to release the target ion or molecule on the other side. 

Carrier proteins transport ions and molecules across the cell membrane against the concentration gradient of the transporting molecule or when the phospholipid bilayer of the membrane is impermeable to a chemical. This type of active transport requires cellular energy. The rate of the transportation by carrier proteins is considerably lower than that of channel proteins.