Do you mean ion pumps in the membrane of cell?
If so, then ion pumps maintain an electrochemical gradient across the membrane.
Membrane proteins can serve a variety of key functions:
Junctions – Serve to connect and join two cells together.
Enzymes – Fixing to membranes localises metabolic pathways.
Transport – Responsible for facilitated diffusion and active transport.
Recognition – May function as markers for cellular identification.