What is the design of carrier protein molecules?
The two different kinds of special transport proteins in cell membranes have been called carriers and channels based on how they likely work to transport molecules. Carrier proteins never form a direct connection between the inside and the outside of the cell. A good analogy for understanding the basic design behind carrier proteins is that they are like the Panama Canal. The Panama Canal has a gate on the Atlantic side and one on the Pacific side and a separate canal in between (in which the water level and ship can be raised or lowered). Thus, a ship crossing the canal from east to west enters through the gate on the Atlantic side and the gate closes. While the ship is traversing the canal from east to west (with both gates closed), the water level is adjusted by pumping water in or out of the canal. When the ship reaches the west end of the canal, the water level is now the same as the Pacific Ocean. The gate to the Pacific side opens and the ship leaves the canal. At no time during
