The alternative to active transport ... Hydrogen pumps build up an electrochemical gradient of H+ ions in cells to power cellular respiration. Transmembrane proteins are proteins that cross ...

"The channel-like protein binds potassium, at first very specifically and with high affinity, while the pump enables an active transport that can enrich potassium in the cell by 10,000-fold." ...

This takes place when molecules diffuse across the cell membrane by travelling through specific transport proteins ... concentration with energy: The proteins pump sodium out of the cells and ...