Three sodium ions inside the office float near the pump. The pump recognizes them and binds to them tightly, like a claw machine grabbing a prize.
"Get in," The Pump rumbled.
"Active Transport," The Pump said, its voice echoing through the membrane. "We don't wait for the world to give us what we need. We pay the price and we take it." active transport via a protein channel
Instead of using ATP directly, this method uses the energy stored in an electrochemical gradient previously created by primary active transport. As one ion moves down its concentration gradient, it provides the energy for another molecule to move up its own gradient through the same protein. Key Examples of Protein Pumps Three sodium ions inside the office float near the pump