Active transport by protein pumps

Notice that the particles to be transported are moved from a lower concentration to a higher particle

concentration. This involves the movement of the pump protein. This requires energy produced in

the form of ATP from cell respiration

An important example of this is the movement of sodium and potassium ions across the membranes of nerve cells to send electrical impulses along a nerve.

Figure 1. 4.5 http://en.wikipedia.org/wiki/Image:Scheme_sodium-potassium_pump-en.svg