English: This picture represents antiport. The yellow triangle shows the concentration gradient for the yellow circles while the blue triangle shows the concentration gradient for the blue circles and the purple rods are the transport protein bundle. The blue circles are moving against their concentration gradient through a transport protein which requires energy while the yellow circles move down their concentration gradient which releases energy. The yellow circles produce more energy through chemiosmosis than what is required to move the blue circles so the movement is coupled and some energy is cancelled out. One example is the sodium-proton exchanger which allows protons to go down their concentration gradient into the cell while pumping sodium out of the cell.