In the veins of a plant, proton pumps work hard moving hydrogen ions out of the plant cells. This process generates proton concentration gradients, which are high amounts of hydrogen outside the cell membrane. These gradients represent potential energy that can be used by cell transporters to bring nutrients in and out of a cell. Let's take a closer look at a plant cell. As you can see, the two pumps are moving hydrogen from inside the plant cell, through the membrane, to the outside of the cell called the appleplast. The bottom pump called ATPase is using a high energy molecule called ATP, which makes it stronger in moving hydrogen. The top pump, called pyrophosphatase, uses a lower energy molecule called pyrophosphate or PPI to move protons out. As the protons build up in the appleplast, the gradient shifts and causes the weaker pump to reverse, since it cannot move protons against the gradient. The energy from moving the protons in this direction is used to create PPI. Sugar moves through plants in a variety of ways. By understanding these processes, researchers may find new ways to alter plants so that they'll grow more roots, shoots, and leaves.