Please explain why cells pump H+ out to bring in sugar. Solution A proton pumping ATPases is specific to plants, fungi and some protists and aids in transmembrane movement of substances. The H+-ATPase present in the plasma membrane in plants and fungi couple ATP hydrolysis with proton transport creating a pH and potential difference across plasma membrane which is essential for secondary transporters which transport minerals, sugars, and amino acids. H+ ATPases create a proton gradient, where ATP hydrolysis couples with H+ transport outside the cells causing the secondary transporters to allow sugars to enter the cells. Once, the uptake is finished, the ATPase activity is stopped and the H+ gradient is normalized..