There are various similarities between primary and secondary active transport. One similarity is that both types of transport are forms of active transport. Both types are also involved in the pumping of molecules against the concentration gradient, from a low concentration to high concentration. They both also share the common purpose of increasing the speed of movement of molecules across the cell membrane. Additionally, transmembrane proteins are specific to molecules transported across the membrane. These transmembrane proteins are involved in facilitating primary and secondary active transport.