1 Allows diffusion of large, membrane insoluble compounds such as sugars (glucose) and amino acids. 2  Does not require energy (passive transport). 3  Substance binds to membrane transport protein. 4  Molecules may enter the cell and leave the cell through the transport protein.ctive Transport. 1  Movement across membrane with an energy cost because if moves the molecule against a concentration gradient. 2  Used to pump specific compounds in or out of the cell. 3  Requires energy to overcome the concentration gradient. 4  Requires specific membrane transport proteins.