The transport of a certain molecule exhibits the following characteristics: (1) The molocule moves down its concentration gradient; (2) at concentrations above a given level, the rate of transport does not increase; and (3) cellular energy is not required for transport to occur. WHich transport process is at work?
This process is facilitated diffusion, which requires a carrier molecule but not cellular energy. THe energy for this process is provided by the concentration gradient of the substance being transported. WHen all the carriers are actively involved in transport, the rate of transport reaches a saturation point.