Which of the following is not a property of facilitated diffusion?
Facilitated diffusion encompasses carrier and channel mediated passive movement strictly down electrochemical gradient sharing discriminating features versus simple diffusion and active transport. Transport is obligately mediated by integral proteins with defined binding sites or selectivity filters conferring high specificity for instance GLUT1 preferring D-glucose over L-glucose tenfold and aquaporin excluding ions while passing water at billion per second via NPA motif. It is saturable because limited carriers or channels create Vmax plateau when all sites occupied enabling competitive inhibition by cytochalasin B or phloretin and Michaelis-Menten kinetics. However it requires no direct ATP hydrolysis or coupling to sodium or proton gradients; driving force is solute's own chemical potential difference distinguishing it from primary pumps and secondary symporters that accumulate against gradient. Once gradient abolished net flux ceases although exchange continues. Regulation occurs via gating phosphorylation altering open probability or vesicular trafficking such as insulin induced GLUT4 translocation and vasopressin induced aquaporin insertion but energy controls availability not transport step itself. Thus energy dependence is not property of facilitated diffusion rather it conserves energy while enhancing selectivity speed and regulation for polar nutrients unable to cross lipid rapidly and needing control.
Ref: Alberts et al., Molecular Biology of the Cell, 6th ed., Chapter 11: Properties of Facilitated Diffusion.