Uniporrers and ion channels support facilitated diffusion across biomembranes. Although both are examples of facilitated diffusion, the

Question:

Uniporrers and ion channels support facilitated diffusion across biomembranes. Although both are examples of facilitated diffusion, the rates of ion movement via an ion channel are roughly 10⁴- to 10⁵ -fold faster than that of molecule movement via a uniporter. What key mechanistic difference results in this large difference in transport rate? What contribution to free energy (∆G) determines the direction of transport?