How Does the Potassium Channel Maintain Selectivity for Potassium Versus

Multiple Choice

How does the potassium channel maintain selectivity for potassium versus sodium ions?

A) The ion size is the determining factor.
B) The size of the ion and associated waters relative to the pore size are the determining factors in channel selectivity.
C) Dehydration of the potassium ion is compensated energetically by interactions with oxygen atoms in the selectivity filter, which is not possible with sodium ions.
D) Potassium ions associate with six molecules of water while sodium associates with four, thus allowing selectivity.
E) None of the answers is correct.