Answer:
See below
Step-by-step explanation:
Potassium channels have the ability to allow only potassium ions to pass through with a remarkable accuracy. This is achieved due to the presence of a selectivity filter. There are 8 molecules of water that surround this filter. If the K+ ion is to go through the filter, it will have to lose these molecules. The dimensions of this pore, as determined by its 3D structure, correspond only to the K+ ions and not Na+ ions which are smaller in size and thus, will not be able to pass through the filter.