Voltage-sensitive K+ channels are 1,000 times more permeable to K+ than to Na+ because
a. K+ ions are smaller than Na+ ions.
b. K+ ions have a lower charge density than Na+ ions.
c. a selectivity filter removes the water molecules from K+ ions but not from Na+ ions.
d. K+ ions are more concentrated inside the cell than outside the cell.
Ans: c. a selectivity filter removes the water molecules from K+ ions but not from Na+ ions.
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