[kapital]

How can cells differ from the ions that has the same charge? For example, when cell is pushing up sodium, why goes sodium only and not potassium for example?
                                                                                                  thanx, by

[Wreath]

because the ions doesn't have the same size. it depends on hydratation of the ion, so although Na⁺ atom is smaller than K⁺, Na⁺ has bigger hydratation cover. So Na⁺ just doesn't fit in K⁺ ion channels. more, there are amino acid residues in every channel that are specific for recognizing only the size of ion that is typical for.
although this doesn't mean that K⁺ can't go through the Na⁺ channel. It can, but there's much lower affinity.

[xiaojunzhang]

That's great,thank you