what characteristics of ions are ion channels selective for

what characteristics of ions are ion channels selective for? In addition to being selective for different ions, what are the different waysthat ion channels can be gated?

Solution

What characteristics of ions are ion channels selective for?

Ions can\'t cross the membrane by simple diffusion. Thus, there are ion channels for their movement across the cell membrane. The channels are selective for specific ions. This is ensured by the size of the opening. Each channel has an open path which spans the membrane. Inside this open path, there are water molecules which act as a screening barrier or an aquaeous channel. Only those ions can pass through this barrier, whose size is smaller than this barrier. Thus we can say, that the ion channels are selective for the size of the ions passing through them.

What are the different ways that ion channels can be gated?

There are three basic mechanisms for gating ion channels, these are as follows:

1. Ligand-gated ion channel : In this type, a ligand [which can be a hormone or neurotransmitter] binds to the receptor on the channel and induces change in the ion channel. This leads to opening of the channel and movement of ions takes place. The ligand binds on the extra-cellular site of the cell.

2. Voltage gated ion channel : We see these kinds of ion channels on nerve and muscle cell, where passage of nerve impulse is due of opening and closing of Na+ channels. This opening and closing is induced by change in membrane potential, thus named as \"Voltage gated\".

2. Phosphorylation based ion channel : Under this category, one of the most commonly studied example is Na+/ K+ ATP. The opening of such channels is induced after the phosphorylation of the channel from inside of the cell, with the help of ATP.