# Potassium Channel ion rate and Gradient

Gold Member

## Main Question or Discussion Point

Hi All,
A potassium channel is designed to filter out potassium ions at a maximum rate of 100,000,000 ions s-1
A common concentration (cell's interior) of potassium is 100 mM and 5 mM outside.
This means there is 553 water molecules for 1 potassium ion inside (55.3/0.100) and 11,060 water molecules for a ion outside (55.3/0.005).

If the channel acts as a sieve then what happen to the local concentrations, inside and outside?

ref:
rate =>
http://www.pdb.org/pdb/static.do?p=education_discussion/molecule_of_the_month/pdb38_1.html
water =>
http://www.pdb.org/pdb/static.do?p=education_discussion/molecule_of_the_month/pdb38_4.html

ps: local concentration (concentration that exists just around the channel ~ few nm)