Potassium Channel ion rate and Gradient

[somasimple]

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).

Ionic concentration / number of ions

 

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)

[Getting A Life]

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

 

The K/Na channel is ATP assisted, so can work against a gradient. 3 Na+ ions are expelled as 2 K+ ions are imported. The protein channel is not a sieve, it regulates the flow of ions according to cellular/extracellular conditions.

[somasimple]

Sorry but we are not speaking about NaK pump. I'm speaking about a simple K channel.

[Getting A Life]

Sorry mate, was in a hurry and didn't read properly, love the links by the way.

 

If the channel is a sieve the gradient must be higher (before sieving) and lower (in destination). Otherwise, it must be facilitated transport to work against a gradient.

 

Feedback regulation is huge in cellular metabolism. Levels will be monitored and adjusted, no idea how but typically involves an allosteric protein in the pathway.

[somasimple]

If the channel is a sieve the gradient must be higher (before sieving) and lower (in destination). Otherwise, it must be facilitated transport to work against a gradient.

Accordingly to the second link I provided and the actual cited gradients, the concentration is ever higher in the pore/channel than elsewhere then the gradient is lower (before sieving) and lower at destination. It does not work!

Otherwise and also in facilitated transport, you're facing the same situation... :naughty:

[Getting A Life]

Ahh, the plot thickens (and confounds a bit).

 

Perhaps the channel is coupled with another cellular metabolic event. I forget the name but one activity eg: bond cleaving, produces the energy to drive another. Much of cellular work is done in this manner. Balance and efficiency.

 

In a similar vein, as the other protein (Na+/K+ pump with facilitated transport) exports 3 Na+ and only imports 2 K+ this would imply an electrochemical gradient is created that might be utilised by other processes like the channel proteins you are examining.

 

Just theorising, hoping some edyarkated type will step in and reveal all. This stuff fascinates me, but is also hard for me to grasp.

 

Love will conquer :phones:

[somasimple]

In a similar vein, as the other protein (Na+/K+ pump with facilitated transport) exports 3 Na+ and only imports 2 K+ this would imply an electrochemical gradient is created that might be utilised by other processes like the channel proteins you are examining.

The electrochemical gradient can't work because the ions in the channel creates an electrostatic/electric force that is ever superior to an hypothetic electrochemical gradient.

[Getting A Life]

It is the coupling of exergonic reactions to endergonic that makes a cell's metabolism so efficient.