[dielske]

Dear all,

I wonder why K⁺ is so important for bacerial cells to keep their pH at a normal level.

I do not see why K⁺ would change the pH since K⁺ will not react with free H⁺?

Any ideas?

thanks

[rjb]

Dielske,

The K+ ions play a pretty important part in maintenance of intracellular pH, but its not really just about the chemistry of the K+ ion as such. From what I remember (it was a while ago!), intracellular concentration of K+ is greater within the cell than the outside, but the concentration of Na+ and Cl- is lower. This sets up a ionic gradient accross the cell membrane, the intracellular surface bearing a net negative charge, which powers the influx of H+ ions and hence can be used to  regulate intracellular pH. H+  ions are allowed into the cell via ion channels, which I think can undergo conformation change and regulate H+ influx.

Hope this helps a bit

R

[dielske]

hallo rjb,

Ok I can see this.
But what if the pH in the cell is lowering (getting too low) then how van K⁺ play a role?

It was more in this context I asked the question.


And to see if I understand you: you do mean that the charge inside is lower since there are more Na⁺ outside then K⁺ inside (combined with a lot of H⁺ outside). Or not?

[Wreath]

this might help you.
http://onlinelibrary.wiley.com/doi/10.1111/j.1432-1033.1988.tb14055.x/abstract

[dielske]

this might help you.
http://onlinelibrary.wiley.com/doi/10.1111/j.1432-1033.1988.tb14055.x/abstract

Its a start, but its about eukaryotic cells.. but it might help.

[rjb]

Dielske,

As the extracellular pH drops, the cells begins active transport of H+ out of the cell, probably using K+/H+ antiports. This is where the K+ comes into the equation. By taking up 1 K+ ion for every proton expelled, overall ionic balance is maintained whilst increasing intracellular pH.

Regarding charge, you've got the right idea. I can't remember offhand how this all works in prokaryotes, but in eukaryotes, Na+/K+ ports remove Na+ from the cell and actively transport K+ into the cell in a 3:2 ratio, giving rise to the membrane potential discussed in the previous reply. Its actually quite a complex process, so it might be worth having a look at Molecular Cell Biology (Lodish) or doing a web search for membrane potential or similar.

Kind Regards

R

[Wreath]

http://www.ncbi.nlm.nih.gov/books/NBK21687/#A4106

well, the problem here is that lodish is about eukaryotic cells..

[dielske]

Dielske,

As the extracellular pH drops, the cells begins active transport of H+ out of the cell, probably using K+/H+ antiports. This is where the K+ comes into the equation. By taking up 1 K+ ion for every proton expelled, overall ionic balance is maintained whilst increasing intracellular pH.

Regarding charge, you've got the right idea. I can't remember offhand how this all works in prokaryotes, but in eukaryotes, Na+/K+ ports remove Na+ from the cell and actively transport K+ into the cell in a 3:2 ratio, giving rise to the membrane potential discussed in the previous reply. Its actually quite a complex process, so it might be worth having a look at Molecular Cell Biology (Lodish) or doing a web search for membrane potential or similar.

Kind Regards
R

Yes, I remember about the K and Na exchange in eukaryotes, but wasnt sure this is also the case in prokaryotes.

I remember that the K/Na exchange is very important for the depolarisation of  cells in order to pass neural messages.. But the link with the pH system seems a bit strange.

I guess that what you are saying is indeed a reason or explenation why K⁺ (might) is important.

[dielske]

K+ ions play a central role in generating action potentials and rhythmic patterns, as well as in dendritic signal processing in neurons

What do you mean with rhythmic patterns?

And dendritic signal processing? ok, but thats in eurkaryotes.