sodium potassium pump

[Evil]

Why do cells tend to mantain low internal concentrations of Na ions and high internal concentration of k ions despite the surrounding fluid being low in k ions but high in na ions?

[Jikx]

what a coincidence.. I just about this 30minutes ago for exam revision!

Seems it is necessary in the transport of glucose across the intestinal epithelium.

Glucose+Na (symport) into the epithelial cell.
3.Na expelled into the blood stream, while 2K taken. (uses ATP)
Glucose then diffuses out of the cell into blood.

At least i hope thats right.. cause then we'll both be in trouble.


Also necessary in nerve function i believe, pumping out 3Na while taking in 2K means a net charge of -1 within the cell, returning the negative electrical differences across the membrane after an action potential (where the membrane depolarises).

There's probably thousands of things link to this.

[Njorl]

what a coincidence.. I just about this 30minutes ago for exam revision!

Seems it is necessary in the transport of glucose across the intestinal epithelium.

Glucose+Na (symport) into the epithelial cell.
3.Na expelled into the blood stream, while 2K taken. (uses ATP)
Glucose then diffuses out of the cell into blood.

At least i hope thats right.. cause then we'll both be in trouble.


Also necessary in nerve function i believe, pumping out 3Na while taking in 2K means a net charge of -1 within the cell, returning the negative electrical differences across the membrane after an action potential (where the membrane depolarises).

There's probably thousands of things link to this.

That indicates the purpose, but what is the cause?

Njorl

[Jikx]

The cause.. is the sodium/potassium ATPase ion pump? lol

[Monique]

The sodium potassium pump is required to maintain osmotic balance and stabilize the cells volume. If you treat an animal cell with ouabain, which inhibits the Na+/K+ pump, it will swell and often burst.

Cells contain mostly negatively charged organic molecules, so they require cations for a counter charge balance: K+. This will create a large osmotic gradients, that would pull water into the cell, so it will pump out Na+.

The pump is also able to generate membrane potential in nerve cells because of its electrogenic effect, but 90% of the membrane potential depends indirectly on the Na+/K+ pump.

[Evil]

i suppose the next question would be why cells contain mostly negatively charged organic molecules?

[Jikx]

http://www.bio.psu.edu/courses/fall2003/biol141_901/membrane_potential/electrophysiology.html

Apparently because of AminoAcids.. maybe DNA too?

http://64.233.167.104/search?q=cache:sCL2TvoIPEsJ:www.csus.edu/indiv/n/nguyenh/Answers%2520to%2520Exams/Bio180%2520Fall2003/24Sep2003%2520Biol180%2520Exam1.htm+mostly+negativ ely+charged+molecules+in+the+cell&hl=en


*sigh* if only google was allowed during tests :)