Simple Question RE: NA-K Pump

Hans-Georg Klieber klieber at papin.HRZ.Uni-Marburg.DE
Sat Oct 14 04:00:12 EST 1995

Lynette (lynette2 at wrote:
> Is there a "sodium-potassium pump" in any other type of animal cell 
> besides the nerve cells?  If so, what does it do, briefly?

All living cells (plant and animal) have a primary active 
ion transport system to establish and maintain certain
ion gradients and a membrane potential.

A "primary active ion transport" (=a pump) is fueled
by ATP hydrolysis which delivers the energy which is
necessary to build up electrochemical gradients at
the membrane.

In plants the standard primary active ion transport in
the cell membrane is a H-ATPase (=proton pump) in animal
cells it is the Na-K-ATPase (=sodium-potassium-pump).

The need for the ion pump may be more obvious
in a nerve cell because because it dissipates ion gradients
during action potentials. But any living living cell
must transport a lot of substances across the cell membrane
to maintain its metabolism. In order to have control over
the direction and intensity of those transports they
must be energized (as opposed to be purely dissipative).

To accopmplish this the ion gradients and the membrane
potential which are maintained by the _primary active_
pump are utilized by _secondary_ active transport systems.
(eg: the transport of an amino acid into the cell may
be fueled by the electrochemical gradient of sodium).
They are "secondary active" because they can build up
an electrochemical gradient for a substrate (which the 
cell may want to accumulate in the cytoplasm) but only
at the expense of dissipating the electrochmical gradient
of a second substrate (usually Na).

Live depends on the permanent exchange of energy and
matter between the cell and its environment. In a wider
perspective the ion pump (even bacteria have some sort 
of them) can be understood as the 
molecular machinery by which the living organism directs
the flow of energy and matter and tries to counteract
the entropy. 

Dr. Hans-Georg Klieber
Institute for Physiology, University of Marburg
Deutschhausstrasse 2, 35033 Marburg, Germany
Office: +49-6421-282290, Home: +49-6421-25680

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