Re: TOJC: Crown Ethers

thompsdp@plu.edu
Wed, 04 Dec 1996 07:53:48 -0800 (PST)

Even though the book might make it sound like a diffusion process, the
Na/K ATPase pump is indeed active because it can transport against a
concentration gradient. I think your confusion might be in the fact that
K+ is the second half of the process, and follows the removal of Na+ in a
3:2 ratio (3 Na+ removed from the cell, 2 K+ brought it), which is a very
active process. This mechanism is what is responsible for the
overall negative charge inside a cell. Just keep in mind that both ions
are transported by this mechanism, and K+ is second.

Hope that helps,
thompsdp

On Tue, 3 Dec 1996 uhlerdd@plu.edu wrote:

> Good Evening Chem Kids,
> I was reading section 10.22B and it discusses some crown ethers
> responsible for Na and K concentrations across cell membranes. It
> describes the Na/K pump as a mechanism where by certain crown ethers
> (nonactin) associate more readily with K and the internal structure of the
> cell (hydrophobic lipid ends) allows permeability of K ions when
> associated with a transport ether. I realize it is an active mechanism by
> the cell, but doesn't it still mainly rely on diffusion rates rather than
> a more active form of "pumping". I don't know, but it seems a poor
> analogy to describe it as pumping when it is more of an ion association to
> PERMIT permeability of an ion rather than necessitate its movement.
>
> Curiously,
> Dave
>
>