Michael Clarkson explains.
That’s not an ion channel, that’s sodium/potassium ATPase, also known as the sodium potassium pump. Ion channels are selective (or nor so selective) conduits through the plasma membrane that allow ions to flow down the concentration gradient. The Na/K pump uses ATP as a source of energy to pump Na and K ions against the concentration gradient.
That is correct. It is the Na/K ATPase/pump, which is a specialized ion channel.
From the linked post (my emphasis):
cells frequently need to move charged atoms (ions) across the membrane. This job is primarily performed by two kinds of protiens: channels that create specialized tunnels through the membrane, and transporters that mechanically transfer ions across the membrane. These are distinct activities, usually carried out by different families of proteins.
The fact that (as discussed in the post) one protein family includes both transporters and channels does not mean that all transporters are “specialized ion channels.” Especially since Na/K ATPase is not a member of this particular family, I think that Will is correct that your post-title is misleading at best. (I’m being nice; I think it’s simply wrong.)
You are probably right. This may have to do with the language in which I learned this – Serbo-Croatian – in which everything is a channel is it allows or helps stuff to cross the membrane. Then there was a complex classification of channels, starting with simple pores (e.g., in the capillary endothelium, including in the glomerulus of the kidney, the aldosterone-regulated pores in the collecting ducts of the kidney, etc.), then various kinds of channels, including ion channels, which require some kind of trigger (electrical, mechanical, hormone….) to open or close, and finally energy-dependent transporters like this one. So this may have to do with the difference in terminology or textbook organization in different languages/countries, or, you may be correct.
Anyway, this post is a link to Michael, and the videos are just some cool illustrations I quickly added for fun.
Obviously it’s not a big deal. I prefer to use scientific terminology to keep things distinct rather than to emphasize similarities–to split, not to lump. I had a colleague who insisted on teaching active-transport pumps as a type of enzymes, and that really made me crazy.
Thanks for the link, Bora; only just noticed it. I should check my incoming traffic sources more often, huh?
As to the distinction between ion channels and transporters, the primary distinction between them is electrochemical dependence and (operationally) rate of transport. A thermodynamic difference probably doesn’t sound like a big deal, but in practice it amounts to a significant structural difference, except (as in this case) when it doesn’t. That’s biology for you.
New comments have been temporarily disabled. Please check back soon.
Earlier this morning, I have moved my blog over to the Scientific American site – http://blogs.scientificamerican.com/a-blog-around-the-clock/.…
This blog can now be found at http://blog.coturnix.org and the feed is http://blog.coturnix.org/feed/. Please adjust your…
It is with great regret that I am writing this. Scienceblogs.com has been a big part…
The list is growing fast – check the submissions to date and get inspired to submit…
At bottom every man know well enough that he is a unique being, only once on…