Na/K pump

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pedro21101
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Na/K pump

Post by pedro21101 » Sat Aug 20, 2005 7:03 am

Does unicellular organisms living in fresh water have this pump? Maybe odd question but i need to know for sure how it is. I know that it is good in osmoregulation so that Na is exppelling out of cell with one water molecule. There i dont understant if main purpose is to low concetration of water in cell or increase concentration of Na ions in environment around cell. Fresh water is hypotonic solution, isnt it?

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Poison
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Post by Poison » Sat Aug 20, 2005 5:40 pm

As much as I know, Na+/K+ pump is present in neurons. Fish that lives in fresh water, actively transports excess water. I don't think it is somethng done with Na+/K+ pump.
Please someone correct me if I'm wrong. :)
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MrMistery
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Post by MrMistery » Sat Aug 20, 2005 7:02 pm

You're wrong. :D :D :D :D :D
Just about every eukaryotic cell you can name has a Na/K pump. i am not sure about prokaryotic cells but my guess is they have it too. It's just that it's function is much more vital in the neuron so many people have the wrong opinion that you can only find it there. 70% of the energy used by neuron is used by Na/K pump. But in any normal cell the quantity of energy used by this pump is up to 30%, because it is used to "finance" secondary active transport systems.
Now, i do not think if the pump has a role in osmoreglation since it does not expell water out of the cell. the pump has 3 spots for Na, 1 for the ATP, and 2 for K. When it is activated it gets 3 Na ions out of the cell and gets 2 K ions inside the cell, at the cost of 1 ATP. The main role is to expell na outside of the cell, because it is later used in antiports and simports-secondary active transport(do you need info about this as well?)
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pedro21101
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Post by pedro21101 » Sun Aug 21, 2005 7:36 am

Yes explain it please. About osmoregulation i read that active transport of Na ions outside of a cell is one of the main mechanisms how the cell can maintain osmotic balance between their protoplasm and outside environment. And also theres clearly written that with one Na ion which leave cell is always one molecule of water or maybe I didnt understand that text good. But the first statement about main functíon in osmo. is really true. :!:

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Post by sdekivit » Sun Aug 21, 2005 9:12 am

the Na/K-pump does relly play an important role in maintaining the osmotic value inside the cell. Because of the active transport of 3 Na-ions against only 2 K-ions, the chemical potential inside the cell increases compared with that of the environment and thus water flows out of the cell to let the cemical potential of the environment rise because of rising the pressure.

The contrary is possible too, be transporting less Na-ions outside the cell. This is very important for the cell. Because when this pump is inactivated, the cell's chemical potential would decrease so much that the flows so much water inside it, that the cell lyses. (osmotic pressure rises due to leaking of Na and Cl-ions --> osmosis occurs)

This is not the only feature of the Na/K-pump. The Na/K-pump is an ATP-ase and transports against the concentration gradient. By transporting extra Na outside, many transportmechanisms (for example the Na-dependant glucosetransport) will increase.Also aminoacids and Ca-ions flow inside the inside using Na-dependant transport.

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Poison
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Post by Poison » Sun Aug 21, 2005 4:37 pm

MrMistery wrote:You're wrong. :D :D :D :D :D


It's good to see you 'very very happy' Andrew... :lol: I'm glad, because I made it ... :D
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MrMistery
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Post by MrMistery » Sun Aug 21, 2005 7:41 pm

Lol... Well your post ended with "please correct me if i'm wrong" so i felt it was only adequate to start my post with "you're wrong" :D
About secondary active transport:
It uses the energy resulted from the lysis of ATP unly indirectly, not directly, under the form of using substances that have been put outside the cell by active means. It is generally discussed in pluricellular organisms. It transports more than one substance at a time, generally 2. It divides between:
-simport: the molecules transported go in the same direction(example: glucose is taken in the cell along with Na)
antiport: the molecules transported go in opposite directions(example: Ca is excreted from the cell while Na comes inside)
There are many simports/antiports that use Na from outside the cell, so you can see the key role of the Na/K pump in this system. Also there is the role stated by sdekivit
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