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gh1991 gh1991
wrote...
Posts: 108
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13 years ago
the cells of your body have Na+-K+-ATPases,
which use energy from ATP to pump Na+ out of the cell and K+ into the cell. One
result of this is that there is an electrochemical gradient of Na+ ions
across the plasma membrane, with more Na+ outside than inside the cell.
-->given this gradient, in which direction will Na+ ions move spontaneously?
-->if they would move spontaneously in one direction, why don’t they quickly come
to equilibrium, with roughly equal concentration on each side
of the plasma membrane?
PLEASSEE HELP
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wrote...
13 years ago Edited: 13 years ago, sarah
Thanks for joining gh1991.

Q1 Sodium will have a tendency to move inside the cell.

Q2 Depends on the permeability of the membrane. Moreover, for every three sodiums that move out, 2 potassium ions move in, so it is impossible to accomplish equilibrium. You are using active transport which requires energy, in the form of ATP, to go against the concentration gradient.

Check out the following links for more clarification.

http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120068/bio03.swf::Sodium-Potassium%20Exchange%20Pump

http://highered.mcgraw-hill.com/olcweb/cgi/pluginpop.cgi?it=swf::535::535::/sites/dl/free/0072437316/120107/bio_a.swf::Sodium-Potassium%20Exchange
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