Re: Do these ion pumps lower activation energy?

I think you are actually talking about two or three different things here.
There are ion pumps which require ATP to be hydrolyzed to pump an ion 
across the membrane, there are ion exchangers which exchange one or more of 
a certain ion on one side of the membrane for one or more ions on the other
side of the membrane; and there are ion channels which are usually 
selective for a certain type of ion and can be opened by a number of 
methods including voltage, ligand binding and constitutive avtivity.  These 
pumps you are reffering to I think are cation specific ligand gated ion 
channels.  To initiate a nerve impulse in a typical neuron, the voltage of 
the membrane must increase to a more positive potential (typically for 
-70mV to -40mV). The way this is accomplished is through the activatio or 
opening of ligand-gated ion channels which open in response to a 
neurotransmitter binding to the channel allowing cation into the cell and 
rasing the internal cation concentration thereby making the membrane 
voltage more positive and binding to the channel allowing cation into the 
cell and rasing the internal cation concentration thereby making the 
membrane voltage more positive and with enough channels being opened the 
threshhold for voltage-gated Na channel activation is reached and the 
action potential is fired.

Dmitri