(resting membrane potential) Why does the Na+/K+ pump move Na+ and K+ against their concentration gradients? Why is 3 Na+ out and 2 K+ in?

I did physics for my undergrad before Med so maybe I can chime in.

  1. You’re essentially investing the energy into establishing the gradient. Some transmembrane enzymes can use the established gradient for their function. Think maybe like neurons. The pump essentially takes the stored energy the cell has as ATP and converts it into an electrochemical gradient that is primed to provide energy for the movement of solutes that is an action potential.

  2. No. It is relatively MORE negative. But being more negative doesn’t mean having more negative charge. Like if the interior of the cell is at +4 and outside of the cell is at +10 (making these numbers up) there will be a ELECTRICAL POTENTIAL DIFFERENCE between the two areas. Voltage is something that is not really taught well and it took me years to realize that you can pretty much interchange it with potential energy. (It’s ok I grant you this power). So having two areas with different charges will create a potential DIFFERENCE (and therefore have potential energy).

  3. Arbitrary number that nature (or inset your Deity of choice) chose. It doesn’t matter that it was 3 to 2 it could have been 7 to 2. Or 2 to 1. As long as there’s a relative charge difference.

N.b. This is just one way cells store energy. You can do it electrochemically like with the na k pump. You can do it with pure concentration gradients too.

/r/medicalschool Thread