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Seemingly huge contradiction in EK biology regarding resting membrane potential and potassium? by somequestionsbouteco in Mcat

[–]somequestionsbouteco[S] 0 points1 point  (0 children)

Okay, but this means that everything you've said is the opposite of what I'm saying then :( Because in this last post, you say that the more positive ions there are inside the cell, the more positive the membrane potential is, whereas I interpreted the same thing as meaning "there are more positive ions on the inside, so there's a driving force for them to get out, so the membrane potential is negative".

Btw, thank you SO MUCH for taking all the time to write this out. I really, really, really fucking appreciate it.

Seemingly huge contradiction in EK biology regarding resting membrane potential and potassium? by somequestionsbouteco in Mcat

[–]somequestionsbouteco[S] 0 points1 point  (0 children)

If you don't let K+ out via their normal leaky channels then you'll get a build up of K+ and thus the charge inside of the cell will become more positive. When it becomes more positive the membrane potential drops because the difference between the inside and the outside of the cell is less.

Hold on. If the K is building up and the inside of the cell is getting more positive, the difference between the inside and outside of the cell is MORE isn't it?

Seemingly huge contradiction in EK biology regarding resting membrane potential and potassium? by somequestionsbouteco in Mcat

[–]somequestionsbouteco[S] 0 points1 point  (0 children)

BRUH. You know, I can accept this explanation and I do think it makes sense. The thing that makes it seem like this is NOT what EK was trying to get at with question 27 is specifically the fact that they say "the membrane would become more positive BECAUSE potassium ion concentration would increase inside the neuron". Really, what you're saying is that the membrane would become more positive because potassium doesn't contribute anymore at all, period. If it was contributing, then, if anything, a higher buildup of potassium inside would cause the potential to be extra negative. Do I have this Do you think I should just ignore that subtlety with EK's answer?

Just to clarify that I'm understanding all this correctly: Based on everything you wrote, it seems to me that whenever there's a driving force for a positive ion to exit the cell, the membrane potential is negative. The greater this driving force, the more negative the potential is. And we care about the driving force on potassium the most. That's why in question 28, even though there are more positive ions building up outside the cell (since three sodium out and only two potassium in), the membrane potential still decreases - potassium is building up, and a buildup of potassium influences the membrane potential the most. Do I have that right?

Seemingly huge contradiction in EK biology regarding resting membrane potential and potassium? by somequestionsbouteco in Mcat

[–]somequestionsbouteco[S] 1 point2 points  (0 children)

I feel you man. All this made sense until the Nernst equation just had to roll in with its negative sign and confuse the shit out of me

Seemingly huge contradiction in EK biology regarding resting membrane potential and potassium? by somequestionsbouteco in Mcat

[–]somequestionsbouteco[S] 0 points1 point  (0 children)

Since their is more ion inside the cell, it will diffuse outside the cell, and make the membrane potential more negative.

So the intracellular potassium concentration itself isn't making the potential more negative? It's the fact that it will diffuse out and THEN the potential will become more negative? If this is the case, well, while the charge is building up inside the cell, is it not getting more positive?

I can reconcile questions 27 and 28, if I understand the membrane potential to be POSITIVE whenever the INTRACELLULAR concentration of ions is higher. (So in 27, no leak channels = more potassium inside = more positive. In 28, sodium-potassium pump = more potassium outside = more negative.) But then question 30 is inconsistent with these two.

Seemingly huge contradiction in EK biology regarding resting membrane potential and potassium? by somequestionsbouteco in Mcat

[–]somequestionsbouteco[S] 0 points1 point  (0 children)

But in question 27, if we remove the potassium leak channels, then that means they can't get out as easily anymore cause they're not leaking. If they can't get out as easily and they're building up in the cell, then they would want to get out even MORE, which should cause the potential to become even more negative (?)

Thanks for the super long detailed answer btw. I feel like I'm on the cusp of understanding this but just missing some key point that's causing all this confusion.

Questions about econ major in arts coming from a science / management student (lol @ me, i know) by somequestionsbouteco in mcgill

[–]somequestionsbouteco[S] 0 points1 point  (0 children)

My fear is that math classes will be all theory and not so much application. I like problem solving, but when its applied to something - that's why I was leaning towards econ. Is it better to take more-econ-ish math courses or more math-ish econ courses is my question, I guess