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Membrane Potential

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Membrane Potential

Postby Marc » Sat Sep 30, 2017 5:36 am

Hi,
I have been using the App Biology Academy https://play.google.com/store/apps/details?id=com.bucany.quiz for some time to prepare myself for my exams. Everything's fine so far. Only I don't quite understand the answer to the following question:
Question:
You are currently so enthusiastic about biology lessons that you are trying to measure the electrical voltage on Loligo forbesi a giant squid's axon yourself. For this purpose, you have a measuring and a reference electrode, both of which are connected to a voltage meter. You now insert both electrodes into the giant axon. What voltage do you measure?
A) 0mV
B)-70mV
C)-70V
D)-700mV

I would have said -70mV, the resting potential. But the app says, this would be the wrong answer, because both electrodes would be inserted into the cell (i. e. into the same medium) and you don't measure any potential, i. e. 0mV!

Do you understand that or did I miss something here? :?
Marc
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Re: Membrane Potential

Postby claudepa » Sun Oct 01, 2017 1:58 pm

It is true that the membrane potential is between the external part of the membrane (outside the cell) and the internal part of the membrane (Inside the cell). So if both electrodes are Inside the cell there no potential. The membrane potential comes from the fact that Na+, K+, CL- concentrations are different outside and Inside the cell.
claudepa
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