If cell depolarises at +50mV, what are the concentrations of K+?
I am really confused how to use the nernst equation to get the concentrations. If I set up 58 [Kout]/[Kin] = 50, will that be right? I am not sure how to start this problem.
To determine the concentrations of K+ inside and outside the cell using the Nernst equation, you need to know the charge, temperature, and the equilibrium potential of K+. The Nernst equation relates these variables as follows:
E = (RT/zF) * ln([K+]out/[K+]in)
Where:
E is the equilibrium potential in volts
R is the ideal gas constant (8.314 J/(K*mol))
T is the temperature in Kelvin
z is the charge of the ion (for K+, it's +1)
F is Faraday's constant (96,485 C/mol)
[K+]out is the concentration of K+ outside the cell
[K+]in is the concentration of K+ inside the cell
Given that the cell depolarizes at +50mV, we can assume that the equilibrium potential of K+ is approximately +50mV.
1. Convert mV to V:
Equilibrium potential (E) = +50mV = +0.050V
2. Plug in the known values into the Nernst equation:
+0.050V = (RT/zF) * ln([K+]out/[K+]in)
Since you want to solve for the concentration of K+ inside the cell ([K+]in), you will need to rearrange the Nernst equation and solve for [K+]in:
3. Rearrange the Nernst equation and solve for [K+]in:
ln([K+]out/[K+]in) = (zF/RT) * E
Now that you know the new form of the equation, you can solve the problem. However, the values of R, T, and F should be known or provided. The temperature (T) is typically measured in Kelvin, the gas constant (R) is 8.314 J/(K*mol), and F is 96,485 C/mol. Substitute these values, along with the value of E, into the rearranged equation.
Keep in mind that this equation assumes that [K+]out is known, and you're solving for [K+]in. If you have additional information, such as the concentration of K+ outside the cell, you can substitute that value in and solve for [K+]in.