Can someone explain the Nernst Equation and its purpose, in as simple terms as possible? For some reason it's just not clicking with me. Thanks!
The Nernst equation is just used to measure the electrical potential, for the purposes of cell bio, it is used to measure the electrical potential of ions across the cell membrane. The Nernst equation can be written as followed:
E=(RT/zF)ln([K+]o/[K+]i)
[K+]i=ion concentration in cells
[K+]o=ion concentration outside cells
z= is the charge associated with the ion
F=Faraday's equation
R= Constant
T=Temperature in Kelvin
Awesome, that makes much more sense. Thank you! My book was rather hard to follow in this section.
Not a problem. Just beware of my typos; F= Faraday's constant, not equation.
Certainly! The Nernst Equation is a mathematical formula that relates the concentration of ions across a membrane to the electrical potential difference, or voltage, across that membrane. It specifically applies to situations where the system is at equilibrium, meaning there is no net ion movement.
The equation is often used to calculate the equilibrium potential for a specific ion across a membrane, such as in neurons or other cells. Specifically, it helps us understand how the movement of ions like sodium (Na+), potassium (K+), or chloride (Cl-) can create electrical signals in cells.
The Nernst Equation is as follows:
E = (RT / zF) * ln([ion]outside / [ion]inside)
Let's break it down:
- E represents the equilibrium potential for the ion across the membrane.
- R is the gas constant (8.314 J/(mol·K)).
- T is the temperature in Kelvin.
- z is the valence or charge of the ion.
- F is Faraday's constant (96,485 C/mol).
- [ion]outside and [ion]inside represent the concentration of the ion outside and inside the cell, respectively.
- ln represents the natural logarithm.
To use the Nernst Equation, you would plug in the values for R, T, z, and F, and then divide the concentration of the ion outside the cell by the concentration inside. Finally, take the natural logarithm of that ratio and multiply it by the other constants. The result is the equilibrium potential for that ion.
For example, if you wanted to calculate the equilibrium potential for potassium (K+) across a cell membrane at room temperature (25°C) where [K+]outside is 5 mM and [K+]inside is 100 mM, you would use the Nernst Equation as follows:
E = (0.0257 / 1) * ln(5/100)
E ≈ -0.082 volts
This negative value indicates that the inside of the cell is more negative relative to the outside, which is typically the case for many cells.
I hope this explanation helps! Let me know if you have any further questions.