Taking Nernst for a test drive
Well, that was a lot of work, but we finally have a way of calculating the equilibrium potential based on the concentration gradient of an ion.
Let's give this equation a run for its money. Remember the typical cell? And remember that the cell's membrane is generally only permeable to potassium (K+)? So...
What is the Nernst potential associated with the potassium ion?
- I need a hint: This problem is basically plug-and-chug
- ... another hint ... : put the values of [K+]out and [K+]in into the equation
- ... another hint ... : like this: V = 62 log(5/140)
- ... another hint ... : get your calculator out ! please please please !
I think I have the answer: -90 mV
Bet you thought that was going to be harder... Let's try another one
What is the Nernst potential associated with the sodium ion?
- plug and chug!: [Na+]out is 145 and [Na+]in is 10
- ... another hint ... : your calculator is your friend!
I think I have the answer: +72 mV
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