1. a) Using the Nernst equation, calculate the equilibrium potential of the K+ i
ID: 3476293 • Letter: 1
Question
1. a) Using the Nernst equation, calculate the equilibrium potential of the K+ ions for the classic physiological preparation, the squid giant axon, where the concentration of K+ on the inside of the neuron is 400 mM and the concentration on the outside of the neuron is 20 mM. Make sure to round up and use negative (-) or positive (+) and the units.
b)The distribution of Na+ on the extracellular side of a neuron is 440 mM and on the inside is measured as 50 mM. Using the Nernst equation, calculate the equilibrium potential of Na+ and select the correct answer.
c) Using the Nernst equation, calculate the equilibrium potential of Cl- given an extracelullar concentration of 560 mM and an intracellular concentration of 150 mM. Make sure to use negative (-) or positive (+) and the units.
Explanation / Answer
Nernst Equation is V Eq = RT/ZF X log [ conc OUT/conc IN ]
RT/ZF value can be calculated using the following values
R = Gas constant, 8.135 J K-1 mol-1
T = temperature in K (273 + temp in oC) ,we consider room temperature 25 here, so 298K
Z = Charge of ion, which is 1 for Na+ and K+ and -1 for Cl-
F = Faraday’s constant, 9.684 x 104 C mol-1
It comes approx to 58mV which we will use for calculating the equilibrium potential for all the three ions (-58 for Chlorine, since Z is -1 for Cl).
a) For K+
V eq = 58 X log [ 20/400]
= 58 X log 0.05
= 58 X -1.301
= - 75 mV (minus 75)
b) For Na+
V eq = 58 X log [ 440/50]
= 58 X log 8.8
= 58 X 0.944
= 55 mV
c) For Cl-
V eq = - 58 X log [ 560/150]
= - 58 X log 3.73
= - 58 X 0.57
= - 33mV (minus 33)
Related Questions
Navigate
Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.