Ion concentrations and equilibrium potentials

 

Ion	Inside	Outside	Equilibrium Potential
	(mM)	(mM)	$E_i = \frac{RT}{zF} \ln \frac{[C]_{out}}{[C]_{in}}$
Frog Muscle			$T\, = \, 20^\circ C$
K+	124	2.25	$58 \log \frac{2.25}{1.24} = -101mV$
Na+	10.4	109	$58 \log \frac{109}{10.4} = +59mV$
Cl-	1.5	77.5	$-58 \log \frac{77.5}{1.5} = -99mV$
Ca2+	10-4	2.1	$29 \log \frac{2.1}{10^{-4}} = +125mV$
Squid Axon			$T\, = \, 20^\circ C$
K+	400	20	$58 \log \frac{20}{400} = -75mV$
Na+	50	440	$58 \log \frac{440}{50} = +55mV$
Cl-	40-150	560	$-58 \log\frac{560}{40-150} = -66\hbox{ to }-33mV$
Ca2+	10-4	10	$29 \log \frac{10}{10^{-4}} = +145mV$
Mammalian cell			$T\, = \, 37^\circ C$
K+	140	5	$62 \log \frac{5}{140} = -89.4mV$
Na+	5-15	145	$62 \log \frac{145}{5-15} = +90-(+61)mV$
Cl-	4	110	$-62 \log \frac{110}{4} = -89mV$
Ca2+	10-4	2.5-5	$31 \log \frac{2.5-5}{10^{-4}} = +136-(+145)mV$