Which direction will H^+ move across the membrane when V_m = -70 mV Why? Which d

Question

Which direction will H^+ move across the membrane when V_m = -70 mV Why? Which direction will Mn^++ move across the membrane when V_m = -70 mV? Why? Which direction will H^+ move across the membrane when V_m = -15 mV? Why? Which direction will Mn^++ move across the membrane when V_m = -15 mV? Why? Which direction will H^+ move across the membrane when V_m = 80 mV? Why? Which direction will Mn^++ move across the membrane when V_m = 80 mV? Why? At what membrane potential will net H^+ current be zero? At what membrane potential will net Mn^++ current be zero? What would the RMP be for this cell if the membrane contained 500 H^+ leak channels and 150 Mn^++ leak channels? What equation?

Explanation / Answer

Equilibrium potential of ions as calculated by Nernst equation is,

VEq = RT/ZF x ln [(ECF concentration)/(ICF conecentration)]

where,

R is universal gas constant (8.314 J/K/mol), T is temperature in Kelvin, Z is valency of the ion, F is faraday's constant (96485 C/mol).

VEq for H+ ion = (8.314 x 273) / 1 x 96485) x ln (2.7/0.15)

= 0.0235 x ln (18)

= 0.0235 x 2.89

= 0.067

VEq for Mn++ ion is = (8.314 x 273) / 2 x 96485) x ln (1.9/14.8)

= 0.0117 x ln (0.128)

= -0.0117 x 2.05

= -0.023

Electromotive driving force Vdf = Vm - VEq

So,H+ ion will move from ECF to ICF when Vm is -70 mV as well as when Vm is -15 mV because net Vdf is inward

Similarly, Mn++ ion will move from ECF to ICF when Vm is -70 mV as well as when Vm is -15 mV because net Vdf is inward

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