Question

3) A channel is permeable to both sodium and potassium. If the external cation concentrations are 110 mM Na and 5 mM K, and the internal concentrations 10 mM Na and 110 mM K, and the sodium conductance is one quarter of the potassium conductance, what is the reversal potential of the channel?

Answer 1

Given: - [Na^+]_out = 110 mM [K^+]_out = 5 mm [Na^+] _in = 10 m M [K^+]_in = 110 mM gno = 1/4 gk (g rightarrow conductivity) to find: reversal potential of the channel (nearest potential) solution: - for on ion A z plusminus E_AZ plusminus = RT/Z- plusminus F in [A_z plusminus]_out/[A_Z plusminus]_in where R rightarrow gas constant T rightarrow temperature F rightarrow faraday's Z^plusminus rightarrow choragic on goldman n equation (reversal potential) e_men/channel = E n sigma (g n sigma/g n sigma + g k) + E (g k/gn sigma + gk) T = 298 k (standard conditions) R = 8314 jk ^-1 mol^-1: F = 96485.33 c mol^-1 z plusminus = t 1 (for both na^+ & k^+) by substituting given data & values for T, z plusminus, F & R , we can show that: - E_na^+ = + 63.52 mv E_na^+ & E_k^+ = -81.88 mv substituting E_na^+ & gno = 1/4 gk (given)