In a resting cell at room temperature (27 degree C, chloride, sodium and potassi

Question

In a resting cell at room temperature (27 degree C, chloride, sodium and potassium ion channels exist with a permeability ratio of 0.05:1:05. What is the membrane potential of this cell, H these ions are present in the concentrations then m the table below? Which ion species has the largest current density in this resting cell? Which ion species has the smallest current density in this resting cell? Explain your answers in one sentence each Sketch an electrical circuit representation of a single potassium (K^+) channel (assume a parallel RC circuit model' Label the components in your circuit and the intra and extracellular domains If the potassium channels represented m (c) exist within a cell at a resting potential of -70 mV. what is the current flowing through the potassium channels in this cell? Assume that the conductance of the potassium channel is 0.35times 10^-3 Ohm^-1.

Explanation / Answer

a) Membran potential according to Goldman-Hodgkin-Katz equation (GHK equation)

V= RT/ F ln (pK [K+]0 + pNa [Na+]0 + pCl[Cl-]i / pK [K+]i + pNa [Na+]i + pCl [Cl-]o)

pk = 5, pNa = 1, pCl = 0.05

T = 273 + 27 = 300 K, F= 96485 C mol-1   

V = 8.314* 300/ 96485 ln (5*5 + 1*145 + 0.05*150/ 5*150 + 1*15 + 0.05*110)

V = 0.026 ln(170.5/ 770.5)

V = 0.026 * -1.47

V = - 0.039 V = - 39.21 mV

b) K+ has largest cell density in the resting cell because K+ has highest intracellular concentration inside the cell. Cl- has lowest cell density inside the cell because Cl- has lowest intracellular concentration inside the cell.

d) I = V/ R = V (volt) x conductance (Ohm-1)

I = - 70 mV x 0.35 x 10-3 =2.45 x 10-5 A = 24.5 uA

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