Example Problem

The hypothetical ion Adamantium $($ Ad $)$ carries a single positive charge charge $(\backslash (\backslash$mathrm$\{$Ad$\}^\{+\}\backslash )).$ Its extracellular concentration is $0\mathrm{.}1$ mM whereas the internal concentration is $10$ mM $.$

a$.$ First, consider the effect of concentration gradient. Does concentration gradient create a tendency to push Adamantium outside, or pull them inside? Briefly explain$/$illustrate$.$

b$.$ For the intracellular resting potential of $-90$ mV $,$ does the Electric field across the membrane have the tendency to push Adamantium outside, or pull them inside? Briefly explain.

c$.$ Calculate the Nernst potential for Adamantium at $300$K $($Remember that the Nernst potential is drawn with opposite polarity to the cell membrane potential; you should obtain a positive value$).$

d$.$ Draw the circuit diagram for Adamantium. The diagram should include a symbolic cell capacitance, the Nernst potential for this ion $($show polarity and value$),$ and the conductance path for the ion.

e$.$ The conductance of the channel $($in Siemens $\backslash (=1/\backslash$mathrm$\{$Ohms$\}\backslash ))$ as a function of the voltage difference across it is shown below. Assume that the concentration changes are negligible $($hence the Nernst voltage is constant$).$ When the membrane potential rises to $-70$ mV $,$ what would be the value of the ionic current for Adamantium?