Question

The membrance potential of a cell is -70mV. E_na is +65 mV , E_k =-95 mv , E_cl=-75 mV

A. If a Na channel were to open, in which direction would Na+ go? Is this a negative or positive current?

B. If A K channel were to open, in which direction would K+ go? Is this a negative or positive current?

C. If a Cl channel were to open, in which direction would Cl- go? Is this a negative or positive current?

Answer 1

Ecell=-70mV

ENa=65mV

EK=-95mV

ECl=-75mV

Ions move from its high potential to low potential region.Also the conventional direction of current is the direction of flow of positively charged ions.

A) As the potential of Na outside the Ecell is higher(more positive) than its membrane potential , so Na+ will move into the cell across the membrane. Positively charged Na+ is moving so it forms out the membrane (in flux of positive charge) forms a positive current inside the cell

B) Ek<Ecell, so K+ will move out of the cell.(outflux of K+) forming a negative current inside the cell.

C)ECl <Ecell, so Cl- will move out of the cell across the membrane.(outflux of Cl-).As the direction of current is the direction of positive charge, so this will form a positive current inside the cell.