most extra cellular environments contain a high concentration of sodium ions (Na+). consider a cell membrane that is permeable to potassium (K+) and is in equilibrium. the diffusion of K+ has left the inside of the ell slightly negatively charged and the outside slightly positively charged. suppose that the cell membrane now opens some sodium channels what happens? A) there is no flow across the membrane. the outside of the cell is positeely charged drivingthe sodium ions father away from the cell. B) there is no flow across the membrane. the cell is in equilibrim and so the electric repulsionof the Na+ exactly counters the effects of diffusion. C) the cell becomes positvely charged. both diffusion and the electric attraction to the cell drive into the cell D) the cell becomes positvely charged; diffusion is reversed and K+ are drived back into the cell Solution The cell becomes positively charged, diffusion is reversed and K+ are drived back into the cell..

1. most extra cellular environments contain a high concentration of sodium ions (Na+). consider a
cell membrane that is permeable to potassium (K+) and is in equilibrium. the diffusion of K+ has
left the inside of the ell slightly negatively charged and the outside slightly positively charged.
suppose that the cell membrane now opens some sodium channels what happens? A) there is no
flow across the membrane. the outside of the cell is positeely charged drivingthe sodium ions
father away from the cell. B) there is no flow across the membrane. the cell is in equilibrim and
so the electric repulsionof the Na+ exactly counters the effects of diffusion. C) the cell becomes
positvely charged. both diffusion and the electric attraction to the cell drive into the cell D) the
cell becomes positvely charged; diffusion is reversed and K+ are drived back into the cell
Solution
The cell becomes positively charged, diffusion is reversed and K+ are drived back into the cell.