A physiologist observes that the concentration of sodium inside a cell is decidedly lower than that outside the cell. Sodium diffuses easily across the plasma membrane of such cells when they are...

A physiologist observes that the concentration of sodium inside a cell is decidedly lower than that outside the cell. Sodium diffuses easily across the plasma membrane of such cells when they are dead, but not when they are alive. What cellular function that is lacking in dead cells explains the difference?

(a) osmosis

(b) diffusion

(c) active transport (solute pumping),

(d) dialysis.