Question

select the true statements. molecules diffuse across a cell membrane until they are all on one side. once equilibrium is reached, molecules stop crossing the cell membrane. equilibrium is reached when molecules have an equal concentration on both sides of the cell membrane. molecules move down their concentration gradient to reach equilibrium.

Explanation:

Molecules diffuse from high - to low - concentration areas (down the concentration gradient) to reach equilibrium where the concentration is equal on both sides of the cell membrane. At equilibrium, molecules continue to cross the membrane in both directions at equal rates. Molecules do not all end up on one side and do not stop crossing once equilibrium is reached.

Answer:

C. Equilibrium is reached when molecules have an equal concentration on both sides of the cell membrane.
D. Molecules move down their concentration gradient to reach equilibrium.