Water (H2O), carbon dioxide (CO2), and oxygen (O2) are all quite small molecules, yet they move across cell membranes differently. Both CO2 and O2 passively diffuse across the cell membrane directly while H2O moves across the cell membrane by facilitated diffusion. What can be concluded about these three molecules based on the way they react to the cell membrane?

The amount of H2O the cell allows to cross the membrane must be more carefully controlled than the amounts of CO2 or O2.

The concentration of H2O is higher outside the cell and the concentrations of CO2 and O2 are higher inside

Question

Water (H2O), carbon dioxide (CO2), and oxygen (O2) are all quite small molecules, yet they move across cell membranes differently. Both CO2 and O2 passively diffuse across the cell membrane directly while H2O moves across the cell membrane by facilitated diffusion. What can be concluded about these three molecules based on the way they react to the cell membrane?

The amount of H2O the cell allows to cross the membrane must be more carefully controlled than the amounts of CO2 or O2.

The concentration of H2O is higher outside the cell and the concentrations of CO2 and O2 are higher inside