Question

oxygen and carbon dioxide are nonpolar molecules while water is a polar molecule. which of these can easily move across the cell membrane without needing facilitated diffusion? oxygen and carbon dioxide molecules water molecules

Explanation:

Cell membranes are made of a phospholipid bilayer. Nonpolar molecules like oxygen (\(O_2\)) and carbon dioxide (\(CO_2\)) can dissolve in the nonpolar lipid tails of the bilayer and move across by simple diffusion. Polar water (\(H_2O\)) molecules have more difficulty passing through the nonpolar region without facilitated diffusion (though small amounts can pass slowly by simple diffusion, but compared to \(O_2\) and \(CO_2\), \(O_2\) and \(CO_2\) move more easily without facilitated diffusion as per the question's emphasis on "EASILY").

Answer:

oxygen and carbon dioxide molecules