Does the cell membrane allow something to move out of cell?

1 Answer
Dec 20, 2016

Cell membrane is selectively permeable: hence it may allow 'something' to move out when concentration of that thing is lower on the outside, by a process called diffusion . List of such things is short: water, oxygen and carbondioxide are such materials.


Diffusion of water across cell membrane is called osmosis. Act of diffusion does not require expenditure of energy. Sometimes a carrier protein may be required for diffusion; it is then called facilitated diffusion.

Cell membrane also pumps out ions against concentration gradient, e.g. sodium but such acts are ATP dependent.