EVERYDAY SCIENCE

Detailed explanation-1: -Water, carbon dioxide, and oxygen are among the few simple molecules that can cross the cell membrane by diffusion (or a type of diffusion known as osmosis ). Diffusion is one principle method of movement of substances within cells, as well as method for essential small molecules to cross the cell membrane.

Detailed explanation-2: -Osmosis is a type of simple diffusion in which water molecules diffuse through a selectively permeable membrane from areas of high water concentration to areas of lower water concentration.

Detailed explanation-3: -The ‘cell membrane’ (also known as the plasma membrane or cytoplasmic membrane) is a biological membrane that separates the interior of all cells from the outside environment. The cell membrane is selectively permeable to ions and organic molecules and controls the movement of substances in and out of cells.

Detailed explanation-4: -They are semi-permeable, which means that some molecules can diffuse across the lipid bilayer but others cannot. Small hydrophobic molecules and gases like oxygen and carbon dioxide cross membranes rapidly. Small polar molecules, such as water and ethanol, can also pass through membranes, but they do so more slowly.