Permeability depends on solubility, charge, or chemistry, as well as solute size. In general, these membranes are impermeable to large and polar molecules, such as ions, proteins, and polysaccharides, while being permeable to non-polar or hydrophobic molecules like lipids as well as to small molecules like oxygen, carbon dioxide, nitrogen, and nitric oxide. Osmosis is a vital process in biological systems, as biological membranes are semipermeable. Osmotic pressure is a colligative property, meaning that the osmotic pressure depends on the molar concentration of the solute but not on its identity. Osmotic pressure is defined as the external pressure required to be applied so that there is no net movement of solvent across the membrane. It may also be used to describe a physical process in which any solvent moves across a selectively permeable membrane (permeable to the solvent, but not the solute) separating two solutions of different concentrations. Osmosis ( / ɒ z ˈ m oʊ s ɪ s/, US also / ɒ s-/) is the spontaneous net movement or diffusion of solvent molecules through a selectively-permeable membrane from a region of high water potential (region of lower solute concentration) to a region of low water potential (region of higher solute concentration), in the direction that tends to equalize the solute concentrations on the two sides. The blue dots represent particles driving the osmotic gradient. The process of osmosis over a semi-permeable membrane.

Osmos nutrition