Question

OSMOSIS, most comprehensive over view possible please!

Answer 1

General definition of osmosis: the flow of water through a semipermeable membrane from an area of high concentration to an area of low concentration.
My visual example: you're inside at a crowded party and you need some air because it is getting WAY too crowded, so you step through the door into a second, less-crowded room. Other people from the first room who feel that they are also too crowded step through the door too, until there is an equal number of people in the first room and second room.
Explanation: just like the people in the crowded room, water (and other substances) want to be as spread out as possible. If you have two areas separated by a membrane or layer that only lets water through it, the water is going to go through that membrane until it is as spread out across both sides as possible.
Hope this 1am answer helps a little.

Answer 2

Osmosis is the movement of solvent molecules through a selectively-permeable membrane into a region of higher solute concentration, aiming to equalize the solute concentrations on the two sides. It may also be used to describe a physical process in which any solvent moves, without input of energy, across a semipermeable membrane (permeable to the solvent, but not the solute) separating two solutions of different concentrations. Although osmosis does not create energy, it does release kinetic energy and can be made to do work, but is a passive process, like diffusion.

Net movement of solvent is from the less-concentrated (hypotonic) to the more-concentrated (hypertonic) solution, which tends to reduce the difference in concentrations. This effect can be countered by increasing the pressure of the hypertonic solution, with respect to the hypotonic. The osmotic pressure is defined to be the pressure required to maintain an equilibrium, with no net movement of solvent. Osmotic pressure is a colligative property, meaning that the osmotic pressure depends on the molar concentration of the solute but not on its identity.

Answer 3

Osmosis is important in biological systems, as many biological membranes are semipermeable. In general, these membranes are impermeable to organic solutes with large molecules, such as polysaccharides, while permeable to water and small, uncharged solutes. Permeability may depend on solubility properties, charge, or chemistry, as well as solute size. Water molecules travel through the plasma cell wall, tonoplast (vacuole) or protoplast in two ways, either by diffusing across the phospholipid bilayer directly, or via aquaporins (small transmembrane proteins similar to those in facilitated diffusion and in creating ion channels). Osmosis provides the primary means by which water is transported into and out of cells. The turgor pressure of a cell is largely maintained by osmosis, across the cell membrane, between the cell interior and its relatively hypotonic environment.

Answer 4

Osmosis is water moving through a thin material that will let small molecules pass through, but larger molecules cannot get through it (permeate).