On which side of a selectively permeable membrane does osmosis exert pressure?

Answer 1

A selectively permeable membrane (also known as a differentially permeable membrane or a semi-permeable membrane) is permeable to the solvent but not to solutes.

In cells, the solvent is always water.

All cell membranes (such as plasma membranes and vacuole membranes) are selectively permeable.

This means that water can cross these membranes by osmosis. This will happen when the total concentration of solutes on one side of the membrane is different from that on the other side.

The process is passive (requiring no energy input) and you can think of it as being an attempt by nature to "even up" the difference. Water passes into the stronger solution, i.e. the one with the higher concentration of solutes. If equilibrium is reached, the process will stop.

One example of the importance of osmosis: mature plant cells contain a central vacuole, holding an aqueous solution of various chemical compounds. These solutes create an osmotic pressurethat attracts water, swelling the vacuole and giving the cells turgor. The turgor of cells in well-watered plants holds up soft parts like leaves. If a plant lacks water, the vacuoles shrink and the leaves wilt.

Answer 2

as Osmosis pressure on the hypertonic side of a selectively permeable membrane

Answer 3

The side with a higher concentration of water or, for short, the hypertonic side.