Biology - Osmosis

  • Created by: Dan_23
  • Created on: 16-05-21 10:23

Osmosis is the diffusion of water molecules, from a region where the water molecules are in higher concentration, to a region where they are in lower concentration, through a partially permeable membrane.

A dilute solution contains a high concentration of water molecules, while a concentrated solution contains a low concentration of water molecules.

Osmosis refers to the movement of water molecules only.

The slideshow shows an example of osmosis showing the direction of movement of water between two different concentrations of sugar solutions.

The process of osmosis

Step one

The beaker contains water and sugar molecules

When the concentration of water is the same on both sides of the membrane, the movement of water molecules will be the same in both directions. There will be no net movement of water molecules. In theory, the level of solution two will rise, but this will be opposed by gravity and will be dependent on the width of the container.

Similar observations will be made with solutions containing different solutes, for instance, salt instead of sugar.

Osmosis across living cells

Cells contain dilute solutions of ionssugars andamino acids

The cell membrane is partially permeable.

Water will move into and out of cells by osmosis.

Plant cells

Isolated plant cells placed in a dilute solution or water will take


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