What is osmosis? Osmosis is the diffusion of water molecules from a region of  higher concentration (dilute solution) to a region of lower concentration (concentrated solution) through a partially permeable membrane. Note that a partially permeable membrane allows small molecules such as water to pass through but not large solute molecules.

Each cell is surrounded by a cell membrane. It separates the contents f the cell from the outside. The cell membrane has tiny holes in it which allows small molecules to pass through but not large ones. Te cell membrane is described as being partially permeable.

Osmosis is a special kind of diffusion involving water molecules. It occurs when two solutions are separated by a partially permeable membrane.

Osmosis is the diffusion of water from a dilute solution into a more concentrated solution through a partially permeable membrane.

The tiny holes in the membrane allow small water molecules to pass through, but the large solute molecules are too big to pass through the partially permeable membrane. Water is diffusing from a place where there is a dilute solution with a high concentration of water to a place where there is a concentrated solution with a low concentration of water.

Water potential is a way of thinking about the ability of water to move by osmosis. This is influenced by how much water is available, but also by other factors such as the pressure exerted on water in plant cells by the cell wall. It is more accurate to say that a dilute solution (containing a lot of water molecules) has high water potential. A concentrated solution (containing fewer water molecules) has a low water potential.


Back in 9th grade, I did an experiment which explored diffusion. Below is link to a copy of my (embarrassing, yet simultaneously informative) lab report from 2 years ago.


A cute Apparatus/Materials picture:

Rachel Putri Utomo
Block F, Honors Biology
Mr. Kevin Quick
Academic Year 2013-2014