CARRIER PROTEINS – bind to a specific type of diffusing molecule. They have a highly specific hydrophilic region to which the solute molecule binds. This binding cause the protein to undergo a change in shape that moves the solute across the bilayer and release it on the other side
In facilitated diffusion a point will be reached where increase in concentration differences are not accompanied by an increased rate. Why?
The system is saturated – there are only a limited number of carrier molecules per unit area of membrane. The rate of movement reaches a maximum when all the carrier molecules are fully loaded with solute molecules
The net movement of water molecules by diffusion from a solution of less negative water potential to a solution of more negative water potential through a partially permeable membrane.
Osmosis Osmosis is a “special kind of diffusion”. It’s when water diffuses from a concentrated area to a less concentrated area through a partially permeable membrane (i.e. one that allows water to move through but not anything else): Water Sugar solution In this example the water molecules will move from left to right (along the concentration gradient) and gradually dilute the sugar solution. This is how water moves into root hair cells