Diffusion
Diffusion is the random movement of a substance from a region of high concentrationThe measure of the amount of a substance. to a region of low concentration (ie: down the concentration gradient).
For example, oxygen moves from a high concentration in the lungs to a low concentration in the blood.
Substances (oxygen, carbon dioxide, water, dissolved nutrients and urea) can move into and out of a cell or organism via diffusion.
This happens across the cell membrane which is selectively permeableA substance which allows fluids or gases to pass through it..
Rate of diffusion
The rate of diffusion is affected by the:
- concentration gradientThe difference in concentration between two solutions, between different cells or between cells and a surrounding solution. - a larger difference in the high and low concentrations increases the diffusion rate.
- Temperature - a higher temperature provides the particles with more kinetic energyEnergy which an object possesses by being in motion. increasing the diffusion rate.
- Surface area - a larger surface area through which diffusion can happen increases the diffusion rate.