the spreading of the particles of a gas, or of any substance in solution, resulting in a net movement from a region where they are of a higher concentration to a region with a lower concentration
When does it occur?
occurs spontaneously due to the random movement of fluid particles - all gas, liquid or dissolved particles have kinetic energy of movement
Greater the difference in concentration, the...
the faster the rate of diffusion, due to the steeper concentration gradient
How big are the molecules?
Only relatively small molecules can diffuse through cell membranes eg amino acids but not proteins, sugars like glucose but not large carbohydrate molecules like starch
Oxygen and Respiration
oxygen required for respiration passes through cell membranes by diffusion.
Where does it occur?
Diffusion occurs in all mixtures of gases, liquids or solutions.
Anything dissolved in a solution can...
spread or diffuse if there is a difference in concentration ie a net transfer of the substance from one place to another eg through a cell membrane