Understanding:
• Particles move across membranes by simple diffusion, facilitated diffusion, osmosis and active transport
Diffusion is the net movement of molecules from a region of high concentration to a region of low concentration
- This directional movement along a gradient is passive and will continue until molecules become evenly dispersed (equilibrium)
- Small and non-polar (lipophilic) molecules will be able to freely diffuse across cell membranes (e.g. O2, CO2, glycerol)
The rate of diffusion can be influenced by a number of factors, including:
- Temperature (affects kinetic energy of particles in solution)
- Molecular size (larger particles are subjected to greater resistance within a fluid medium)
- Steepness of gradient (rate of diffusion will be greater with a higher concentration gradient)
Simple Diffusion Along a Concentration Gradient