VPB 112: General Veterinary Biochemistry (1+1)

SIMPLE DIFFUSION

• A net movement (flux) of the solute from the region of higher concentration to one of lower concentration is called as diffusion.
• Diffusion occurs as downhill process. Higher the difference in concentration between two systems, the more rapid the rate of diffusion.
• Diffusion occurs either directly through the membrane or through membrane channels or through pores.  

• Diffusion of molecules across the membrane depends on charge, size and lipid solubility of the substance. Smaller the molecules, greater the rate of diffusion and more the lipid solubility, more the rate of diffusion.
• Diffusion of ions depends on the charge and concentration of the ions inside and outside the membrane.
• Small, uncharged molecules (such as O₂, CO₂ and H₂O) and lipid soluble substances (Such as steroid hormones) cross membranes by simple diffusion.
• It does not exhibit saturation kinetics.