2.2 Facilitated diffusion through channels Definition Some transport proteins have watery spaces all the way through the molecule allow free movement of certain ions or molecules. They are called channel proteins. Diffusion carried out by protein channel is termed channel mediated diffusion.33 2.2 Facilitated diffusion through channels ➢ Definition ➢ Some transport proteins ➢ have watery spaces all the way through the molecule ➢ allow free movement of certain ions or molecules. They are called channel proteins. ➢ Diffusion carried out by protein channel is termed channel mediated diffusion