Simple diffusion is the movement of molecules from an area of high concentration to low concentration without the need for energy until equilibrium is reached, such as the exchange of oxygen and carbon dioxide. Facilitated diffusion uses membrane proteins as carriers or channels to move molecules like glucose across the cell membrane and the number of carrier molecules limits the rate at which this process can occur.

1. A- Simple diffusion
 The movement of molecules from an area of greater concentration to one of lesser
concentration until equilibrium?? is reached.(concentration gradient)----Example (O2, Co2
Exchange )

2. B- Facilitated diffusion
 Facilitated diffusion uses membrane proteins that function as carriers or channels to move
molecules (such as glucose) across the cell membrane.
 The number of carrier molecules in the cell membrane limits the rate of this process.