What is the difference between simple and facilitated diffusion?

Simple diffusion occurs when molecules move across a semi-permeable membrane without the need for a protein channel. Facilitated diffusion, on the other hand, requires the assistance of a protein channel to move molecules across the membrane.

Facilitated diffusion is a type of passive transport, meaning it does not require energy input from the cell. The protein channels involved in facilitated diffusion act as gatekeepers, allowing only certain molecules to pass through. These channels are specific to certain molecules, meaning they will only allow certain substances to pass through.

In contrast, simple diffusion occurs when molecules move from an area of high concentration to an area of low concentration. This process does not require any assistance from proteins and occurs naturally due to the random movement of molecules.

Facilitated diffusion is often used by cells to transport large or charged molecules, such as glucose or ions, across the membrane. Simple diffusion is typically used for small, non-polar molecules like oxygen and carbon dioxide.

Overall, while both simple and facilitated diffusion involve the movement of molecules across a membrane, facilitated diffusion requires the assistance of a protein channel while simple diffusion does not.