Simple Diffusion vs Facilitated Diffusion

The movement of molecules from the plasma membrane with the help of transporter protein such as carrier is called as facilitated diffusion. However, in simple diffusion, there is movement of the molecules, but they don’t require the assistance of membrane proteins, and takes place due to the electrochemical difference between the two sides.

The gradient concentration is required in simple diffusion for the driving force to act, whereas in facilitated the solute concentration variation through the membrane is the driving force responsible for facilitated diffusion.

Although majority of facilitated diffusion does not suffice the need of ATP, however in few cases it does require ATP. But in simple diffusion there is no ATP need in this passive transport type of simple diffusion. Facilitated diffusion take place due to the exactitude between the carriers and the solute, however there is no selectivity of solutes in simple diffusion.

The speed is quite high in facilitated diffusion, whereas in simple diffusion its quite low. Inhibitors cannot stop the simple diffusion, whereas in facilitated diffusion it is possible due to distinct inhibitors.

Kinetic energy along with concentration gradient helps to carry out simple diffusion and similarly in facilitated diffusion. In facilitated diffusion molecules can progress in both the direction i.e., towards or against the concentration gradient.

However, in simple diffusion, the shift is restricted towards the gradient. The molecules which can pass through are water soluble huge molecules through the plasma membrane in facilitated diffusion, whereas in simple diffusion, tiny water-soluble molecule can pass through.

Channel proteins are not required in simple diffusion as they can diffuse through membrane surface, whereas they are required in facilitated diffusion resulting pores development and molecules can progress.

Example of facilitated diffusion are movement of substances like amino acid and glucose from blood to cell, in the blood transportation of oxygen, and various ions like calcium and potassium. In simple diffusion, fusing of atmospheric gases, taking up of nutrients by microorganism, gases swapping taking place between the blood and lungs are some examples.