What is diffusion? The movement of elements from a higher concentration to a lower concentration region is called diffusion. This process is “Passive,” and it needs no energy; the gradient is more than enough to drive the process. There are two types of diffusion processes. They are Simple Diffusion and Facilitated Diffusion. 

What is Simple Diffusion? Simple diffusion is a type of passive transport of molecules which, as the name suggests, is merely unassisted by transmembrane.

What is Facilitated Diffusion? Facilitated diffusion is the spontaneous transport of molecules or ions across a cell’s membrane via specific transmembrane proteins.

Examples of both Simple and Facilitated type of diffusions

Simple Diffusion

The exchange of gases between lungs and blood, the mixing of gases in the atmosphere, and the absorption of nutrients by bacteria are some examples of simple diffusion.

Facilitated diffusion

Transfer of ions like calcium and potassium, movement of oxygen in the blood with the help of hemoglobin, and the transport of amino acids and glucose from the blood to the cell are examples of facilitated diffusion.

Similarity between Simple Diffusion and Facilitated Diffusion

Simple Diffusion: In simple diffusion, the membrane is freely permeable to the molecules, so their movement does not require energy utilization.

  • Simple diffusion is a type of passive transport, which means no energy is required.
  • Simple Diffusion work with the concentration gradient, which means go from a high concentration area to a low concentration area?

 Facilitated diffusion: In Facilitated diffusion, the membrane is not freely permeable to the molecule, for example – Hydrophilic substances, so their movement across the cell requires the presence of specialized proteins, which will help them to clear the plasma membrane barrier.

  • Facilitated diffusion is also a passive transport type, which means no energy is required.
  • Facilitated diffusion also works with the concentration gradient, and it also goes from a high concentration area to a low concentration area.

Differences between both Simple and Facilitated Diffusion:


  • The simple diffusion speed is relatively low.
  • Facilitated diffusion is somewhat higher in regards to the speed.

Size of Molecules

  • Simple diffusion is mostly occupied in the route of small non-polar molecules.
  • Facilitated diffusion is generally involved in the movement of large and polar molecules across a biological membrane.

Driving Force

  • Simple diffusion driving force is the concentration gradient across the membrane.
  • For facilitated diffusion, the distinction in the concentration of solute across the membrane is the driving force.

Solute specificity

  • The cycle of simple diffusion dissemination is not solute explicit.
  • Facilitated diffusion is directed by the specificity between solute and carrier molecules.

Energy requirement

  • No energy is required because a simple diffusion is a passive transport mechanism.
  • Facilitated diffusion is also a passive transport mechanism that doesn’t require any energy, but some facilitated diffusion processes can be active.

Additional forces

  • The kinetic energy of the molecules also drives the process of simple diffusion besides the concentration gradient.
  • As in simple diffusion, the process is driven by kinetic energy in addition to the concentration gradient.

Direction of movement

  • In simple diffusion, the movement of particles occurs along the direction of the concentration gradient.
  • In facilitated diffusion, molecules’ movement can occur both in direction and opposite of the concentration gradient.


  • An inhibitor molecule does not inhibit simple diffusion.
  • Specific inhibitor molecules can inhibit facilitated diffusion.

Channel proteins

  • In simple diffusion, the movement of molecules occurs either through the general surface of the membrane
  • Gated channel proteins, channel proteins, and the carrier proteins are main types of transport proteins that are convoluted in facilitated diffusion.

Dr. Ayesha Saeed is PhD in Biochemistry. She has been serving as a lecturer in different colleges for last 7 years. Currently, she is vice-principal in a privately owned medical college. She recently joined biomadam as a volunteer writer to share her knowledge through our platform.

Write A Comment

I accept the Privacy Policy

Pin It