Difference Between Diffusion and Facilitated Diffusion

Facilitated diffusion and diffusion are 2 types of the passive transport systems in which substance is transported in the cell by the help of cell membrane. Move the molecules with a greater concentration to a lower concentration with the aid of natural entropy until the concentration is equalized.

Diffusion vs Facilitated Diffusion

The main difference between diffusion and facilitated diffusion is that diffusion occurs when the substance propagates from greater to a lower concentration through a membrane without the need of a carrier molecule, whereas facilitated diffusion occurs when substances are transported across the cell wall via the use of a carrier molecule through a concentration gradient.

Diffusion vs Facilitated Diffusion

Diffusion is a type of diffusion in which substances propagate from a greater concentration to a lower concentration without the assistance of other particles. After the molecules have been uniformly disseminated, molecules on both areas of the cell membrane approach the state of evenness and hence no sharp movement of the particles can be observed.

Facilitated diffusion is carried out by Using a carrier molecule and concentration gradient. Chemicals are transported through a biological membrane via facilitated diffusion. polar molecules and Large ions dissolve in water and are transported through the cell membrane in a controlled and passive way by the method of facilitated diffusion. It diffuses at a quicker rate.

Comparison Table Between Diffusion and Facilitated Diffusion

Parameters of ComparisonDiffusionFacilitated Diffusion
VelocityThe rate of diffusion is very slow in normal diffusion It has a faster diffusion rate as compared to normal diffusion.
ForcesDiffusion is determined by the concentration gradient which is present across the membrane.The driving force is the pressure difference in the concentration of solute in the membrane.
OccurrenceIt occurs via phospholipid bilayer It occurs via transmembrane proteins
Diffusion RatesDiffusion depends on the gradient of concentration in the cell wall and the rate of diffusion.The kinetics of vector-mediated transport determine the rate of facilitated diffusion.
TransportationDiffusion moves non-polar and tiny particles.It transports polar and large particles.

What is Diffusion?

Solvent density is critical to the transport of solutes in the cell’s cytoplasm. Diffusion occurs when a chemical moves from a higher percentage of the solution to a low percentage solution area until its concentration is equal throughout a space. Small non-polar atoms, like carbon dioxide, ethanol, and oxygen. They generally pass readily through the cell membrane.

The rate of diffusion is affected by molecule size and the slope formed by the concentration gradient. It is one of the body’s methods for regulating chemical concentrations. As a result, the optimum or optimal concentrations of such compounds in the body may not be obtained right away. As cytoplasm density increases, the movement of molecules and gases slows, while the converse is true for less dense cytoplasm. The molecules on each side of the cell membrane attain an equilibrium in which there is no net movement of molecules after they are equally spread.

The size of the molecules has an impact on the rate of diffusion through a biological membrane. If the molecules are large, they will have a harder time migrating over the membrane, lowering the molecule’s diffusion rate. Lipid-soluble molecules, such as those found in the plasma membrane, can move quickly across a lipid layer.

What is Facilitated Diffusion?

Some molecules, such as carbon dioxide and oxygen, can diffuse straight through the plasma membrane, but others require assistance to pass its hydrophobic core. In assisted diffusion, molecules migrate across the plasma membrane with the aid of membrane proteins such as channels and carriers. The transfer of ions like potassium and calcium and the propagation of oxygen in the blood through hemoglobin and the propagation of glucose and amino acids in the blood to the cell are all instances of facilitated diffusion.

Because these molecules have a concentration gradient, they can diffuse into (or out of) the cell by traveling along with it. However, because they are charged or polar, they are unable to traverse the phospholipid portion of the membrane on their own. The energy barrier associated with the carrier’s conformational shift is often greater than the activation energy of solvent viscosity, which influences diffusion through channel proteins. Temperature causes carrier transport rates to grow more rapidly. Facilitated transport proteins protect these molecules from the hydrophobic center of the membrane, allowing them to pass.

Facilitated diffusion is used to carry out important cellular operations such as the transfer of oxygen, nutrients, and ions, which are required to maintain optimum homeostasis in the cell. Channels and carrier proteins are the two primary types of assisted transport proteins.

Main Differences Between Diffusion and Facilitated Diffusion

  1. Diffusion allows only tiny and nonpolar molecules to pass through the plasma membrane, whereas facilitated diffusion allows big and polar molecules to flow through.
  2. In case of Diffusion the Particles propagate in the direction of the concentration gradient, while atoms can travel in both directions — the opposite way and the direction of concentration gradient.
  3. Diffusion is unaffected by inhibitor molecules, whereas certain inhibitor molecules can prevent aided diffusion.
  4. Diffusion does not require energy from ATP so is a non-energy-consuming mode of transportation whereas facilitated diffusion may or may not require energy from ATP.
  5. Diffusion happens straight through the cell membrane whereas facilitated diffusion is facilitated by transmembrane integral proteins, which are specialised facilitator molecules.


The transfer of molecules in diffusion, as well as facilitated diffusion forms, does not necessitate the use of energy. Simple diffusion allows molecules to go directly through the cell membrane. Transmembrane proteins like channel proteins, aquaporins, carrier proteins, and on the other hand, facilitate diffusion. Simple diffusion transports small nonpolar atoms.

Diffusion facilitates the transfer of big and polar molecules. In the equilibrated condition, the total propagation of atoms on both sides of the cell wall is zero. we see how diffusion occurs in both simple and assisted forms down the concentration gradient. In the equilibrated condition, the net movement of molecules on both sides of the membrane of the cell is 0.


  1. https://journals.physiology.org/doi/abs/10.1152/physrev.1990.70.4.1135
  2. https://www.sciencedirect.com/science/article/pii/S0021925818969656
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