Why is facilitated diffusion better than simple diffusion?

The key difference between simple diffusion and facilitated diffusion is that simple diffusion occurs without the involvement of channel or carrier proteins while the facilitated diffusion occurs through channel or carrier proteins.

Índice Show

What is Simple Diffusion?
What is Facilitated Diffusion?
What are the Similarities Between Simple Diffusion and Facilitated Diffusion?
What is the Difference Between Simple Diffusion and Facilitated Diffusion?
What is Simple Diffusion?
What is Facilitated Diffusion?
Similarities Between Simple Diffusion and Facilitated Diffusion
Difference Between Simple Diffusion and Facilitated Diffusion (Simple diffusion vs facilitated diffusion)

Simple diffusion is a process that transports molecules from a region of high concentration to a region of low concentration. It occurs along the concentration gradient. Hence it does not use energy. And, this process can be explained by a simple task where when you open a scent bottle, quickly its smell spreads throughout the room by diffusion.

Similarly, if you put an ink drop into a beaker filled with water, the colour will distribute evenly in the water. Diffusion not only occurs in those instances, but it also occurs in the cells as well. However, sometimes when larger molecules diffuse across the membrane, the proteins associating the membrane involve with the diffusion process. It is referred to as facilitated diffusion, and it differs from the simple diffusion since it involves the membrane proteins which are channels or carrier proteins. However, since both the simple diffusion and facilitated diffusion occur along the concentration gradient, both processes are passive processes.

1. Overview and Key Difference
2. What is Simple Diffusion
3. What is Facilitated Diffusion
4. Similarities Between Simple Diffusion and Facilitated Diffusion
5. Side by Side Comparison – Simple Diffusion vs Facilitated Diffusion in Tabular Form
6. Summary

What is Simple Diffusion?

Simple diffusion is a process that transports molecules from a region of higher concentration to a region of lower concentration in a solution or across a semi-permeable membrane. It is a passive process. In simple diffusion, molecules move without the aid of other molecules such as proteins or channel or carrier proteins.

Figure 01: Simple Diffusion

Simple diffusion passively occurs until all the molecules distribute evenly throughout the solution or between both sides of the membrane. Hence, this process stops when the equilibrium is reached. Since the simple diffusion does not occur through transmembrane proteins, it occurs via the phospholipid bilayer. Furthermore, simple diffusion can transport only small molecules.

What is Facilitated Diffusion?

Facilitated diffusion is a form of diffusion that facilitates the movement of molecules from a region of higher concentration to a region of lower concentration via transmembrane proteins. Since it also occurs along the concentration gradient, it is a passive process similar to simple diffusion. But, facilitated diffusion occurs through the proteins. Hence, it differs from the simple diffusion.

Figure 02: Facilitated Diffusion

Moreover, this process facilitates the uptake of nutrients across the cell membrane without utilizing energy. It uses channel proteins or carrier proteins of the membrane. Not only small molecules, but facilitated diffusion also facilitates the movement of larger molecules across the membrane as well. Similar to simple diffusion, facilitated diffusion occurs till the concentration is equal in both sides.

What are the Similarities Between Simple Diffusion and Facilitated Diffusion?

Simple diffusion and facilitated diffusion are passive processes that do not use energy.
Both processes occur along the concentration gradient.
Also, when equilibrium is reached, the molecular movements stop in both processes.
Furthermore, these processes occur in cells across the membranes.

What is the Difference Between Simple Diffusion and Facilitated Diffusion?

Simple diffusion occurs from a higher concentration to a lower concentration passively. Transmembrane proteins do not involve with the simple diffusion. On the other hand, facilitated diffusion also occurs from higher concentration to lower concentration passively. But transmembrane proteins aid the facilitated diffusion. Therefore, this is the key difference between simple diffusion and facilitated diffusion. Furthermore, simple diffusion takes place across the phospholipid bilayer while the facilitated diffusion takes place only across the membrane proteins. Such that, this is also a difference between simple diffusion and facilitated diffusion.

Another difference between simple diffusion and facilitated diffusion is that the simple diffusion can transport only smaller molecules while the facilitated diffusion can transport both the small and larger molecules across the cell membrane.

The below infographic summarizes the difference between simple diffusion and facilitated diffusion.

Simple diffusion and facilitated diffusion are two passive processes that allow molecules to distribute from higher concentration to lower concentration. The transmembrane proteins do not support simple diffusion. On the other hand, carrier or channel proteins aid the facilitated diffusion. Thus, it is the key difference between simple diffusion and facilitated diffusion. Furthermore, when considering the cell membrane, simple diffusion occurs via the phospholipid bilayer of the cell membrane while facilitated diffusion occurs via the transmembrane proteins. Thus, this is another difference between simple diffusion and facilitated diffusion. Simple diffusion allows small molecules to travel across the membrane while facilitated diffusion allows both small and larger molecule to pass through the membrane. Thus, this article summarizes the difference between simple diffusion and facilitated diffusion.

Reference:

1.“Facilitated Diffusion.” Wikipedia, Wikimedia Foundation, 6 Nov. 2018. Available here

Image Courtesy:

1.”Scheme simple diffusion in cell membrane-en”By LadyofHats Mariana Ruiz Villarreal – Own work. (Public Domain) via Commons Wikimedia
2.”Facilitated Diffusion”By Kjaray – Own work, (CC BY-SA 4.0) via Commons Wikimedia

The major distinction between simple and facilited diffusion is that simple diffusion is not accompanied by the involvement of the channel or carrier proteins whereas the facilitated one takes place through channels or protein carrier proteins.

The simple diffusion process is the method which transports molecules from a region with a high concentration to another that is low in concentration. It happens on the gradient of concentration. Therefore, it doesn’t require energy. The method can be explained with an easy task. If you open a bottle of scent and the scent spreads quickly across the entire room through diffusion.

Similar to this, if you place an ink drop in a beaker that is filled with water color is evenly distributed throughout the water. The process of diffusion is not limited to these situations however, it can also occur in cells as well. But, in some cases, when larger molecules are able to diffuse through the cell membranes, proteins associated with the membrane participate in the process of diffusion. This is known as Facilitated diffusion. It differs from simple diffusion because it involves membrane proteins, which are carriers or channels. In reality, both simple diffusion and the facilitated diffusion are based on the concentration gradient Both are non-passive processes.

What is Simple Diffusion?

Simple diffusion is an unassisted form of diffusion that occurs when particles are moved from greater to a lower concentration. The directional movement of the gradient of concentration is a passive process. When the molecules are evenly distributed, the molecules located on opposite side of the membrane reach an equilibrium in which there is no net movement of molecules is noticed. In general, non-polar molecules of small size such as carbon dioxide, oxygen and ethanol are able to freely move through the cell membrane. The rate of diffusion is dependent on molecular size, temperature and the intensity of the concentration gradient. The temperature affects the energy of the particles within the solution. Large particles will experience more resistance within the solution as compared to smaller particles. Furthermore in the event that concentration gradients are large there will be more molecules passing across the membrane.

What is Facilitated Diffusion?

Facilitated diffusion is the movement of substances across a membrane of a living organism via a concentration gradient using an underlying molecular. In facilitated diffusion, huge molecules and ions are dissolving in water and are specifically and in a passive manner transferred across cell membranes. Polar ions are transported through transmembrane channel proteins, and large molecules are transported through transmembrane-carrier proteins. Channel proteins form hydrophobic tunnels in the membrane, which allows selected molecules that are hydrophobic to pass across the membrane. Certain channel proteins are “open constantly and others like Ion channel proteins are “gated’. Permeases, the proteins that carry out transport, alter their shape as molecules such as amino acids or glucose move through them. Aquaporins are another type of transport proteins that permit water to pass through the membrane at such a speed.

Similarities Between Simple Diffusion and Facilitated Diffusion

Simple and facilitated diffusion occurs along the gradient of concentration from the highest concentration to small amount of molecules.
The two types of molecules do not require energy to facilitate the transport of molecules.
The net movement of molecules along each side of the membrane of the cell is 0 in equilibrium.

Difference Between Simple Diffusion and Facilitated Diffusion (Simple diffusion vs facilitated diffusion)

Facilitated diffusion vs simple diffusion

Characteristics	Simple Diffusion	Facilitated diffusion
Definition	Simple diffusion is one of the types of passive transport that, as its name implies, is the unaided movement of a substance that occurs when the electrochemical potentials on both sides of the permeable barrier differ.	Facilitated diffusion is the method of transport by biological organisms in which particular elements of the biological membrane interact with specific solutes or groups of solutes, significantly increasing the speed that they cross the membrane.
Driving Force	The primary force driving straightforward diffusion can be attributed to the concentration gradient that runs across the membrane.	The variation in the concentration of a substance across the membrane is the primary driving factor behind the diffusion of solute.
Energy requirement	Simple diffusion works as passive mode of transport which means it doesn’t need any energy.	Facilitated diffusion can also be an inactive transport mechanism that doesn’t require energy but certain facilitated diffusion processes may be active.
Speed	The speed of diffusion that is simple is relatively slow.	The rate of diffusion facilitated is generally more rapid.
Solute specificity	Simple diffusion is not solute-specific.	Facilitated diffusion is controlled by the difference in the solute and the carrier molecules.
Other forces	Apart from the concentration gradient, the kinetic energy produced by molecules also drive the simple diffusion.	In simple diffusion the process is governed by kinetic energy, in combination with the gradient of concentration.
Inhibition	Simple diffusion is not hindered by an inhibitory molecule.	Facilitated diffusion may be blocked by inhibitory molecules.
The direction of motion	In simple diffusion the motion of particles is accompanied by in the direction that the gradient of concentration is.	In diffusion that is facilitated the movement of molecules can take place in opposite directions and in the direction of the intensity gradient.
Molecule size	Simple diffusion is most often involved in the flow of non-polar molecules that are small in size.	Facilitated diffusion is usually involved in the transport of large molecules and polar ones across the biological membrane.
Channel proteins	Simple diffusion is molecules are moved or through the general or the surface	Certain channels are involved in facilited diffusion, which causes the formation of pores that are specifically designed for the transport of molecules.
Examples	The exchange of gas between blood and lungs as well as mixture of gas within the air, and the digestion of nutrients through bacteria are just a few examples of diffusion that is simple.	Transfer of ions such as potassium and calcium, the circulation of oxygen through the blood through the aid of hemoglobin and the movement in amino acids as well as glucose through blood to the cells are just a few instances of diffusion that is facilitated.