Facilitated diffusion via carrier proteins

Some molecules, such areas carbon dioxide, and oxygen can diffuse directly across the plasma membrane, but others have required assistance to cross its hydrophobic core. The Molecules diffuse that were across the plasma membrane with the help of membrane proteins such as channels and carriers in facilitated diffusion.

Because these molecules have a concentration gradient, they can diffuse into (or out of) the cell by moving down it. However, because they are charged or polar, they are unable to cross the phospholipid portion of the membrane on their own. Facilitated transport proteins protect these molecules from the hydrophobic core of the membrane, allowing them to cross. Channels and carrier proteins are the two major types of facilitated transport proteins.

What is Facilitated diffusion?

The passive movement of substances, such as biological molecules or ions, across a plasma membrane, using a transport protein located in the plasma membrane, is defined in biology as facilitated diffusion. Chemical energy is not used or required because substances move from higher to lower concentrations.

Carrier proteins

Carrier proteins are another type of transmembrane protein involved in facilitated transport. Carrier proteins can change shape to transport a target molecule from one side of the membrane to the other.

Carrier proteins, like channel proteins, are typically selected for one or a few substances. They frequently change shape in response to the binding of their target molecule, with the molecule moving to the opposite side of the membrane as a result of the shape change. The carrier proteins involved in facilitated diffusion simply allow hydrophilic molecules to move down a concentration gradient that already exists (rather than acting as pumps).

Material is transported at different rates by channel and carrier proteins. Channel proteins, in general, transport molecules much faster than carrier proteins. This is because channel proteins are simple tunnels; unlike carrier proteins, they do not need to change shape and “reset” each time a molecule is moved. A typical channel protein may facilitate diffusion at tens of millions of molecules per second, whereas a carrier protein may only work at a thousand or so molecules per second.

Characteristics of Facilitated diffusion

One of the many types of passive transport is facilitated diffusion. This is a type of cellular transport in which substances move along a concentration gradient. 

The disparity in concentrations between areas creates a gradient, which causes substances to naturally move to be distributed between the two areas to achieve equilibrium. Chemical energy is not directly required because the movement is downhill (from higher to lower concentrations). Kinetic energy, like that of other types of passive transport, drives facilitated diffusion. 

However, what distinguishes facilitated diffusion from other types of passive transport is the requirement for assistance from a transport protein lodged in the plasma membrane.

Facilitated diffusion Vs Simple diffusion