Facilitated transport

Facilitated transport, also known as facilitated diffusion, is a type of passive transport that allows substances to cross cell membranes with the assistance of special transport proteins. This process is essential for the efficient transport of many substances in biological systems, particularly in cells where certain molecules cannot diffuse across the lipid bilayer of the cell membrane due to their size, charge, or polarity.

Mechanism

Facilitated transport occurs when specific molecules bind to protein carrier molecules on the exterior of the cell membrane. This binding changes the shape of the carrier protein, allowing the molecule to pass through the membrane and into the cell. This process is driven by the concentration gradient, with molecules moving from areas of high concentration to areas of low concentration.

Types of Facilitated Transport

There are two main types of facilitated transport: channel-mediated diffusion and carrier-mediated diffusion.

Channel-Mediated Diffusion

In channel-mediated diffusion, molecules move through a channel protein in the cell membrane. These channels are selective, allowing only certain types of molecules to pass through.

Carrier-Mediated Diffusion

In carrier-mediated diffusion, molecules bind to a carrier protein on one side of the cell membrane. The binding of the molecule causes the carrier protein to change shape and transport the molecule across the membrane.

Role in Cellular Function

Facilitated transport plays a crucial role in cellular function by allowing the transport of necessary molecules that cannot diffuse across the cell membrane unaided. This includes large, polar molecules like glucose and amino acids, as well as charged ions like sodium and potassium.

See Also

• Active transport
• Passive transport
• Cell membrane
• Diffusion

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