The membranes of vertebrate red blood cells (RBCs) can find various examples of facilitated transport by carrier proteins. For example, one RBC carrier protein carries in each direction a different molecule: Cl–in one direction and HCO3–in the opposite direction. In transporting carbon dioxide in the blood, this carrier is important.
The characteristic of selective channel transport is that its rate is saturable. In other words, if a substance's concentration gradient is gradually increased, it will also increase its transport rate to a certain point and then level off. Further gradient increases will not result in any additional rate increases. The scientific explanation for this kind of observation is that the membrane contains a limited number of carriers.
|Sl. No.||Simple Diffusion||Facilitated Diffusion|
|1||Simple diffusion does not require a carrier molecule's assistance.||Facilitated diffusion can only take place with the help of a carrier molecule.|
|2||Simple diffusion speeds are relatively slow.||The speed of diffusion facilitated is relatively fast.|
|3||Simple diffusion is not specific to the solution.||Facilitated diffusion is always a specific solution.|
|4||A molecule inhibitor cannot inhibit the simple process of diffusion.||Specific inhibitors that bind to the carrier molecules can inhibit the facilitated diffusion.|
|5||Simple diffusion is a passive process.||Facilitated diffusion can be an active or passive process.|
|6||Simple diffusion does not require ATP's energy.||Facilitated diffusion may require or may not require ATP energy.|
|7||The molecules can only pass in the direction of the concentration gradient in simple diffusion.||The molecules can pass in the direction and opposite of the concentration gradient in facilitated diffusion.|
|8||Simple diffusion allows the passage through the plasma membrane of only small and non - polar molecules.||Facilitated diffusion allows large and polar molecules to pass through the plasma membrane.|