Question

What are some examples of facilitated diffusion?

Answer 1

Any large or polar molecule usually requires facilitated diffusion and cannot cross the lipid bilayer via simple diffusion.

Explanation:

Since the outer and inner parts of the lipid bilayer are non-polar, polar molecules cannot be diffused across. For example, in order for a potassium ion to enter the cell, it must pass through a specialized transmembrane protein. These ions and molecules move down the concentration gradient and therefore requires no energy. Glucose is a large molecule that relies on transport proteins and the movement of sodium ions to enter the cell, instead of ATP.

Here is a discussion of how transport proteins such as channel proteins are involved in moving materials in or out of cells by the process of facilitated diffusion.

Video from: Noel Pauller

Hope this helps!