What is the basic difference between simple diffusion and facilitated diffusion across a cell membrane?

Simple diffusion and facilitated diffusion are both processes that allow substances to move across a cell membrane, but they differ in several key ways:

Simple Diffusion

• Mechanism: Simple diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration directly through the lipid bilayer of the cell membrane.
• Energy Requirement: It does not require energy (passive transport).
• Molecule Type: Typically involves small, nonpolar molecules like oxygen and carbon dioxide.
• Transport Proteins: Does not involve transport proteins.

Facilitated Diffusion

• Mechanism: Facilitated diffusion also involves the movement of molecules from an area of higher concentration to an area of lower concentration, but it requires the help of transport proteins embedded in the cell membrane.
• Energy Requirement: It is also a passive transport process and does not require energy.
• Molecule Type: Involves larger or polar molecules, such as glucose or ions, which cannot easily pass through the lipid bilayer.
• Transport Proteins: Utilizes specific transport proteins, such as channel proteins or carrier proteins, to facilitate the movement of substances.

Final Answer

The basic difference between simple diffusion and facilitated diffusion is that simple diffusion occurs directly through the lipid bilayer without the aid of transport proteins, while facilitated diffusion requires specific transport proteins to help move substances across the cell membrane.