What is the Difference Between Simple Diffusion and Facilitated Diffusion?

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Simple diffusion and facilitated diffusion are both forms of passive transport, meaning they do not require energy to occur. They involve the movement of small particles from a location of higher concentration to a region of lower concentration. The main differences between simple diffusion and facilitated diffusion are:

  • Membrane Channels: In simple diffusion, the substance passes directly between the phospholipids in the cell membrane. In contrast, facilitated diffusion involves specialized membrane channels that help guide the molecules through the cell membrane.
  • Molecule Size and Polarity: Simple diffusion is typically used for small, non-polar molecules that can easily fit between the phospholipids in the cell membrane. Facilitated diffusion, on the other hand, is used for larger or polar molecules that cannot fit between the phospholipids and require the assistance of carrier proteins.
  • Carrier Proteins: Simple diffusion does not require carrier proteins, as the molecules can move directly through the cell membrane. In facilitated diffusion, carrier proteins bind to the target molecules, allowing them to pass through the cell membrane. After the molecule has entered the cell, the carrier protein releases it and returns to its original position, ready to transport another molecule.

In summary, simple diffusion is the movement of small, non-polar molecules directly through the cell membrane, while facilitated diffusion involves the use of carrier proteins to guide larger or polar molecules through specialized membrane channels. Both processes are forms of passive transport, meaning they do not require energy to occur.

Comparative Table: Simple Diffusion vs Facilitated Diffusion

The main differences between simple diffusion and facilitated diffusion are as follows:

Characteristic Simple Diffusion Facilitated Diffusion
Definition Simple diffusion is a type of passive transport that occurs when there is an unassisted movement of solute based on its electrochemical potentials across a permeable barrier. Facilitated diffusion is a type of biological transport that involves the movement of particles with the help of a carrier molecule or channel proteins.
Speed Simple diffusion is relatively slow. Facilitated diffusion is comparatively faster than simple diffusion.
Molecule Size Simple diffusion is involved in the passage of small and non-polar molecules. Facilitated diffusion is commonly involved in the movement of large and polar molecules.
Carrier Molecules Simple diffusion does not require the assistance of a carrier molecule. Facilitated diffusion requires the assistance of a carrier molecule or channel protein.
Solute Specificity Simple diffusion is not solute-specific. Facilitated diffusion is always solute-specific.
Inhibition The simple diffusion process cannot be inhibited by an inhibitor molecule. The facilitated diffusion process can be inhibited by an inhibitor molecule.

In summary, simple diffusion is a slow, unassisted process that occurs for small and non-polar molecules, while facilitated diffusion is a faster, assisted process that involves large and polar molecules. Carrier molecules or channel proteins are necessary for facilitated diffusion, and it can be inhibited by inhibitor molecules.