What Characteristic is Shared by Simple Diffusion and Facilitated Diffusion?

The characteristic shared by simple diffusion and facilitated diffusion is that both are forms of passive transport. They move molecules from high concentration to low concentration across a membrane without requiring energy. The key difference is that facilitated diffusion uses carrier proteins, while simple diffusion does not.

Passive Transport and Concentration Gradient

Both simple diffusion and facilitated diffusion rely on passive transport, meaning they do not need ATP. They move molecules along the concentration gradient, from high concentration to low concentration naturally.

How Do They Work?

Cells use these processes to transport essential molecules, but they work differently.

• Simple Diffusion moves small, nonpolar molecules like oxygen (O₂), carbon dioxide (CO₂), and lipids directly through the phospholipid bilayer.
• Facilitated Diffusion transports larger or polar molecules such as glucose, amino acids, and ions using carrier proteins or channel proteins embedded in the membrane.

Key Characteristic Shared by Simple Diffusion and Facilitated Diffusion

Both processes share fundamental traits that help regulate cell function.

• No Energy Requirement: Both rely on passive transport and do not use ATP.
• Movement Along the Concentration Gradient: Molecules always move from high concentration to low concentration.
• Membrane Involvement: Both occur across the cell membrane to facilitate molecular exchange.
• Essential for Homeostasis: These processes help maintain the proper balance of substances inside and outside the cell.

Both simple diffusion and facilitated diffusion move molecules without energy input. The main difference is that facilitated diffusion requires carrier proteins, while simple diffusion does not.