How are simple diffusion and facilitated diffusion similar?

• A. Both processes involve the movement of molecules down their concentration gradient.
• B. Both processes require energy input from the cell.
• C. Both processes move molecules against their concentration gradient.
• D. Both processes require the presence of transport proteins.

Answer: (A)

Verified step by step guidance

1. Understand the concept of diffusion: Diffusion is the movement of molecules from an area of higher concentration to an area of lower concentration, down their concentration gradient.
2. Identify the characteristics of simple diffusion: Simple diffusion does not require energy input from the cell and does not involve transport proteins. It occurs directly across the phospholipid bilayer of the cell membrane.
3. Identify the characteristics of facilitated diffusion: Facilitated diffusion also moves molecules down their concentration gradient but requires the presence of transport proteins to help molecules that cannot easily pass through the cell membrane.
4. Compare the energy requirements: Both simple diffusion and facilitated diffusion do not require energy input from the cell, distinguishing them from active transport processes.
5. Summarize the similarities: Both simple diffusion and facilitated diffusion involve the passive movement of molecules down their concentration gradient, but facilitated diffusion requires transport proteins, while simple diffusion does not.