Question

which phrase best defines diffusion?

movement through a cell membrane using energy from atp

active transport of particles up a concentration gradient

movement of particles from a region of high concentration to a region of low concentration

movement of particles from a region of low concentration to a region of high concentration

Explanation:

To determine the best definition of diffusion, we analyze each option:

• The first option describes active transport (uses ATP), but diffusion is passive (no energy from ATP), so this is incorrect.
• The second option mentions active transport and moving up a concentration gradient, which is not diffusion (diffusion is passive and down the gradient), so this is incorrect.
• The third option: Diffusion is the passive movement of particles from an area of high concentration to an area of low concentration (down the concentration gradient) due to random motion. This matches the definition of diffusion.
• The fourth option describes movement against the concentration gradient, which is active transport (like in the case of pumps), not diffusion.

Answer:

C. movement of particles from a region of high concentration to a region of low concentration