Supercharge your learning!

Use adaptive quiz-based learning to study this topic faster and more effectively.

Diffusion

Diffusion is the net (overall) movement of particles from an area of high concentration to an area of lower concentration.

When you put a drop of red dye into a glass of water, the dye diffuses until it is at equal concentration everywhere in solution.

A difference in concentration of a particle between two areas is called a concentration gradient. Diffusion occurs down a concentration gradient.

Diffusion is a passive process; it does not require energy.

Diffusion is fundamental to how organisms function:

  • Proteins diffuse within the cytoplasm of cells.
  • Carbon dioxide diffuses from the air into cells in the leaf for photosynthesis.
  • Oxygen diffuses from the blood into tissues for respiration.

Organisms can control concentration gradients to determine the direction of diffusion.

Molecules diffuse in random directions, but the net movement is from high to low concentration.
Molecules diffuse in random directions, but the net movement is from high to low concentration.