Diffusion
Diffusion
- Diffusion is the net movement of particles from higher to lower concentration.
- We say they move down a concentration gradient.
- It uses the particles' own random movement — no extra energy needed.
Practice
Diffusion is the net movement of particles:
Diffusion is down the concentration gradient (high → low) and needs no energy.
Why it matters, and what speeds it
- Many gases and solutes move by diffusion — e.g. oxygen diffuses in for respiration, carbon dioxide diffuses out.
- Diffusion is faster when:
- the surface area is larger,
- the temperature is higher,
- the concentration gradient is steeper,
- the distance (barrier) is shorter.
Practice
Diffusion is faster when:
Larger surface area, higher temperature, steeper gradient and shorter distance all speed diffusion.
Practice
Oxygen enters a respiring cell by:
Oxygen is at higher concentration outside, so it diffuses in for respiration; CO₂ diffuses out.
You've got it
Key idea
- diffusion = net movement of particles high → low concentration (down the gradient), needing no energy
- it moves gases and solutes (e.g. O₂ in, CO₂ out)
- faster with larger surface area, higher temperature, steeper gradient, shorter distance