Transport in cells (diffusion, osmosis, active transport)

What you need to be able to do

• Explain diffusion as the net movement of particles from high → low concentration.
• Explain osmosis as the movement of water through a partially permeable membrane from a dilute solution to a more concentrated solution.
• Explain active transport as movement against a concentration gradient using energy.

Common mistakes

• Mixing up dilute/concentrated with high/low water potential (keep it simple: dilute = more water).
• Saying osmosis is about any particles — it’s specifically water.
• Forgetting active transport needs energy.

Quick self-check

1. Which processes need a membrane?
2. Which process needs energy?
3. What happens to an animal cell in a very dilute solution?