This comparison covers Diffusion vs Osmosis vs Active Transport: Side-by-Side within Cell Transport for GCSE Biology. Diffusion, osmosis, active transport, factors affecting transport, surface area to volume ratio, and practical investigations It is section 11 of 19 in this topic. Use this comparison to connect the idea to the wider topic before moving on to questions and flashcards.
⚖️ Diffusion vs Osmosis vs Active Transport: Side-by-Side
Figure: Comparing the three types of cell transport
| Feature | Diffusion | Osmosis | Active Transport |
|---|---|---|---|
| What moves? | Any particles (gases, ions, small molecules) | Water molecules only | Specific molecules / ions (e.g. glucose, mineral ions) |
| Direction | High → Low concentration (down gradient) | Dilute → Concentrated (down water concentration gradient) | Low → High concentration (AGAINST gradient) |
| Energy required? | No — passive | No — passive | Yes — ATP from mitochondria |
| Membrane needed? | Not necessarily (can occur in air/water) | Yes — must be partially permeable | Yes — uses protein carrier molecules in membrane |
| Concentration gradient? | Required (high to low) | Required (low water concentration pulls water in) | Works against gradient |
| Body examples | O2 into blood at alveoli; CO2 out of cells | Water into root hair cells from soil; water reabsorption in kidneys | Glucose absorption in small intestine; mineral ions into root hair cells from soil |
| Plant examples | CO2 into leaf cells for photosynthesis | Water entering root cells from soil | Mineral ions (nitrate, phosphate) into root hair cells |
Practice questions for Cell Transport
Which statement best describes diffusion?
Explain how osmosis causes a plant cell to become plasmolysed when placed in a concentrated sugar solution.
Quick recall flashcards
Define osmosis
The movement of water molecules from an area of high water concentration (low solute concentration) to an area of low water concentration (high solute concentration) through a semi-permeable membrane.
Define diffusion
The movement of particles from an area of high concentration to an area of low concentration down a concentration gradient. No energy is required (passive process).