GCSE Biology A comparison table of diffusion, osmosis, passive & active transport characteristics, similarities & differences Doc Brown's GCSE biology exam revision study notes

GCSE level Biology exam revision notes on material transport

Transport: Part 8. Some comparisons: A comparison table of the characteristics of the processes of diffusion, osmosis and passive transport and active transport of materials in living systems

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INDEX of notes: Transport in organisms

(8) A comparison table of diffusion, osmosis and active transport characteristics

Mode of transfer	Substances being moved	Situation conditions	Requirements	Energy required?
Diffusion	Any soluble substance - dissolved gas, liquid or solid	From a higher to a lower concentration	Transfer of substances down a concentration gradient	No energy needed, example of passive transport
Osmosis	Water	From a dilute solution to a more concentrated solution	Water passing through a partially permeable membrane	No energy needed, example of passive transport
Active transport	Any dissolved substance	Transferring a substance from a lower concentration to a higher concentration	Moving substances against a natural diffusion concentration gradient through a partially permeable membrane	Uses protein carrier molecules and energy needed from ATP - respiration in the mitochondria

Phrasing: In the context of diffusion - from a higher to a lower concentration means transfer from ...

(i) a more concentrated solution to a more dilute solution,

or (ii) a higher/greater level/concentration of a gas to a lower/smaller level/concentration

Key points -

Based on the syllabus-specifications for students taking the UK AQA, Edexcel and OCR GCSE level biology examinations (~US grades 9-10 biology).

Side-by-Side Comparison Table

Feature	Diffusion	Osmosis	Active Transport
Definition	Net movement of particles from high to low concentration.	Net movement of water molecules from high to low water potential.	Movement of substances from low to high concentration.
Type of substance moved	Small molecules (e.g. O₂, CO₂).	Water only.	Ions, glucose, amino acids, etc.
Requires a membrane?	No (but may happen across membranes).	Yes — through a partially permeable membrane.	Yes — across a partially permeable membrane.
Direction of movement	Down a concentration gradient.	Down a water potential gradient (dilute → concentrated).	Against the concentration gradient.
Energy required?	❌ No	❌ No	✅ Yes — uses energy from ATP.
Involves carrier proteins?	Sometimes (in facilitated diffusion).	No	Yes — uses specific carrier proteins.
Biological examples	Gas exchange in lungs or leaves.	Water uptake in root hair cells; osmosis in red blood cells.	Mineral ion uptake in roots; glucose absorption in intestines.

Exam Tips

Always compare them based on energy use, direction of movement, and whether or not they need a membrane or proteins.

Use specific biological examples to back up your answer!

Keywords, phrases and learning objectives for this part on transport in organisms

Be able to compare, contrast and describe what the scientific terms diffusion, osmosis and active transport mean when used in biology.

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