IGCSE Biology glossary
Concentration gradient
Biology editorial review is supported by the named review panel. Reviewer participation may vary by guide. Checked against Cambridge IGCSE Biology 0610 (2026–2028); last reviewed August 2026.
Definition
The difference in concentration of a substance between two regions. Diffusion occurs down a concentration gradient (from higher to lower concentration), while active transport moves substances against the concentration gradient (from lower to higher concentration).
What to include in an exam answer
Use 'down the concentration gradient' for diffusion and 'against the concentration gradient' for active transport. These directional phrases are key mark-scoring terms.
Example in context
Distinguish between diffusion and active transport in terms of the concentration gradient (2 marks): Diffusion moves substances down the concentration gradient from high to low concentration, while active transport moves substances against the concentration gradient from low to high concentration.
Related syllabus topic
Movement into & out of cells