What is diffusion?
The net movement of particles from a region of higher concentration to a region of lower concentration, down a concentration gradient.
Cambridge IGCSE (9–1) Biology 0970 (Extended) (2026–2028) · 3.1
Revise Cambridge IGCSE (9–1) Biology 0970 (Extended) (2026–2028) specification point 3.1, Diffusion, with free active-recall flashcards. Flip through the set or review every question and answer below.
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What is diffusion?
The net movement of particles from a region of higher concentration to a region of lower concentration, down a concentration gradient.
Why do molecules and ions move randomly?
They have kinetic energy.
How can random particle movement produce net diffusion between regions of different concentrations?
Particles move in both directions, but more move from higher to lower concentration than in the reverse direction.
Does diffusion require an additional energy supply?
No; diffusion occurs without an additional energy supply.
What two conditions allow a substance to diffuse across a cell membrane?
A concentration gradient exists, and the membrane permits the substance to pass.
What role does diffusion of gases and dissolved solutes play in organisms?
It helps organisms obtain substances they need and remove substances they produce.
In what direction does net diffusion occur across a cell membrane?
From higher to lower concentration, rather than in a direction determined by the cell.