Comparing diffusion, osmosis and active transport

In animals, plants and microorganisms, substances move into and out of cells by diffusion, osmosis and active transport.

ProcessDescriptionsSubstances movedEnergy required
Diffusion Substances move from a high to a low concentration down a concentration gradientCarbon dioxide, oxygen, water, food substances, wastes, eg ureaNo
OsmosisWater moves from a high to a low concentration across a partially permeable membrane and down a concentration gradientWaterNo
Active transportSubstances move against a concentration gradientMineral ions into plant roots, glucose from the gut into intestinal cells, from where it moves into the bloodYes

A gradient is a slope. The diagram below shows the direction of movement of particles by diffusion, osmosis and active transport on a concentration gradient.

The direction of movement of particles by diffusion, osmosis and active transport on a concentration gradient.
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