Could you explain the difference between passive diffusion and facilitated transport?

Passive diffusion occurs without any transmembrane proteins being involved, the molecules cross the lipid bilayer following a concentration gradient (from the highest concentration to the lowest). Small uncharged molecules or hydrophobic ones cross this way (the best example is H2O).

Facilitated transport also involves a concentration gradient, however in this case the molecules cross the cell membrane through specific transmembrane proteins. These facilitate their passage, they are channels for the molecules (e.g. ions, glucose...).

Answered by Eleonore W. Biology tutor

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