Fig. 1. Diffusion
Membranes keep molecules concentrated.
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Fig. 2. Osmosis
A semi-permeable membrane allows solute to be concentrated inside cells (A). If cells are placed in a hypotonic solution, water will diffuse into the cell, causing it to swell (B). If a cell wall is not present, the cells will eventually burst (C).

Fig. 3.Differential Cell Charactistics