Importance of diffusion to living organisms

Diffusion is important to cells because it allows them to gain the useful substances they require to obtain energy and grow, and lets them get rid of waste products.

This table shows examples of substances required by cell and associated waste products.

Substance required by cellWaste product of cell
GlucoseCarbon dioxide
OxygenUrea (made from excess amino acids)
Amino acids

The diagram below shows the differences in the concentrations of some of these substances between a cell and its environment and the direction that they diffuse.

Carbon dioxide: inside the cell - higher concentration of CO2, produced by aerobic respiration, arrow pointing from this to outside the cell where there's lower concentration of CO2.  Oxygen: outside cell - higher concentration, arrow pointing into cell were lower O2 concentration, used for aerobic respiration.  Amino acids: outside cell, higher concentration, arrow pointing into cell where lower concentration used to make proteins.