Example of diffusion in an animal cell
The cells in our body need glucose and oxygen for respiration. Both these are carried in the blood. When blood reaches the cells the molecules of glucose and oxygen diffuse out of the blood and into the cells.
As cells use up the glucose and oxygen they produce waste chemicals and carbon dioxide. If these were to build up in the cells they would poison them, therefore they diffuse out of the cells into the blood.
Another example of diffusion in animal cells is the exchange of carbon dioxide and oxygen between the alveoli in the lungs and the blood. See gaseous exchange.