The process of diffusion is extremely important for the uptake of substances into cells. These substances can be very important for a whole range of cellular processes. Its also useful in reomoving waste products produced by cells themselves. Diffusion is particularly during gas exchange. In respiring cells, oxygen must be taken up into cells to be used in respiration whilst carbon dioxide must be removed as a waste product. However, in photosynthesising plant cells, the opposite also occurs also as carbon dioxide must be taken up into the cell and oxygen should be expelled as a product.Other important substances to be absorbed are nutrients such as amino acids glucose and most importantly, water