Answer:
Diffusion, osmosis and active transport are three similar chemical methods by which single molecules or very small structures are moved across membranes or relatively short distances, often within or between cells.
Explanation:
The movement of substances in and out of cells is a very important part of biology as without it no cell and so no organism could live very long. Substances can only cross the protective cell membrane by diffusion, osmosis or active transport. Mass flow only works at the organ, tissue and whole organism level.
