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Unformatted text preview: The overall limit to cell size seems to be this surface area/volume ratio. As the volume of a cell increases, the cell has proportionally less surface to exchange nutrients, gases and wastes with its environment to sustain the increasing volume. Within the cytoplasm, materials move by diffusion, a passive physical process that can work only for short distances. A large volume would inhibit the rate of movement too much for cells to function. However, cells with minimal metabolic needs can have larger volumes. Some exceptions are: The yolk of a bird is a single cell. Some nerve cells run from the spine to the toes of mammals (although the diameter is small and they are microscopic, maintaining a good surface area to volume ratio.) Some green algae, such as Caulerpa and Acetabularia (Kingdom, Protista) have huge cells, and often are multinucleate....
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- Spring '10