Why Cell is Small in Size?

Most cells are small and can be seen only with the aid of a microscope. (Exceptions include the eggs of most vertebrates [fishes, amphibians, reptiles, and birds] and some long nerve cells.) One reason for the smallness of cells is that the ratio of the volume of the cell’s nucleus to the volume of its cytoplasm must not be so small that the nucleus, the cell’s major control center, cannot control the cytoplasm. Another aspect of cell volume works to limit cell size. As the radius of a cell lengthens, cell volume increases more rapidly than cell surface area. The need for nutrients and the rate of waste production are proportional to cell volume. The cell takes up nutrients and eliminates wastes through its surface plasma membrane. If cell volume becomes too large, the surfacearea- to-volume ratio is too small for an adequate exchange of nutrients and wastes.