Why Cells Are Small

Cells are the basic structural and functional units of life. As life on 
earth has evolved into organisms of varying complexities, two basic laws 
of nature have dictated why cells have remained so small.
 Shorter is 
faster. This is true both in terms of diffusion and in terms of chemical 
and electrical movement. By minimizing the the distance between a cellÕs 
nucleus and and the numerous proteins and organelles that it must 
constantly regulate , a cell is maximizing the speed in which 
intercellular communications can take place while providing the ideal 
conditions for diffusion: a vital function in the life of a cell. 
 Like 
wise, the surface area and volume of a cell are directly influential in 
the efficiency of the cellÕs nutrient absorption and waste expulsion 
processes. Since the cell membrane of a eukaryotic cell is its only 
source of nutrition, itÕs surface area must be large enough to allow the 
cellÕs organelles to receive the materia ls it needs. This is done by 
maximizing the surface area to volume ratio. By using the surface area 
and volume equations for a sphere(4¹r2 and 4/3¹r3) you can estimate the 
modeling the growth rate of the surface area and volume of a sphere on a 
linear graph itÕs easily discernible that as the size of the sphere 
increases the ratio of surface area to volume dramatically decreases 
until finally the volume of the sphere surpasses the surf ace area.
 
Simply, by minimizing its size, a cell is maximizing the speed at which 
it can communicate, the rate at which diffusion can occur, and the amount 
of surface area at itÕs disposal.