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.
