Question

What is cell surface to volume ratio and why is it important in cell functioning? i.e. Can it explain why cells are so small?

Answer 1

The surface of a cell is a medium between the exterior and interior environment of the cell. It is the site of exchange between the interior and exterior environment. Cells must be large enough to allow sufficient exchange so that the contents of the cell can be supported. Think of a sphere, if you increase it's surface, the volume increases as well.
Now lets take random figures as the radii of each circle
SA of largest circle with radii 4in= 201.1
Volume of largest circle with radii 4in= 268.08
Surface area: volume= 0.75

SA of middle circle with radii 2in= 50.265
Volume of middle circle with radii 2in= 33.510
Surface area: Volume= 1.5

SA of smallest circle with radii 1.2in= 15.08
Volume of middle circle with radii 1.2in= 7.238
Surface area: Volume= 2.08

Notice that as our Surface got bigger, the volume increased? But the Surface to volume ratio decreased? So therefore this ratio limits the size of cells.