Question

As a cell grows, what happens to it's surface area:volume ratio? How is this changing ratio related to cell division.

Answer 1

As a cell grows, the surface area : volume ratio decreases. It means that, when a cell increases in size up to a certain limit, the surface area of the cell can't provide enough surface area for the exchange of materials across its membrane. At this stage the cell starts dividing, so that after cell division, the surface area: volume ratio will be normal. As after cell division, the surface area increases for a cell (as two cells are formed) and volume (of the internal cell materials) decreases, now the surface area of a cell can provide enough area for the exchange of materials.

As conclusion, as a cell grows the surface area: volume decreases, when it decreases upto a certain value, the cells starts dividing.