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DNA Limits Cell SIze
A cell's nucleus contains all the information necessary for division into two identical cells. Deoxyribonucleic acid (DNA) is found in a cell's nucleus. DNA contains all the instructions necessary for cell division and ensures that the two cells resulting from mitosis--or the separation of a cell's chromosomes into two sets--are identical. DNA determines cell size because it "instructs" cells to grow to a specific size.
Diffusion Is a Passive Process
Diffusion is defined as the spontaneous movement of materials along a concentration gradient from an area of high concentration to an area of low concentration. The rate of diffusion across a cell's membrane is slow. As a cell grows, its surface area (membrane) does not increase in direct proportion to its volume.
Cell Surface Area to Volume Ratio
As cell size increases, surface area increases in micrometers squared; however, cell volume increases in micrometers cubed. This relationship determines how large cells can get. Since diffusion occurs slowly, the cell's surface area must be large enough to support its volume. If a cell gets too big, nutrients can no longer diffuse fast enough across the cell's membrane to support its volume.