Question

Why cells are small?

Answer 1

Cells are generally small in size because of two main reasons.
1. Different regions of a cell can communicate with each other rapidly for the cell to function effectively.
2. Cells have a large surface area/volume ratio for greater diffusion of substances in and of the cell.

To understand this second advantage about surface area/volume ratio imagine a cube with each of its sides measuring 2mm. The total surface area of this cube will be 2 mm*2mm*6(surfaces) =24 sq. mm.

Suppose we cut this cube into 8 equal smaller cubes by reducing each side by half its length, then the total surface area of these 8 smaller cubes will be 1 mm*1mm*6(surfaces)*8 mm =48 sq. mm, which is double that of the original larger cube.

The total volume in both cases still remains the same.

Smaller size of the cell presents a larger surface area/volume ratio.

The larger surface area relative to volume of the cell ensures greater diffusion of:

• nutrients into the cell,
• metabolic wastes from the interior to the outside of the cell,
• respiratory gases i.e. oxygen into the cell and carbon dioxide out of the cell.
• Any damage to the cell, can be easily repaired.