Why are cells so small?Wouldn't it make more sense for cells to grow to a larger size? That way, the human body could be made up of a few hundred large cells instead of trillion of tiny ones? And yet, the cell is considered to be an efficient system. Why are cells so small in size?

As an efficient, open system, the cell must be able to carry out all of the life processes. The transport of materials into and out of the cell is critical because these materials will determine how the other processes function.

The cell membrane is the barrier to free exchange between the outside environment and the cytoplasm. Whatever changes happen to the cell, the ability to transport materials must be kept at a maximum.

If a cell becomes larger and its volume increases, why is this a problem?

• • More molecules will need to be transported across the cell surface to take part in the cell's functions.

  • The distance any molecule has to travel from the cell surface will increase.

  • Food can’t get to mitochondria

  • Oxygen can’t reach the center

If the cell is to maintain its ability to transport substances, there must be a greater surface area to match the increased need for molecule transport.

In order to maximize the efficiency for diffusion across the cell membrane, cells must have a high Surface Area to Volume ratio

So.... We must look at how Surface Area changes in relation to Volume for different cell sizes.

Amount of area exposed on the surface. When talking about a cell, the surface area is the size of the cell membrane