Compared to small cells large cells have more trouble


Why are cells so small?	Cells are so small that you need a microscope to examine them. Why? To answer this question we have to understand that, in order to survive, cells must constantly interact with their surrounding environment. Table of Contents Show What problems do larger cells have? Why is a small cell better than a big cell? Why do smaller cells have an advantage?

	Gases and food molecules dissolved in water must be absorbed and waste products must be eliminated. For most cells, this passage of all materials in and out of the cell must occur through the plasma membrane (see diagram above). Each internal region of the cell has to be served by part of the cell surface. As a cell grows bigger, its internal volume enlarges and the cell membrane expands. Unfortunately, the volume increases more rapidly than does the surface area, and so the relative amount of surface area available to pass materials to a unit volume of the cell steadily decreases.

	Finally, at some point, there is just enough surface available to service all the interior; if it is to survive, the cell must stop growing.
Surface Area to Volume Ration	The important point is that the surface area to the volume ratio gets smaller as the cell gets larger. Thus, if the cell grows beyond a certain limit, not enough material will be able to cross the membrane fast enough to accommodate the increased cellular volume. When this happens, the cell must divide into smaller cells with favorable surface area/volume ratios, or cease to function. That is why cells are so small.
BIOdotEDU © 2001, Professor John Blamire

What problems do larger cells have?

If the cell grows too large, the plasma membrane will not have sufficient surface area to support the rate of diffusion required for the increased volume. In other words, as a cell grows, it becomes less efficient.

Why is a small cell better than a big cell?

The large surface area to volume ratio of small cells makes the transport of substances into and out of cells extremely efficient. Another reason for the small size of cells is that control of cellular processes is easier in a small cell than in a large cell. Cells are dynamic, living things.

Why do smaller cells have an advantage?

Cells are small because they need to be able to diffuse through materials easily. Also, smaller size of the cells allows the passage of materials inside and outside of the cell easily. Cells are small in size to allow easy division and growth of the cells.