Why are cell so small?
Why are cells so small?
To answer this question we have to understand that, in order to survive, cells must constantly interact with their surrounding environment.
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.
I think John's answer came from this website.
http://www.brooklyn.cuny.edu/bc/ahp/LAD/C5/C5_ProbSize.html
Cells are small in order to maximize their efficiency and functionality. The small size allows for a larger surface area-to-volume ratio, which means that substances can enter and leave the cell at a faster rate.
To understand why cells are small, we need to delve into the concept of surface area-to-volume ratio. Surface area refers to the area of the cell's outer membrane, while volume refers to the space inside the cell. As a cell increases in size, its volume grows faster than its surface area. This ratio is important because a larger surface area allows for more interactions and exchange of substances with the external environment.
Let's consider a cell as a sphere for simplicity. As the diameter of a sphere increases, its volume increases with the cube of the radius (d^3), while its surface area increases with the square of the radius (d^2). This means that as a cell grows in size, its volume (internal contents) expands rapidly compared to its surface area.
If a cell were to become too large, it would face problems with exchanging materials and waste with its surroundings. Nutrients, gases, and other essential substances would struggle to diffuse across the membrane sufficiently and in a timely manner. Additionally, waste products would accumulate inside the cell, hindering proper functioning.
By staying small, cells maximize their surface area relative to their volume. This ensures efficient exchange of materials with the environment, allowing cells to acquire nutrients, eliminate waste, and support critical cellular processes more effectively.