Cell size

Why are cells so small?



Simply put, it's to be efficient.


Since nutrients enter through the surface of the cell, it makes sense that cells are small for efficiency's sake. A smaller cell has more area to absorb nutrients and more area to expell waste, in relation to it's inside area.

As a shape gets bigger, the volume gets larger in relation to its surface.

The example from my notes says:

"As cells get larger, the amount of surface area in relation to volume decreases.

...a cube with 1mm sides has a surface area of 6mm2 and a volume of 1mm3. This gives a surface area to volume of 6:1.

A larger cube with sides of 2mm has a surface area of 8mm2 and a volume of 24mm2. This gives a surface area to volume ratio of 3:1."

So, it would make sense that cells are small.

Other reasons I have picked up around the web and paraphrased here (but are for fun- these aren't being taught in my class (yet)):


1. Many processes in the cytoplasm (cell inner 'filling' for lack of a better term) are achieved by diffusion. If a cell was large, it would take a longer time for nutrients and processes to make their way around the cell. This goes back to the efficiency reason for cell size.

2. If you’re painting a huge picture the smaller your brush is the more detail you will have. This makes a lot of sense! it's a pretty cool reason, actually!

3. This probably reiterates what I said above but I hear that we have billions of small cells because our cells need to be specialized into liver cells, blood cells, brain cells etc.


next up: Organelles!