Is surface area to volume ratio a factor in limiting cell size? why? how?

Question

- What are all the factors limiting cell size?
-Is SA:V a factor in limiting cell size? how?

Answer 1

The factors limiting cell size include:

1. surface area to volume ratio
As cells get larger, the volume increases at a faster rate than the surface area. So in a larger cell there isn't enough area of plasma membrane to handle all the diffusion and active transport that the inside of the cell needs to be healthy.

2. rate of diffusion
Diffusion is too slow to move materials into and out of the interior of a large cell. Parts of the cell are just too far away from the membrane and the extracelluar environment to get everything they need by diffusion.

3. amount of DNA
DNA has to direct the formation of all the cell's proteins. A larger cell would need a lot more protein, but it would still have the same amount of DNA. The DNA can't be transcribed fast enough to send enough mRNA messages to run a large cell.

Answer 2

All BUT 'Elasticity of the plasma membrane' are factors which limits cell size. The plasma membrane is not elastic, rather it is fluid with some rigidity due to the cytoskeleton. On the other hand the following DO limit cell size: Diffusion is a function of time and distance (and temeperature and concentration). Cells require diffusion of essential nutrients and water inward and of byproducts and waste outward. The time required for diffusion does limit the size of cells. If diffusion was infinitely fast, then the large distances of a big cell would not matter. Very large cell will have limitations in essential diffusion of nutrients in and byproducts out thereby limiting size The surface of the cell is important to faciliate the transport of substances in and out. As the size increases surface area (function of radius squared) to volume (fxn of radius cubed) decreases dramatically and limits the exchange of nutrients and byproducts which come across the membrane by faciltated or active transport (since these carriers will become limited relative to cell volume). A single nucleus may be too far from the more distant parts of a cell which has become too large, and thereby fails to sustain all the protein synthetic (mRNA synthesis in the nucleus) requirements of a very large cell.