Surface are to volume ratio

[dufka]

hi guys !!

Can anyone explain me the importance of surface area to volume ratio in biology?? My teacher always gets away with explaing because she doesnt know herself. Its so funny but in result i dont understand biology (

[Cynthia]

Quoting from my study guide:

"As the size of an object is increased, the ratio between the surface area and the volume decreases. Consider the surface area to volume ratio of cubes of varying sizes as an example"

For example, a cube with 1 cm each side would have a surface area of 1x1x6=6 whereas the volume would be 1x1x1 = 1 -> surface area/volume = 6/1 = 6

A cube with 2 cm each side would have a surface area of 2x2x6=24 whereas the volume would be 2x2x2 = 8 -> surface area/volume = 24/8 = 3

And so on.

"The rate at which materials are used or produced depends on the volume. A cell that becomes too large may not be able to take in essential materials or excrete waste substances quickly enough." The same goes for heat - "Cells that generate heat may not be able to lose it quickly enough if they grow very large."

This is because the rate of exchange - diffusion/radiation - is directly affected by the surface area of an organism. As organisms grow both volume and surface area grow but volume grows more.

Edited August 15, 2010 by Cynthia

[dufka]

thank you honey :* !

so it means that the smaller the cell, the better for it . is that right?

[Cynthia]

In that sense yes as long as it can carry out all the necessary functions