AP Biology 3.4 Free Energy and Molecular Building Blocks. Why is the surface area to volume ratio of cells important?
|AP Biology||Free Energy and Molecular Building Blocks|
|Test Prep||AP Biology|
the exchange of materials between the cell and its environment is just oh so wrong.
The ratio between the surface area and volume of cells has a gigantic impact on the behavior,
physiology and other qualities of their environment.
Like when your lungs expand and contract to take in oxygen and release carbon dioxide. [lungs expanding and contracting]
So, breathe easy, Shmoopers, Answer D is incorrect. [a couple with their arms out wide on a beach]
Answer C is also suspect.
Size and shape affect the ability of diffusion to supply the demands of the cell.
Having an equal surface area-to-volume ratio would inhibit the necessary flow of materials
across plasma membranes.
Cells need breathing room to diffuse more oxygen and take in the nutrients they crave. [a cell struggling to breathe]
Answer C is not the ratio that cells have in mind for a peaceful existence.
So is a smaller surface area to volume ratio better than a large ratio?
Or is it better the other way around?
Remember that surface area is very important to cell function because everything the cell [Inside of a cell with arrow showing nutrients enter here]
could possibly want makes its way through the cell membrane.
As the size of a cell decreases, the ratio of surface area to volume increases. [a green cell decreasing in size]
As a result, small cells are more efficient at diffusion because of their high surface [one green cell multiplies into 5 cells]
area to volume ratio.
A long, thin cell like a nerve cell is a perfect example of efficiency.
On the other side of the coin, when a cell increases in size, the surface area expands [A green cell increasing in size]
at a lower rate than the volume.
Based on that, the correct answer is B, the larger the ratio, the better the cell is at
exchanging material with its environment.
It also explains why protozoa should never be the size of a school bus. [A protozoa bus picking up school girls]
They would starve to death because they would have a hard time getting enough oxygen, water
and nutrients transported across their plasma membranes. [Gigantic cell destroying a city with laser vision]
Besides…like the creators of Godzilla won't need any more inspiration for their horror movies…