1. SA/Vol Ratio/Why are cells so small?

2. Why are cells so small?

3. Diffusion!
Cells need to be able to get materials around the cell in a efficient manner. They need to be small so they have lots of surface area and not much volume.
As cells get smaller their surface area to volume ratio gets bigger. This is exactly what cells need! That means that they have a lot of surface area (on the outside) to absorb things while they have limited volume (on the inside) for things to diffuse across!
Answer

4. Surface Area Equation Cube Rectangle SA = Width x Height x 6
SA = 2(L)(W) + 2(L)(H) + 2(W)(H)
Surface Area Equation

5. Volume = L x W x H
Volume Equation

6. Ratio = SA/Vol
SA/Vol Ratio

7. Examples Pick any length cube/rectangle and practice.
You can just choose random numbers.
L=26 cm
W=12 cm
H= 20 cm Or
L=6 cm
W=2 cm
H= 1 cm
You can pick any random numbers and practice!
The smaller the cube or rectangle gets the bigger the ratio gets, try it!!!
Examples