Why are cells so small?
 Take 3 blocks of agar of different size (1cm, 2cm, 3cm) → these are our cell models
 Measure the length, width and height of each cube using a ruler
 Calculate the area of each face of the cubes and add all the areas together for a single cube

 a cube has 6 faces → the total surface area is the same as the area of one side multiplied by 6
 Calculate the volume of each cube
 Report the surface areatovolume in the table below
Data Table: Calculating Surface AreatoVolume Ratio
Cell Model (cube) 
Length 
Width 
Height 
Total Surface Area 
Volume of cell 
Surface Area: Volume 
1 

2 

3 
Stop and think:
 Which cube has the greatest surface area:volume ratio?
 Which cube has the smallest surface area:volume ratio?
 Hypothesize: In an osmosis or diffusion experiment, which cube size would have the greatest diffusion rate?
Procedures:
 Each group will aquire three agar cubes: A 3cm cube, a 2cm cube, and a 1cm cube. CUT AS ACCURATELY AS POSSIBLE . (This may be already completed for you.)
 Place cubes into a beaker and submerge with 200 ml NaOH
 Let the cubes soak for approximately 10 minutes.
 Periodically, gently stir the solution, or turn the cubes over.
 After 10 minutes, remove the NaOH solution
 Blot the cubes with a paper towel.
 Promptly cut each cube in half and measure the depth to which the pink color has penetrated. Sketch each block’s crosssection.
 Record the volume that has remained white in color.
 Do the following calculations for each cube and complete the following data table:
Data Table: Calculation of Diffusion AreatoVolume
Cube Size 
Cube volume (cm^{ 3} ) V_{ total} 
Volume white (cm^{ 3} ) V_{ white} 
Sketch of each Cube 
Volume of the diffused cube ( V_{ total} – V_{white} ) V_{ diffused} 
Percent Diffusion (V_{ diffused} /V_{ total} ) 
Surface Area: Volume (from previous table) 
1cm  
2cm  
3cm 
Conclude:
 Which cube had the greatest percentage of diffusion?
 Did this meet your expectations with your hypothesis?
 If you designed a large cell, would it be a large sphere or something long and flat?