1. Animal Cells and Plant Cells
Animal cells are usually circular in structure.
Plant cells are usually square in structure.

2. Cell Math
We can calculate surface area, volume and the surface area-to-volume ratio of different kinds of cells.
WE WILL BE DOING MATH. TAKE A DEEP BREATH AND RELAX. ITS NOT THAT BAD 

3. Plant Cells Remember plant cells are usually squares.
Surface area of a square = height X width X number of sides
Volume of squares = height X width X length
Surface-to-Volume ratio = S.A. / V

4. Animal Cells Remember animals cells are usually circular or SPHERES
Volume of spheres = 4/3 п r^3
Surface Area = 4 п r^2
Surface-to-Volume ratio = S.A. / V
П = 3.14
r = the radius of the sphere
d = diameter (2 X r)

5. Bacterial Cells
Bacterial cells replicate by a process called binary fission
Binary fission is when a cell divides and produces one exact copy of the other cell.
Bacterial cells divide constantly, sometimes at extremely fast rates

6. Bacterial Cell Replications
2^number of generations x initial number of bacteria = total # of bacteria present after n generations

7. Bacterial Cell (Cont.)
Example: Bacillus cereus divides every 30 minutes. You inoculate a culture with exactly 100 bacterial cells. After 3 hours, how many bacteria are present?
In 3 hours, B. cereus will divide 6 times. Therefore, n = ^6 = 64
100 x 64 = 6,400 cells

8. Why is this important?
The smaller the cell, the higher the surface area-to-volume ratio. The larger the cell, the smaller the ratio.
A high surface area-to-volume ratio helps facilitate the exchange of materials between a cell and it’s environment.
The higher the ratio, the greater contact a cell has with it’s environment.
The larger the cell, the longer the diffusion process would take.

9. Why is this important?
As the cell doubles in radius (more volume), the surface area is decreased by half.
Each unit of volume of cytoplasm within the cell has only half of the membrane area available to exchange nutrients and waste.
This helps to explain why cells are microscopic.
Larger organisms do not have larger cells than smaller organisms, they just have more cells.