1. Objective: To understand SA:V ratio and why a cell needs to divide.

2. Why a cell divides Cell Growth: Grow by dividing instead growing larger The larger a cell is the more demand is put on DNA and nutrients can’t move through big cells easily

3. Why a cell divides DNA: Enough info. For a small cell, but if cell got too big there would be an info shortage Ex: small town library would not be useful to a big city

4. Why a cell divides Exchanging materials: Materials enter/leave by moving through the membrane The rate of exchange depends on how much surface area the rate of materials needed depends on volume.

5. Understand SA:V ratio Surface area: cell membrane (candy coating on M and M) Volume: cell contents (chocolate center in M and M) Surface area to volume ratio: Take the surface area (in cm 2 ) and divide by volume (in cm 3 )

6. Figuring SA:V If a side is 1 cm and there are 6 sides the SA would be 6*1cm 2 = 6 cm 2 V would be 1cm 3 = 1cm 3 SA:V= 6:1 or 6/1

7. Why a cell divides Volume increases more rapidly than Surface area, The SA:V decreases—this can cause serious problems To keep SA:V at a normal ratio: Cell DividesA Cell will form 2 daughter cells 1 st : cell copies DNA 2 nd: cell divides Now each daughter cell has an increased SA:V ratio