1. What problems does size and growth cause for cells?
Cell Growth
What problems does size and growth cause for cells?

2. When a Living Thing Grows…
On average, the cells of an adult animal are the same size as those of a young animal
The difference is that there are a lot more cells in an adult animal

3. Why does a Cell Divides Rather Than Continue to Grow Bigger?
More demands placed on the cell’s DNA
Ex: a small town library has enough books for people to borrow but if a lot of people move into the town, some people may have to wait for popular books; DNA is like a “genetic library”
More trouble moving enough nutrients & wastes across the cell membrane

4. Why Does the Rate of Exchange Become Difficult?
the rate of exchange for food, H2O, and oxygen across a cell's membrane depends upon the cell’s SURFACE AREA
how quickly these materials are used by the cell depends upon the VOLUME of the cell

5. SURFACE AREA & VOLUME DO NOT INCREASE AT THE SAME RATE & THIS IS A PROBLEM FOR THE CELL!
example: traffic increases as size of city increases, but the roads stay the same

6. ex: 1cm 2cm SA= length x width x # of sides SA= 6cm2 SA= 24cm2 Volume= 1cm3 Volume= 8cm3 SA/Volume ratio= 6:1 SA/Volume ratio= 3:1
(SA = Surface Area)

7. the lower the SA/Volume ratio, the harder it is to get materials into/out of the cell
 to solve the problem, the cell divides into 2 smaller cells (daughter cells)
ex: 1 E. Coli bacteria doubles in 30 minutes; at the end of 1day = 14kg of E. Coli!!
**in 3 days= mass of the Earth!!!!!

8. Cell Division
The process by which a cell divides into 2 daughter cells
Cell replicates (copies) all of its DNA
each cell will get a copy of the DNA
Solves DNA problem as well as reducing the cells volume so that materials can exchange across the membrane