10-1 Cell Growth Vocabulary: Cell Division Key Concept: What problems does growth cause for cells?

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

2 Reasons Why 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” It is hard to move enough food and wastes across the cell membrane into the cell!

Why Does the Rate of Exchange Become Difficult? How fast things move into or out of a cell (across the cell membrane) depends on SURFACE AREA   How quickly these materials are used by the cell depends upon the VOLUME of the cell

SURFACE AREA and VOLUME do NOT increase at the same rate and this is a problem for the cell! example: traffic increases as size of city increases (volume), but the roads stay the same (surface area) Result: TRAFFIC JAM!!!

(SA = Surface Area) ex: 1cm 2cm SA= length x width x # of sides   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)

the lower the SA/Volume ratio, the harder it is to get things the cell needs into or out of the cell  to solve the problem, the cell divides into 2 smaller cells (daughter cells)

This Process is Called… 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

What are two reasons why cell have to remain small?   What are two reasons why cell have to remain small?  

Which surface area to volume ratio is more favorable 6:1 or 3:1?   Which surface area to volume ratio is more favorable 6:1 or 3:1?