1. Cell Growth and Division
Cell Cycle
Cell Growth and Division

2. 2. Why do cells divide? If the cell is too big:
Too much demand is placed DNA
Harder to move enough nutrients and wastes across the cell membrane

3. Surface area vs. volume

4. 4. Surface Area vs. Volume
As a cell increases in size, volume increases faster than surface area
This causes the ratio of surface area to volume to decrease.
This is a serious problem for the cell and is why the cell cannot grow any larger than it does.

5. 5. Cell division solves those problems
Before a cell becomes too large, a growing cell replicates its DNA and then divides into two new “daughter” cells. This is called mitosis.

6. Cell Cycle http://www.cellsalive.com/mitosis.htm

7. Main Events of a Cell Cycle
Interphase
G1, S G2
M Phase
Prophase
Metaphase
Anaphase
Telophase

8. Interphase The cell grows and replicates its DNA
Chromosomes are not visible, only chromatin

9. Prophase Chromatin condenses into chromosomes Centrioles separate
Nuclear envelope breaks down

10. Metaphase
Chromosomes line up across the center of the cell

11. Anaphase
Chromosomes are pulled apart by spindle into individual chromatids

12. Telophase Chromosomes gather at opposite ends of the cell
Two new nuclear envelopes form

13. Cytokinesis The cytoplasm pinches in half Plants lay down a cell plate
Cytokinesis
The cytoplasm pinches in half
Plants lay down a cell plate
Two new cells now exist.

14. Label the stages #7

15. What stops cell from growing?
Proximity to neighbor cells.
Cells in a petri dish will continue to grow until they come into contact with other cells.
Similarily, skin around a wound.

16. Which chemicals regulate the cell cycle?

17. How do cells respond to contact with other cells?

18. How are cancer cells different from other cells?