Cells regulate their size through a cell cycle of growth, DNA replication, and division. As cells grow larger, it becomes more difficult for them to exchange nutrients and waste due to a decreasing ratio of surface area to volume. The cell cycle is a series of phases that prepare the cell for division, including replicating DNA and organelles. Mitosis then divides the nucleus and cytoplasm, forming two daughter cells each with their own set of chromosomes. Strict regulation is needed to control when cells divide.

1. Cell Growth and Division Chapter 10

5. Surface Area vs. Volume Cell Size 5 cm 10 cm Surface Area (l×w×6) 150 cm 2 600 cm 2 Volume (l×w×h) 125 cm 3 1000 cm 3 SA to Volume Ratio 150/125 = 6:5 600/1000 = 6:10

8. Events of the Cell Cycle

11. Mitosis It is the division of the nucleus

14. Prophase

16. Metaphase

18. Anaphase

20. Telophase Two cells dividing into four

22. Which phases can you see? Prophase Metaphase Anaphase Telophase Interphase

24. Cellular Response to Injury

25. Effect of Cyclins Cytoplasm is removed from cell in mitosis Cytoplasm is injected into a second cell in G 2 phase Second cell enters mitosis