1. Chapter 8: Cell Growth and Division

2. Cell Growth Describe cell growth Define cell division Relate cell growth to cell division

3. Why do cells divide?  To reproduce  To grow bigger  To repair injuries  To become more efficient

4. Limits of Cell Growth 1.Volume grows faster than surface area 2.Therefore a larger cell has a more difficult time getting stuff into (oxygen & nutrients) and out of (wastes) the cell 3.SOLUTION: Cell Division

5. Rates of Cell Growth 1. Vary depending on cell type 2. E. Coli divide every 30 minutes 3. Some cells take much longer to divide or “stop” dividing for a while

6. Controls on Cell Growth 1.Some cells rarely/never divide – nervous and heart cells 2.Some cells divide daily – skin and digestive tract cells 3.STOP switch: cells stop growing when they bump into each other 4.ON switch: cut or break in tissue cause cells to grow rapidly (but growth slows as healing reaches completion)

7. Cell Division: Mitosis & Cytokinesis Define mitosis and cytokinesis Describe the cell cycle and the changes that take place during interphase Discuss the events and significance of mitosis

8. Chromosomes 1.Chromosomes: o“colored body” oseen only when the cell divides ocontain genetic info in the form of DNA oare coiled chromatin 2.Composition of Chromatin oMake up chromosomes oComposed of DNA and protein called histones (helps to condense the DNA) oDNA in a chromosome is 10,000x longer than the chromosome itself oMust condense in order to separate correctly during mitosis

9. oCan only see chromosomes during division oEach chromosome replicates and is paired as sister chromatids joined at a centromere oHuman cell = 46 chromosomes (2n)  “n” number = 23 = “haploid”  2n = 46 = “diploid”  4n = 92 (during interphase)  Body cells (aka somatic cells) = 2n = 46  Sex cells (aka eggs & sperm) = n = 23 Chromosome Structure

10. The Cell Cycle 1.Growth, prepares for division, divides (anywhere from 6 hours to 100 days) 2.3 Parts oInterphase oMitosis (PMAT) - few minutes to several days oCytokinesis

11. Interphase – 3 stages  More than 90% of the life of a cell is spent in this phase  G1: cell growth, development, and protein production (longest)  S: “Synthesis”, DNA replication  G2: Organelles replicated (shortest)  Note: DNA exists as chromatin (no chromosomes yet)

12. Mitosis - Prophase  Longest phase of MITOSIS (50- 60 % of total time required for mitosis)  Nuclear membrane starts to disintegrate  Chromosomes condense (become visible) – seen as 2 identical chromatids lying side by side held together by centromeres  Centrioles move to opposite poles  Spindle fibers grow from centrioles, attach at centromeres

13. Mitosis – Metaphase (hint “m”=middle)  Chromosomes attach to the spindle fibers  Chromosomes line up in the middle (aka equator)  Spindle fibers run from centrosomes to centromeres of the chromosomes

14. Mitosis - Anaphase (hint “a” = away)  Centromeres split  Spindles retract and pull sister chromatids apart  Chromosomes move to opposite poles (toward centrioles)

15. Mitosis - Telophase  Chromosomes cluster at poles  Chromosomes uncoil – back into chromatin  Nuclear envelope reforms around each new nuclei  Mitosis is done  Cell membrane begins to pinch in the middle

16. Cytokinesis Cell membrane moves inward and pinches in the middle forming two identical cells In plant cells – a cell plate (eventually becomes the cell wall) and cell membrane appear separating the 2 new cells There are now 2 identical cells – same DNA, etc.

17. http://media.pearsoncmg.com/bc/bc_camp bell_concepts_5/media/assets/interactive media/activityshared/ActivityLoader.html?c 6e&12&03&8B%20Mitosis%20and%20Cyt okinesis%20Animation http://media.pearsoncmg.com/bc/bc_camp bell_concepts_5/media/assets/interactive media/activityshared/ActivityLoader.html?c 6e&12&03&8B%20Mitosis%20and%20Cyt okinesis%20Animation http://media.pearsoncmg.com/bc/bc_camp bell_concepts_5/media/assets/videos/Ani malMitosis-V.html http://media.pearsoncmg.com/bc/bc_camp bell_concepts_5/media/assets/videos/Ani malMitosis-V.html

18. Pop Quiz???? 1.What is the main goal of cell division? 2.What are the 3 phases of interphase? 3.What are the 4 phases of mitosis? 4.A cell has 12 chromosomes. At the end of cell division how many cells will there be? 5.A cell has 12 chromosomes. At the end of cell division how many chromosomes will be in each cell?