1. Chapter 8: Cell Growth and Division
8-2: Cell division: Mitosis and cytokinesis

2. Learning Objectives You should be able to:
Give two physical reasons why mitosis must occur.
Draw a chromosome and determine chromosome number.
Identify, draw, and describe each stage of the cell cycle.

3. Cell Growth Cells divide rather than get larger because…….
Demands on DNA would be too great.
Cell would have trouble moving food and waste across the cell membrane.

4. If a cell got too large, it would be more difficult to get oxygen in and waste products out.
Volume increases faster than surface area.

5. If a cell got too large, it would be more difficult to get oxygen in and waste products out.
Volume increases faster than surface area.

6. Approximate Time Required
If a cell got too large, it would be more difficult to get oxygen in and waste products out.
Distance of Diffusion
Approximate Time Required
10 nm
23.8 ns
50 nm
595 ns
100 nm
2.38 μs
1 μm
238 μs
10 μm
23.8 ms
100 μm
2.38 s
1 mm
3.97 min
1 cm
6.61 hours
10 cm
27.56 days
Diffusion is slow over long distances.

7. Chromosomes Each organism has a specific number of chromosomes.
During cell division, chromatin condenses into chromosomes.
In order for each cell to get the right number the chromosomes have to replicate

8. Parts of a chromosome
Chromatid: one copy of a newly copied chromosome; still joined to original chromosome by centromere

9. How to Draw a Chromosome
On whiteboard

10. Chromosomes: count centromeres!

11. Chromosomes: count centromeres!

12. Stop!
Please copy down Fig 8-10 in your notes before proceeding.

13. Outline of Today’s topics
Cell Cycle
Interphase
Cell Division
Mitosis
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis

14. The Cell Cycle
The series of events that cells go through as they grow and divide.

15. Interphase G1 – Growth phase #1.
Cells increase in size and make new proteins and organelles.
S – Synthesis.
Chromosomes are replicated.
G2 – Growth Phase #2
Cell division organelles are produced. Short phase.

16. Interphase During interphase, chromosomes in uncondensed form
“X” structure not visible

17. Outline of Today’s topics
Cell Cycle
Interphase
Cell Division
Mitosis
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis

18. Cell Division Why do cells divide? Growth, repair
Make identical copies of each other

19. Cell Division
Two Steps: 1. Mitosis – division of the nucleus. Divided into 4 phases. 2. Cytokinesis – division of the cytoplasm.

20. Outline of Today’s topics
Cell Cycle
Interphase
Cell Division
Mitosis
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis

21. Prophase Chromosomes condense (are visible) Centrioles separate
Spindle fibers form
Nuclear membrane breaks down.

22. Metaphase
Chromosomes line up in the middle of the cell

23. Anaphase
Chromosomes are pulled apart/away from each other.

24. Telophase The opposite of prophase occurs.
Chromosomes disappear back to chromatin
Nuclear membrane reforms
Spindle fibers break apart and disappear

25. Cytokinesis
Cytokinesis occurs right after Mitosis and is the division of the cytoplasm.
Result: two daughter cells!

26. Outline of Today’s topics
Cell Cycle
Interphase
Cell Division
Mitosis
Prophase
Metaphase
Anaphase
Telophase
Cytokinesis

27. Can you tell the phase?

29. Homework
Worksheet (on website: print out and complete, or simply write down answers)
Review stages of mitosis, or you will be confused next class!
Watch amoeba sisters video