1. Cell Growth and Division
Chapter 10

2. Why are cells so small? DNA Diffusion
Messages from the nucleus must be able to reach all parts of the cell
Diffusion
Nutrients must enter and wastes must leave
If the cell was too big, diffusion would happen too slowly

3. Limits to cell Growth
The larger the cell becomes the more demand it paces in its DNA. (DNA “overload)
The cell has more trouble moving enough nutrients and wastes across the cell membrane.(Exchanging Materials).

4. Why are cells so small? Surface Area vs. Volume
As a cell grows larger, the volume increases faster than the Surface Area (SA)
A bigger cell needs more nutrients, but has relatively less SA to take in those nutrients

5. Surface Area vs. Volume Cell Size 5 cm 10 cm Surface Area (l×w×6)
Volume (l×w×h)
125 cm3
1000 cm3
SA to Volume Ratio
150/125 = 6:5
600/1000 = 6:10

6. Cell Cycle
It is a series of events that cells go through as they grow and divide.

7. Events of the Cell Cycle
Cells divide before growing too large
Before dividing, cells must prepare
Preparation =Interphase=G1, S, G2 phase
G1 phase: Cell grows larger
S phase: Cell makes new DNA for daughter cell –DNA replication
G2 phase: Cell makes new organelles for daughter cell –preparation for mitosis

8. Events of the Cell Cycle

9. Chromosomes A DNA molecule & attached proteins
Centromere
Sister Chromatids
A DNA molecule & attached proteins
Each chromosome is replicated during the S phase
A replicated chromosome has two identical sister chromatids connected by a centromere

10. Chromosome A DNA molecule & attached proteins
Duplicated in preparation for mitosis
one chromosome (unduplicated)
one chromosome (duplicated)

11. Mitosis
It is the division of the nucleus

12. Mitosis Four Stages: Prophase (pro- means first)
Metaphase (meta- means middle/after)
Anaphase (ana- means apart)
Telophase (telo- means far away/end)

13. Prophase Chromatin condenses into chromosomes
condensing
Chromatin condenses into chromosomes
Nuclear envelope and nucleolus disintegrate
Centrioles migrate to opposite ends of the cell
Spindle fibers form in foot ball shape across cell

14. Prophase

15. Metaphase Chromosomes line up in the middle (equator) of the cell
Spindle fibers attach to centromeres

16. Metaphase

17. Anaphase Sister chromatids separate
Spindle fibers shorten, pulling chromatids to opposite ends of cell
Animal cells begin to pinch in
Plant cells begin to form cell plate in the middle

18. Anaphase

19. Telophase
Nuclear membrane built from ER around each set of chromosomes
Nucleolus reforms in each nucleus
Chromosomes become mass of chromatin

20. Two cells dividing into four
Telophase
Two cells dividing into four

21. Cytokinesis
Final division of cytoplasm (CM) resulting in two daughter cells
Animals – CM pinches together
Plants – Cell plate forms new CM dividing the daughter cells

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

23. Regulating the cell cycle Knowing when to divide
Cyclins
Protein that regulates the cell cycle in eukaryotes
Internal regulators – tell the cell when to enter mitosis
External regulators – control the rate of the cell cycle

24. Cellular Response to Injury

25. Effect of Cyclins Cytoplasm is injected into a second cell in G2 phase
Cytoplasm is removed from cell in mitosis
Second cell enters mitosis

26. Cancer
Cancer results when cells do not respond to cell cycle regulators
Cells grow unregulated, forming a tumor
Tumor damages surrounding tissue

27. Web activities http://www.millerandlevine.com/intro.html
(stem cell activities)