1. Chapter 10 Cell Growth & Division Section 10-1
Read 1st Paragraph
Fig. 10-1

2. Limits To Cell Growth
2 reasons why cells divide rather than get larger.
They don’t have enough DNA.
They can’t move enough nutrients & wastes across the cell membrane.

3. DNA “Overload” Remember:
DNA control’s cell function.
DNA is stored in the nucleus.
When a cell is small, the info in DNA is able to meet the cell’s needs.
But, as a cell increases in size, it doesn’t make more DNA.
If it were to keep growing, there would be an “Information Crisis”.

4. Cellular DNA

5. Compare the DNA in the nucleus to that of a small library.
Read P. 241
Middle paragraph

6. Exchanging Materials
Recall that food, H2O, & O2 pass through CM’s easily by passive & active transport.
Waste also leaves the cell through the cell membrane.

7. The rate at which these exchanges take place depends on the surface area of the cell.
Surface area =Total area of the cell membrane (CM).
However, the rate at which food & O2 are taken in, & wastes produced depends on the cell’s volume.
Volume =How much space is in the cell.

8. Surface Area –Volume Ratio
Imagine a cell shaped like a cube.
p. 243, fig Follow along!
Important things to note:
Volume increases much faster than surface area.
This causes the surface area-volume ratio to decrease.
This causes serious problems for the cell.

9. S.A. to Volume Ratio

10. Surface Area to Volume Ratio
Cell Size
Surface Area (length x width x 6)
Volume
(length x width x height)
Ratio of Surface Area to Volume

11. Use the street –traffic analogy.
Read p. 242, bottom paragraph.
If a cell got too big, it would have trouble getting enough O2 & nutrients in, & waste out.

12. Division of the Cell Before cells get too big they divide.
Division creates 2 “daughter cells”.
This is called cell division.
Before cell division occurs, the cell copies its DNA.
This solves the problem of info shortages.
Cell division also solves the volume problem.
By reducing size, the cell reduces volume.

13. Cell Division

14. Cell Division Section 10-2
Read p. 244 top paragraph
In prokaryotes (pro-k), cell division is just the splitting of the cell into 2 parts.
In eukaryotes (eu-k), cell division is complex & happens in 2 stages:
Mitosis
Cytokinesis

15. Prokaryotic Cell Division

16. Reproduction through mitosis is considered asexual.
All the cells are identical to the parent cell.
What are the resulting cells called?

17. Chromosomes In eukaryotes, genetic info is carried by chromosomes.
Chromosomes are made of DNA & proteins.
Every org. has a certain # of chromosomes:
Examples:
Roundworm = 2
Carrot cells = 18
Dolphin = 44
Human cells = 46
Chimpanzee = 48
Dog = 78
Hermit crab = 254

18. Chromosomes are normally visible only during cell division.
The rest of the time they are in a form known as chromatin.
Before cell division happens, chromosomes are copied.
For this reason, each chromosome consists of TWO identical “sister” chromatids. See p. 244, Fig. 10-3

21. When cells divide, the “sister” chromatids separate from each other.
1 chromatid goes to each of the 2 new cells.

22. Chromatids are held together by a centromere.
Normally the middle of the chromatid
Some can lie near the ends.
A human cell contains 46 chromosomes (sometimes referred to as 23 pairs)
Each consisting of 2 chromatids.

23. The Cell Cycle
Cell cycle –series of events that cells go through as they grow & divide.
Interphase –period b/t cell divisions.
During each cell cycle:
A cell grows
Prepares for division
Divides to form 2 daughter cells
p. 245, fig. 10-4

24. The Cell Cycle G1 Phase S Phase G2 Phase M Phase Consists of 4 phases:

25. Events of the Cell Cycle
Most of a cell’s life is spent in interphase.
Interphase is divided into 3 phases: G1
Cells do most of their growing.
New proteins & organelles are also made. S
Chromosomes are copied.
Synthesis of DNA molecules takes place. G2
Shortest of the 3 phases.
Organelles & molecules required for cell division are made.
When the G2 phase is done, the cell is ready to enter the M phase. a.k.a. = cell division

26. Mitosis Divided into 4 phases:
Prophase
Metaphase
Anaphase
Telophase
Depending on the cell, mitosis can last from minutes to days.
PMAT

27. Prophase 1st & longest phase. Chromosomes become visible.
Centrioles separate & take up positions on opposite sides of the nucleus.
Centrioles -2 tiny structures located near the nuclear envelope.

28. Spindle –a fanlike
Microtubule structure that helps separate chromosomes.
Plant cells don’t have centrioles.
Near the end of prophase:
Chromosomes coil more tightly.
The nucleolus disappears.
The nuclear envelope breaks down.

29. Metaphase 2nd phase Often lasts only a few minutes.
Chromosomes line up at the midline or equator of the cell.
The centromeres of each chromosome connect to the spindle.

30. Anaphase 3rd phase During anaphase:
The centromeres joining the sister chromatids, separate & become individual chromosomes.
These chromosomes then move to opposite ends of the cell called poles.
Anaphase ends when the chromosomes stop moving.

31. Telophase The 4th & final phase.
Chromosomes begin to disperse into a tangle of dense material.
The nuclear envelope
reforms around the
chromosomes.
The spindle breaks apart.
The nucleolus becomes
visible again.

33. Cell Cycle includes M phase (Mitosis) Interphase is divided into
G1 phase
S phase
Prophase
G2 phase
Metaphase
Telophase
Anaphase

34. Interphase
Prophase
Metaphase
Anaphase
Telophase

36. Cytokinesis Cytokinesis –the division of the cytoplasm.
Cytokinesis usually occurs at the same time as telophase.
It occurs in primarily 2 ways:
By pinching off b/t the 2 daughter cells equally.
Done in animal cells.
By building a cell plate b/t the 2 cells.
Done in plant cells.

38. Mitosis Video http://www.johnkyrk.com/mitosis.html

40. Regulating the Cell Cycle
Section 10-3
Regulating the Cell Cycle

41. Note! Ex: Not all cells move through the cell cycle at same rate.
Muscle cells & nerve cells don’t divide at all, once they are developed.
Skin cells, digestive cells, & cells in bone marrow that make blood cells, divide rapidly throughout our life.
Rapidly dividing cells can pass through a cell cycle every few hrs.

43. Controls of Cell Division fig.10-7
This illustration shows that cell division can be turned on & off.
The same thing happens when we have a cut in the skin or a broken bone.
New cells are made until the wound is healed, then they stop dividing.

44. Fig. 10-7
Cells in a petri dish will continue to grow until they come into contact w/ other cells.

45. Cell Cycle Regulators
In the 1980’s, scientists discovered what controls the cell cycle.
The substance was a protein called cyclin.
Cyclin regulates the cell cycle.
Since this discovery, scientists have found other proteins that are involved in the cell cycle.
They call all these proteins cyclins.
p. 251, fig. 10-8

46. Fig. 10-8 A sample of cytoplasm is removed from a cell in mitosis.
The sample is injected into a second cell in G2 of interphase.
As a result, the second cell enters mitosis.

47. There are 2 types of regulatory proteins:
Internal Regulators
External Regulators

48. Internal Regulators
Made up of proteins that respond to events inside the cell.
Allows the cell to only proceed when certain events have happened.
Ex:
Cells wont move to the next phase in mitosis until all the right steps have been completed.

49. External Regulators
Made up of proteins that respond to events outside the cell.
They direct cells to speed up or slow down the cell cycle.
Important during wound healing & embryonic development.

50. Uncontrolled Cell Division
Cancer –a disorder in which some of the body's own cells lose the ability to control growth.
Cancer cells don’t respond to the signals that regulate the growth of most cells.
As a result they divide uncontrollably & form masses of cells called tumors.
Tumors can damage surrounding tissues.
Cancer cells can also move throughout the body & cause serious problems, or even death.

51. Another cause is a damaged gene in a chromosome called the p53 gene.
What can cause cancer?
Tobacco
Smokeless or smoked
Radiation
X-ray UV
Radioactive
Viral infections
HPV-cervical cancer (inoculation available)
Another cause is a damaged gene in a chromosome called the p53 gene.
Damage to the p53 gene causes the cell to lose the info needed to respond to signals that would normally control their growth.

52. Cell Cycle Game http://www.pinterest.com/pin/245375879673392966/

53. Stem Cells