1. The Eukaryotic Cell Cycle
Essential Question: What are the main events of the cell cycle and how does the cell grow and reproduce?

2. How does cell size affect how efficiently materials get to all parts of a cell?

3. How much longer would it take nutrients to get to the center of the larger cell compared to the smaller cell?

4. 4 Reasons why cells divide
1. Efficiency As cell grows bigger demand for transport across membrane is too great

5. 4 Reasons why cells divide
2. DNA Overload As cell grows bigger, DNA can’t send out instructions fast enough to instruct organelles on work to do

6. 4 Reasons why cells divide
3) Growth
4) Cells divide to replace worn out or damaged cells

7. Cell Division in Prokaryotes
Called Binary Fission
DNA is copied then cell divides

8. Cell Division in Eukaryotes
Called Mitosis
Cell Grows & Copies its DNA before it can divide

9. The series of events that cells go through as they grow & divide ~ The Cell Cycle
G0 phase: resting phase

10. 2 Phases of the Cell Cycle
Interphase
“M” Phase
Includes Mitosis & Cytokinesis

11. The Cell Cycle: G1 S G2 Prophase Metaphase Anaphase Telophase
Interphase
Mitosis

12. Interphase: a growth period
G1 (Growth/Gap 1) - Cell grows in size, makes new organelles & performs assigned function; DNA is relaxed in chromatin and is not visible
S phase (Synthesis) - duplicates DNA to prepare for mitosis
G2 (Growth/Gap 2) – cell prepares for mitosis

13. Talk to a partner: Explain the phases of Interphase

15. Mitosis occurs in 4 phases
Prophase
Metaphase
Anaphase
Telophase

16. Vocab Terms
Chromatin DNA “scrunched up” in the nucleus & is not visible
Chromosomecell structure that carries the genetic material
Sister chromatidsidentical halves of the duplicated parent chromosome
Centromerecell structure that joins the two sister chromatids of a chromosome

17. Prophase DNA organizes Nuclear membrane & nucleolus disappear.
chromatin condense into visible chromosomes.
Chromosomes are paired with their identical copies and are called sister chromatids.
Sister chromatids are held together as a pair by a centromere.
Nuclear membrane & nucleolus disappear.
Spindle fibers form between the pairs of centrioles, which have moved to opposite ends of the cell
Prophase

19. Metaphase Chromosomes line up in the middle of the cell.
Each chromatid is attached to a separate spindle fiber by its centromere.

21. Anaphase
Sister chromatids are pulled apart to opposite poles of the cell.

23. Telophase 2 identical daughter cells are formed.
Cytokinesis occurs (the division of the cytoplasm) as the plasma membrane pinches in along the equator.
Nucleolus and nuclear membrane reappear, chromosomes begin to uncoil & relax back into chromatin

25. Picture of cytokinesis
*Image courtesy Indigo Instruments. Visit indigo.com for more original content like this. Reprint permission is granted with this footer included.*

26. In plants…
Because plant cells have a cell wall, the plasma membrane does not pinch in.
Rather a structure known as the cell plate forms across the cell’s equator.

27. Plant in cytokinesis
It’s hard to see, but there is a cell plate forming in the middle of the cell, next to the arrow.

28. Finally…
After mitosis is complete, each new daughter cell is an identical copy of the parent cell. Both cells enter interphase to carry out their assigned function until they are ready to divide.

29. All together now…

30. Talk to a partner: Explain the phases of Mitosis

31. Cell Cycle practice

32. Cell Cycle Video Lingering Questions….
How long does the cell spend in each phase?
How does the cell know when it is ready to proceed to the next phase?
What happens when the cell is NOT growing or dividing?
What is the life span of human cells?
Does the cell continue in the cell cycle indefinitely?

33. How long does the cell spend in each phase?

34. How long does the cell spend in each phase?

35. How does the cell know when it is ready to proceed to the next phase
How does the cell know when it is ready to proceed to the next phase? Checkpoint control system
cell cycle controlled by STOP & GO chemical signals at critical points
signals indicate if key cellular processes have been completed correctly

36. 3 major checkpoints:

37. Checkpoint control system
3 major checkpoints:
G1 checkpoint
can DNA synthesis begin?
G2 checkpoint
has DNA been copied correctly?
commitment to mitosis
M checkpoint
AKA spindle checkpoint
Are chromosomes attaches to spindle properly allowing for sister chromatids to separate correctly?

38. Apoptosis
Programmed cell death
“Cell suicide”

39. What happens when the cell is not growing or dividing?
Cell is resting

40. When cells are damaged and need repair or need to be replaced, cell will reenter the cell cycle

41. What is the life span of human cells?

42. Explain why spinal cord injuries are irreversible
Think-Pair-Share: Explain why damage to heart muscle cells are permanent
Explain why spinal cord injuries are irreversible

43. Talk to a Partner: Do Cells Grow Indefinitely?
Section 10-3
If center cells are removed, cells near the space will start to grow again.
SHOWS: Cell division
genes can be turned on
and off
Cells grow until they touch other cells

44. Controlling Cell Growth Through Cell Signals (Gene Regulation)
Cell division stops when cells touch
Can resume if space is available (injury)
Cell division stops when they cannot absorb enough nutrients

45. What happens when the cell signal genes that control cell division become damaged?
Some cells do not respond to the signals that regulate the growth
Result ~ uncontrolled cell growth: cancer
Causes of cancer:
cigarette & tobacco use
radiation exposure (X-ray & UV light)
genetics
some viruses

46. Cell Cycle Regulation Genes
Cyclin Kinases
Cyclin Dependent Kinases
Tumor Suppressor Genes

47. Cyclin & Cyclin dependent kinases
Stimulates cell growth & drives the cell from one phase to next in cell cycle
CDK and cyclin together form an enzyme that activates other proteins by chemical modification (phosphorylation). The amount of CDK molecules is constant during the cell cycle, but their activities vary because of the regulatory function of the cyclins. CDK can be compared with an engine and cyclin with a gear box controlling whether the engine will run in the idling state or drive the cell forward in the cell cycle.

48. EX: Proto-oncogenes
when switched “on” accelerates cell cycle into overdrive (cells bypass G0)

49. Tumor Suppressor Genes
Inhibits Cell Division

51. Cancer Video

52. Stem Cells Stem cells - unspecialized cells
Through cell differentiation – stem cells become specialized in structure and function
Two Types: Embryonic and Adult Stem Cells

54. Cornell Summary