1. Cell Growth Cell Cycle Mitosis & Cytokinesis
Chapter 10

2. Limits to Cell Growth
The larger a cell becomes, the more demands the cell places on its DNA.
In addition, the cell has more trouble moving enough nutrients and wastes across the cell membrane.

3. Ratio of Surface Area to Volume
 As the size of a cell increases, its volume increases faster than the surface area.
The decrease in the cell’s ratio of surface area to volume makes it more difficult for the cell to move needed materials in and waste products out quickly enough for the cell to survive.

4. Ratio of Surface Area to Volume

5. Cell Cycle Micrograph

6. Events of the Cell Cycle
During the cell cycle, the cell grows, replicates its DNA, and divides into two daughter cells. DNA synthesis takes place during the S phase. Cell division takes place during the M phase. G1 and G2 are gap phases.

7. Cell Cycle
The cell cycle is the series of events that cells go through as they grow and divide.
Interphase is the period of growth that occurs between cell divisions.
90% of the cell’s time is spent here.

8. The Phases of the Cell Cycle
G1, S, G2= INTERPHASE
The cell cycle consists of four phases:
G1 (First Gap Phase)
S Phase (Synthesis Phase)
G2 (Second Gap Phase)
M Phase (cell division) Mitosis (Prophase, Metaphase,
Anaphase, Telophase) Cytokinesis (division on cytoplasm)

9. Events of the Cell Cycle
During G1 (First Gap phase) the cell
increases in size
synthesizes new proteins and organelles
During the S (Synthesis phase),
chromosomes are replicated or copied
DNA synthesis takes place
Once a cell enters the S phase, it usually completes the rest of the cell cycle.
During G2 Phase (Second Gap Phase)
Copying of certain organelles and molecules required for cell division occurs
Once G2 is complete, the cell is ready to start the M phase—Mitosis

10. Interphase “Intermission” Normal metabolic activities
Major state cell spends 90% of time here
DNA= chromatin
NOT a stage of mitosis

11. Late Interphase (S and G2)
Prepares for mitosis
DNA doubles=
Sister chromatids
Centrioles double in animals X X X X X X

12. Cell Division In eukaryotes, cell division occurs in two major stages.
The first stage, division of the cell nucleus, is called mitosis.
The second stage, division of the cell cytoplasm, is called cytokinesis.
FYI Some books will put cytokinesis as the last step of mitosis

13. Why do cells divide by Mitosis?
Growth &Repair
Reproduction of single celled organisms under conditions
Amobea
Reproducing

14. Cells dividing by Mitosis…….
Skin
Identical to original cell
Same chromosome #
Identical chromosome makeup

15. Duplicated Chromosome (After S phase of Interphase):X
Sister
Chromatids
Centromere

16. A Duplicated Chromosome
centromere
one chromatid
its sister
chromatid
One chromosome in the duplicated state

17. Diploid vs. Haploid Diploid= 2 sets of chromosomes
One set from mom and one set from dad
Chromosomes come in pairs
Humans have 23 pairs of chromosomes
Somatic Cells all cells except sperm and egg

18. Diploid vs. Haploid
Haploid = 1 set of chromosomes
Sperm or egg (sex cells) have 23 single chromosomes

19. Stages of Mitotic Cell Division
“1st” or “before”
“middle”
“apart”
“far” or separate
Prophase
Metaphase
Anaphase
Telophase

20. Stages of the cell cycle

21. Prophase Nuclear membrane disappears Doubled DNA = condensed
“chromosomes” form
Spindle fibers start to form
Prophase

22. Metaphase Mitotic spindle now formed
By centrioles in animals
Spindle apparatus in plants
Chromosomes line up mid- cell or center of cell

23. Anaphase Chromosomes move to opposite pole pulled by spindle fibers
Separate chromosomes

24. Spindle & spindle fibers: Pull apart the sister chromatids

25. Telophase Cell divides Cell plate (plants) or membranes (animals) form
Nucleus reappears (now 2 of them)
Chromosomes gather at opposite ends of the cell and lose their distinct shape.
Nuclear envelope reappears (now 2 of them)
Telophase

26. Cytokinesis:cell’s cytoplasm divides & splits apart

27. Plant versus Animal Mitosis
No cell wall
membrane cytokinesis = cleavage furrow
Centrioles
Plant:
Cell wall form
from cell plate Spindle apparatus

28. Cytokinesis in Plants Cell wall Cell plate
In plants, a structure known as the cell plate forms midway between the divided nuclei. This will become the spot where the cell walls will form
Cell wall
Cell plate

29. Cytokinesis in Animals
Cleavage furrow forms

30. Cancerous cells……... 1.Divide too many times
2.Divide into more than two cells!
Masses of cells =
“tumors”
benign
malignant

31. Onion Root Tip Micrographs of the Interphase and mitosis

32. Interphase

33. Prophase

34. Metaphase

35. Anaphase

36. Telophase

37. Identify the following

38. Identify the following

39. Identify the following

40. Identify the following

41. Identify the following

42. Identify the numbered cells5. 3 4 1. 2.

43. Identify the numbered cells6 7 8