1. Chapter 10: Cell Growth and Division
Section 1: Cell Growth, Division, and Reproduction
Section 2: The Process of Cell Division
Section 3: Regulating the Cell Cycle
Section 4: Cell Differentiation

2. Cell Size Limitations Cells come in a wide variety of sizes and shapes
Why can’t most organisms be just one giant cell?
Information overload on DNA
Surface area to volume ratio
Diffusion limits cell size

3. Diffusion limit on cell size
Although diffusion is a fast and efficient process over short distances, it becomes slow and inefficient as the distances become larger.

4. Surface area-to-volume ratio
4 mm
4 mm
2 mm
2 mm
1 mm
1 mm
2 mm
4 mm
Surface area = 6 mm2 Volume = 1 mm3
Surface area = 24 mm2 Volume = 8 mm3
As a cell’s size increases, its volume increases much faster than its surface area
If cell size doubled, the cell would require eight times more nutrients and would have eight times more waste to excrete.
The surface area, however, would increase by a factor of only four.
The cell would either starve to death or be poisoned from the buildup of waste products.

5. THINK ABOUT IT Does cell division stop when you are finished growing?
What role does cell division play in your life?
Does cell division stop when you are finished growing?

6. Cell Reproduction
Cell division is the process by which new cells are produced from one cell
Results in two cells that are identical to the original

7. Chromosomes
What is the role of chromosomes in cell division?
Chromosomes make it possible to separate DNA precisely during cell division.

8. Chromosomes
The genetic information that is passed on from one generation of cells to the next is carried by chromosomes.
Every cell must copy its genetic information before cell division begins.
Each daughter cell gets its own copy of that genetic information.
Cells of every organism have a specific number of chromosomes.

9. Prokaryotic Chromosomes
Prokaryotic cells lack nuclei. Instead, their DNA molecules are found in the cytoplasm.
Most prokaryotes contain a single, circular DNA molecule, or chromosome, that contains most of the cell’s genetic information.

10. Eukaryotic Chromosomes
In eukaryotic cells, chromosomes are located in the nucleus, and are made up of chromatin.

11. Chromatin is composed of DNA and histone proteins.

12. DNA coils around histone proteins to form nucleosomes.

13. The nucleosomes interact with one another to form coils and supercoils that make up chromosomes.

14. The large, complex chromosomes of eukaryotes duplicate with each cell division
Chromosomes contain a very long DNA molecule with thousands of genes
Individual chromosomes are only visible during cell division
They are packaged as chromatin
Before a cell starts dividing, the chromosomes are duplicated
This process produces sister chromatids
Sister chromatids
Centromere

15. double-stranded human chromosomes
ready for mitosis

16. The Cell Cycle
What are the main events of the cell cycle?
During the cell cycle, a cell grows, prepares for division, and divides to form two daughter cells.

17. The Prokaryotic Cell Cycle
The prokaryotic cell cycle is a regular pattern of growth, DNA replication, and cell division.
Most prokaryotic cells begin to replicate, or copy, their DNA once they have grown to a certain size.
When DNA replication is complete, the cells divide through a process known as binary fission.

18. The Prokaryotic Cell Cycle
Binary fission is a form of asexual reproduction during which two genetically identical cells are produced.
For example, bacteria reproduce by binary fission.

19. The Eukaryotic Cell Cycle
The eukaryotic cell cycle consists of four phases: G1, S, G2, and M.
Interphase is the time between cell divisions. It is a period of growth that consists of the G1, S, and G2 phases. The M phase is the period of cell division.

21. G1 Phase: Cell Growth
In the G1 phase, cells increase in size and synthesize new proteins and organelles.

22. S Phase: DNA Replication
In the S (or synthesis) phase, new DNA is synthesized when the chromosomes are replicated.

23. G2 Phase: Preparing for Cell Division
In the G2 phase, many of the organelles and molecules required for cell division are produced.

24. M Phase: Cell Division
In eukaryotes, cell division occurs in two stages: mitosis and cytokinesis.
Mitosis is the division of the cell nucleus.
Cytokinesis is the division of the cytoplasm.

25. Getting from there to here…
Going from egg to baby….
the original fertilized egg has to divide…
and divide…

26. Why do cells divide… One-celled organisms Multi-celled organisms
for reproduction
asexual reproduction (clones)
Multi-celled organisms
for growth & development
from fertilized egg to adult
for repair & replacement
replace cells that die from normal wear & tear or from injury
amoeba
starfish

27. The Phases of mitosis
The four phases of mitosis are prophase, metaphase, anaphase, and telophase.
PMAT

28. Important Cell Structures Involved in Mitosis
Chromatid – each strand of a duplicated chromosome
Centromere – the area where each pair of chromatids is joined

29. Important Cell Structures Involved in Mitosis
Centrioles – tiny structures located in the cytoplasm of animal cells that help organize the spindle
Spindle – a fanlike microtubule structure that helps separate the chromatids

30. Prophase
During prophase, the first phase of mitosis, the duplicated chromosome condenses and becomes visible.

31. Prophase
The centrioles move to opposite sides of nucleus and help organize the spindle.

32. Prophase
The spindle forms and DNA strands attach at a point called their centromere.

33. Prophase
The nucleolus disappears and nuclear envelope breaks down.

34. Metaphase
During metaphase, the second phase of mitosis, the centromeres of the duplicated chromosomes line up across the center of the cell.

35. Metaphase
The spindle fibers connect the centromere of each chromosome to the two poles of the spindle.

36. Anaphase
During anaphase, the third phase of mitosis, the centromeres are pulled apart and the chromatids separate to become individual chromosomes.

37. Anaphase
The chromosomes separate into two groups near the poles of the spindle.

38. Telophase
During telophase, the fourth and final phase of mitosis, the chromosomes spread out into a tangle of chromatin.

39. Telophase
A nuclear envelope re-forms around each cluster of chromosomes.

40. Telophase
The spindle breaks apart, and a nucleolus becomes visible in each daughter nucleus.

41. Mitosis in whitefish blastula

42. Mitosis in plant cell

43. onion root tip

44. Cytokinesis How do daughter cells split apart after mitosis?
Cytokinesis completes the process of cell division – it splits one cell into two.

45. The process of cytokinesis is different in animal and plant cells.
Cytokinesis is the division of the cytoplasm.
The process of cytokinesis is different in animal and plant cells.

46. Cytokinesis in Animal Cells
The cell membrane is drawn in until the cytoplasm is pinched into two equal parts.
Each part contains its own nucleus and organelles.

47. Cytokinesis in Plant Cells
In plants, the cell membrane is not flexible enough to draw inward because of the rigid cell wall.
Instead, a cell plate forms between the divided nuclei that develops into cell membranes.
A cell wall then forms in between the two new membranes.

49. The Stages of the Cell Cycle

50. Mitosis
What events occur during each of the four phases of mitosis?
During prophase, the genetic material inside the nucleus condenses and the duplicated chromosomes become visible. Outside the nucleus, a spindle starts to form.

51. Mitosis
What events occur during each of the four phases of mitosis?
During metaphase, the centromeres of the duplicated chromosomes line up across the center of the cell. Spindle fibers connect the centromere of each chromosome to the two poles of the spindle.

52. Mitosis
What events occur during each of the four phases of mitosis?
During anaphase, the chromosomes separate and move along spindle fibers to opposite ends of the cell.

53. Mitosis
What events occur during each of the four phases of mitosis?
During telophase, the chromosomes, which were distinct and condensed, begin to spread out into a tangle of chromatin.