1. Cell Growth and Division
Chapter 10

2. Cell growth limiting factors
Limiting factors- conditions that prevent endless expansion.
Cell growth limiting factors
Diffusion
DNA content
Surface area-to-volume ratio
Cells range from 2 to 200 micrometers in diameter.

3. DNA Limits
DNA in the nucleus is the blueprint for all protein production in the cell.
DNA replicates protein blueprints very slowly. The larger the cell, the more protein needed.
The more protein needed the more DNA is required.
The nucleus can only contain a small amount of DNA. Larger cells contain multiple nuclei.

4. Diffusion Rate Limits Diffusion rate
Nutrients move about the cell primarily by passive transport.
Diffusion is very slow through cytoplasm.
It would take over one week to diffuse glucose across a 2cm stretch of cytoplasm!

5. Surface area-to-volume ratio Limits
As the cells surface area doubles its volume increases 8 times.
A cell with a surface area of 6 mm has a volume of 1 cubic mm. Double length of each side and the volume goes to 8 cubic mm.
In other words, you have a greater area for materials to diffuse throughout.

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

7. Solution to Limits Cell division
As a cells volume increases, the diffusion rate becomes too slow to carry essential nutrients to the organelles
and the DNA cannot replicate plans fast enough.
So the solution is Cell Division

8. Cell Cycle Every cell goes through a sequence of growth and division.
Two general periods
Growth
Division
Interphase- the longest period of a cell’s life cycle. Growth and metabolism take place in interphase.

9. Cell Cycle Interphase – 3 steps
G1 - “gap 1” - first growth phase; cell gets larger
S - “synthesis” - DNA is replicated and chromosomes are copied for division
G2 - “gap 2” - second growth phase; final preparation for division

10. Cell Cycle Cell Division Short period of time.
This is divided into phases.
The nucleus is divided during mitosis
The cytoplasm is divided last in cytokinesis

11. Figure 10–4 The Cell Cycle Section 10-2 G1 phase M phase S phase

12. Concept Map Cell Cycle Section 10-2 includes M phase (Mitosis)
Interphase
is divided into
is divided into
G1 phase
S phase
Prophase
G2 phase
Metaphase
Telophase
Anaphase

13. Interphase
There are three stages of interphase: G1
S stage G2

14. Interphase G1-stage Rapid growth.
Cells do the majority of growing during this phase.
Cells make new proteins and organelles during this phase.
Chromosomes not visible because they are loosely wound.

15. Interphase S-stage Occurs after the G1-phase
Chromosomes are replicated.
DNA is duplicated along with key proteins the chromosomes need.

16. Interphase G2-stage Occurs after S-phase is complete.
The shortest of three interphases.
Any organelles left to be duplicated are duplicated in this phase.

17. Figure 10–5 Mitosis and Cytokinesis
Section 10-2
Spindle forming
Centrioles
Chromatin
Centromere
Nuclear envelope
Centriole
Chromosomes (paired chromatids)
Interphase
Prophase
Spindle
Cytokinesis
Centriole
Metaphase
Telophase
Individual chromosomes
Anaphase
Nuclear envelope reforming

18. Cell Division
Consists of mitosis (period of nuclear division) and cytokinesis (division of the cytoplasm).
Two daughter cells are produced
each with a complete set of chromosomes.
4 stages of mitosis
Prophase
Metaphase
Anaphase
Telophase

19. Centromeres

20. Prophase Prophase is the 1st and longest stage of mitosis.
Characterized by the tightening up of the loosely wound chromatin into sister chromatids.
The disappearance of the nucleolus & nuclear membrane.
You find the appearance of centromeres and spindles.

21. Prophase Metaphase Early mitotic spindle Centrosome Centromere
Fragments of
nuclear envelope
Chromosome, consisting
of two sister chromatids
Spindle
microtubules
Spindle
Figure 8.7.2

22. Figure 10–5 Mitosis and Cytokinesis
Section 10-2
Spindle forming
Centrioles
Chromatin
Centromere
Nuclear envelope
Centriole
Chromosomes (paired chromatids)
Interphase
Prophase
Spindle
Cytokinesis
Centriole
Metaphase
Telophase
Individual chromosomes
Anaphase
Nuclear envelope reforming

23. Metaphase Metaphase is the 2nd stage in mitosis.
In this short phase the centromeres connect to the spindle fibers.
The chromosomes align themselves along the “equator” of the cell.

24. Figure 10–5 Mitosis and Cytokinesis
Section 10-2
Spindle forming
Centrioles
Chromatin
Centromere
Nuclear envelope
Centriole
Chromosomes (paired chromatids)
Interphase
Prophase
Spindle
Cytokinesis
Centriole
Metaphase
Telophase
Individual chromosomes
Anaphase
Nuclear envelope reforming

25. Anaphase Anaphase is the 3rd stage of mitosis.
In anaphase the chromosomes are split apart.
Each identical copy gets pulled toward the “poles” of the cell by the spindle fibers.

26. Figure 10–5 Mitosis and Cytokinesis
Section 10-2
Spindle forming
Centrioles
Chromatin
Centromere
Nuclear envelope
Centriole
Chromosomes (paired chromatids)
Interphase
Prophase
Spindle
Cytokinesis
Centriole
Metaphase
Telophase
Individual chromosomes
Anaphase
Nuclear envelope reforming

27. Telophase Telophase is the last stage of mitosis.
Most of the other characteristics of the previous stages are reversed.
Cell begins to divide.

28. Figure 10–5 Mitosis and Cytokinesis
Section 10-2
Spindle forming
Centrioles
Chromatin
Centromere
Nuclear envelope
Centriole
Chromosomes (paired chromatids)
Interphase
Prophase
Spindle
Cytokinesis
Centriole
Metaphase
Telophase
Individual chromosomes
Anaphase
Nuclear envelope reforming

29. Click the image to play the video segment.
Animal Cell Mitosis
Click the image to play the video segment.

30. Cytokinesis The division of cytoplasm.
Differs in plant & animal cells.
Animal cells simply pinch into two cells.
Plant cells lay down a cell plate at which point the cell divides.

31. Figure 10–5 Mitosis and Cytokinesis
Section 10-2
Spindle forming
Centrioles
Chromatin
Centromere
Nuclear envelope
Centriole
Chromosomes (paired chromatids)
Interphase
Prophase
Spindle
Cytokinesis
Centriole
Metaphase
Telophase
Individual chromosomes
Anaphase
Nuclear envelope reforming

32. Click the image to play the video segment.
Animal Cell Cytokinesis
Click the image to play the video segment.
Video 2

33. Cell Division Controls
You have many ways cell growth can be controlled.
External Regulators
Outside signals that tell the cell to divide.
I.e. a cut wound
Internal Regulators
Proteins that respond to signals inside cells that tell the cell to grow.
I.e. cyclins

34. Control of Cell Division
Section 10-3

35. Figure 10–8 Effect of Cyclins
Section 10-3
The sample is injected into a second cell in G2 of interphase.
A sample of cytoplasm is removed from a cell in mitosis.
As a result, the second cell enters mitosis.

36. What Is Cancer? What is cancer?
Cancer is caused by a breakdown in control of the cell cycle

37. Uncontrolled Cell growth
From time to time the cell growth regulators do not work.
This is essentially what cancer is.

38. Cancer cells divide excessively
Cancer cells spread from a malignant tumor
Metastasis is the spread of cancer
Lymph
vessels
Tumor
Glandular
tissue
Metastasis
A tumor grows from a
single cancer cell.
Cancer cells invade
neighboring tissue.
Cancer cells spread through lymph and blood vessels to other parts of the body
Figure 8.9

39. Cancer cells are often grown in culture for study
Figure 8.10

40. Cancer Treatment Cancer treatment
Radiation therapy disrupts cell division
Chemotherapy involves drugs that disrupt cell division