1. Chapter 9 Cellular Reproduction
9.1 Cellular Growth

2. Cells Come in Different Sizes
Red Blood Cell 8 um in diameter
Nerve Cell 1 m in length with very small diameter
Yolk of ostrich egg 8 cm
Most cells are um
1000 um = 1 mm

3. Limits to Cell Size
Diffusion
DNA
Surface to volume ratio

4. Diffusion Limits Cell Size
Within the cell nutrients must diffuse to all parts
Diffusion is based on random movement of particles
Diffusion is too slow for a large cell
When cells reach maximum size they die or divide

5. DNA Limits Cell Size
DNA contains all the instructions for synthesizing proteins (including enzymes)
Large cells would need more proteins
More copies of the DNA instructions would be needed for a large cell
Most cells contain only one set of DNA

6. Surface Area to Volume Ratio Limits Cell Size
As the size of a cell increases the volume increases faster than the surface area
If the cell size is doubled then need eight times more nutrients but plasma membrane is only four times larger
Cells divide before they become too large to function properly

7. Volume Increases Faster than Surface Area
What are the surface area to volume ratios?

8. The Cell Cycle Sequence of growth and division of a cell
Two main periods
Growth also called interphase
Division also called mitosis and cytokinesis

9. Cell Cycle

10. Interphase
NOT part of mitosis, rather the time between one mitosis and the next
Stages of interphase
G1 phase: rapid growth and metabolic activity
S phase: synthesis of DNA (additional copy is made)
G2 phase: centrioles and other organelles replicate; cell prepares for division

11. Chromosomes and Chromatin
Both are DNA
Chromosomes are the condensed form of DNA that is visible as individual strands.
Chromatin is the “relaxed” very thin form of DNA that is not visible as individual strands.
During interphase DNA is in the chromatin form.

12. Chromosomes and Chromatin
Chromatin DNA form
Chromosome DNA form
Chromatin DNA form

14. Cell Reproduction
Process of producing new cells from preexisting cells
Three Types
Fission: bacteria
Meiosis: sex cells
Mitosis: body cells
Needed for growth
Needed for repair

15. Bacteria Reproduce by Fission
Prokaryotes do not have a nucleus
They divide the cell contents then divide

16. Chapter 9 Cellular Reproduction
9.2 Mitosis and Cytokinesis

17. Eukaryote Cell Reproduction is Mitosis and Cytokinesis
Mitosis is division of the nucleus producing two genetically identical daughter cells from one parent cells
Needed for growth
Needed for repair
Cytokinesis is division of the cell contents
Usually they happen simultaneously

18. Phases of Mitosis
Prophase
Metaphase
Anaphase
Telophase

19. Chromosome Structure
Chromosome is two sister chromatids connected by a centromere
Chromosomes are made of DNA and contain genes (hereditary units)
Chromosomes are the condensed form of chromatin

20. Prophase Chromatin coils into visible chromosomes
Nuclear membrane disintegrates
Nucleus disappears
Centrioles migrate to opposite ends of cell
Spindle fibers form

21. Prophase

22. Metaphase Much shorter amount of time than prophase
Spindle fibers attach to centromere
Chromatids line up at the cell’s equator

23. Metaphase

24. Anaphase Centromeres split
Spindle fibers shorten to pull chromatids to each end of cell
Sister chromatids separate

25. Anaphase

26. Telophase Starts when chromatids get to opposite poles
Chromosome uncoil and become chromatin
Spindles breakdown
Nuclear membrane reforms
Nucleus becomes visible

27. Telophase

28. Cytokinesis Division of the cytoplasm
Plants form a cell plate, the beginning of a cell wall
Animals have cleavage furrow where the plasma membrane pinches in

29. Animal and Plant Cytokinesis

30. Results of Mitosis
Mitosis allows for genetic continuity in each generation of daughter cells
Same chromosomes
Same genes
Same exact DNA

31. Levels of Organization
In unicellular organisms one organism undergoes mitosis to make two organisms
In multicellular organisms one cell undergoes mitosis to make two cells that form tissues
Tissues of different types functioning together form organs
Organs functioning together form systems
Systems functioning together form organisms

32. Chapter 9 Cellular Reproduction
9.3 Cell Cycle Regulation

34. Length of Cell Cycle
Each cell type has a specific growth and reproduction time table
Frog embryo cell cycle of less than one hour
Cells lining your intestine hours
Mature nerve cells do not divide

35. Normal Control of the Cell Cycle
Much that science does not fully understand
Enzymes control the cell cycle
Many enzymes needed
Most enzymes are used at just one point in the cycle
Loss of a functional enzyme can cause the cell cycle to be “out of control”

36. Normal Control of the Cell Cycle
Signaling molecules made of a cyclin bound to a CDK kick off the cell cycle and drive it through mitosis.
Checkpoints monitor the cell cycle for errors and can stop the cycle if an error occurs
CDK are enzymes, cyclins are proteins

37. Genes and Proteins
Genes located on DNA are responsible for giving direction about what proteins (enzymes) to produce
A defective gene would produce a faculty enzyme that would not function correctly

38. Key Time for Control of the Cell Cycle
Key control of the cell cycle is just prior to S phase during interphase
If new DNA is synthesized then the cell will continue on with mitosis

39. Cancer A cell “out of control” of the cell cycle
Mistake in the Cell Cycle
Too fast rate of mitosis
Result of changes in one or more genes that produce enzymes that are involved in controlling the cell cycle

40. Cancer Cells

41. Cancer Cells Cancer cells form tumors
Tumors are masses of cells that interfere with normal functioning
Metastasis: cancer cells break off the tumor and travel to other locations to form tumors

42. Causes of Cancer Both genetic and environmental
When people move from one country to another their rate of cancer is that of the country they are now living
Example: Rate of breast cancer is high in US and low in Japan; when people move from Japan to US their rate of breast cancer increases

43. Environmental Causes of Cancer
Smoking
UV Light
Diet
Air Pollution

44. Environmental Causes of Cancer
Viruses
Cervical Cancer
Water Pollution

45. Cancer Prevention
Clear link between healthy lifestyles and incidence of cancer
Low fat, high fiber diet reduces risk
Daily exercise reduces risk
No tobacco in any form reduces risk

46. Apoptosis Programmed cell death
All animal cells have a “death program”
Fetal human tail cells have undergone apoptosis; programmed cell death at the appropriate time
Plant leaves undergo apoptosis in autumn when the leaves are falling
Apoptosis can help protect organisms from developing cancerous growths.

47. Stem Cells
Stem cells are unspecialized cells that can develop into specialized cells under the right conditions

48. Embryonic Stem Cells
After a sperm fertilizes an egg the cell divides until there is cells
Each of these cells can develop into a wide variety of specialized cells
Much controversy exists due to the ethical concerns about the source of these embryonic stem cells

49. Adult Stem Cells
Present in adults (and newborns) to produce the same type of cell
Not pluripotent (can’t become any cell type)
In 2000 adult stem cells ere used to restore lost brain tissue in mice
Less controversy exists to the use of adult stem cells