Chapter 10: Cell Growth and Division (pages 232- 251)

1. Chapter 10: Cell Growth and Division(pages 232- 251) Mr. Bragg 2012-2013

2. 10.1 Why do cells divide? • Explain the problems that growth causes for cells. • Compare asexual and sexual reproduction.

3. I. 10.1 Cell Growth, Division, and Reproduction • Limits to cell size • 2 main factors • The larger the cell becomes, the more the demands the cell has on its DNA • Larger cells have more trouble in moving enough food in and waste out

4. 2. Factor 1- “Information overload” • Cell’s DNA cannot keep up with the need for information b. Analogy: growing town and excess demands on town library • Over time the library would not be able to meet the needs of the town • Analogy #2- computer that runs too many processes

5. 3. Factor 2- Exchanging materials • Materials are moved in and out of the cell’s membrane • The larger a cell becomes, the more nutrients it needs and the more waste it produces • As a cell grows, the membrane cannot grow as fast as the volume.

6. Ratio of surface area to volume changes • Cube analogy: picture a cube with sides that measure 1cm in length, surface area to volume is 6:1 • Increase the length to 3cm and the ratio becomes 54/27 or 2:1 = gets smaller • The membrane (surface area) is not keeping pace with the growth of the volume 2nd analogy- water balloon!!!

7. d. “Traffic problems”- town analogy • 2 lane street • As the town grows more people use the street • The increase in traffic means it takes longer to get in/out of town • A cell that continues to grow would have the same problem

8. B. Cell Division and Reproduction • Before a cell gets too large, it divides creating “daughter cells” • Cell division- the process by which a cell divides into two new cells Daughter cells Original cell

9. 3. Benefits of cell division a. Each daughter cell gets its own copy of DNA b. Decreases cells volume c. Can result in reproduction

10. 4. Asexual reproduction- a process by which a single parent reproduces by itself a. This is how some multicellular and many unicellular organisms reproduce b. Offspring have the same genetic information as the parent Budding yeast cell

11. c. Examples: Budding hydra; bacterial cells, stick insects, many plants

12. 5. Sexual reproduction- a process by which two cells from different parents fuse, or join together, to produce the first cell of a new organism Marsupial tree frog (Gastrotheca cornuta)

13. Each cell comes from a different parent • Offspring have genetic information from both parents • Example: most animals and plants

14. 6. Advantages of asexual reproduction • Asexual- • Quick • Requires less energy • Produces clones • Good for organisms that are well suited for their environment • Non-motile organisms have difficulty finding mates • If the environment is particularly harsh, the more delicate or susceptible organs or stages of sexual reproduction may not be able to survive • When colonizing a new area, finding a mate for sexual reproduction may be difficult or impossible

15. 7. Advantages of Sexual reproduction

16. 7. Disadvantages • b. Sexual- • slower • Takes two parents • Asexual- • Lack of genetic diversity • Difficult to adapt to new conditions

17. 10.1 Why do cells divide? • Explain the problems that growth causes for cells. • Compare asexual and sexual reproduction.

18. 10.2 When do cells divide? • Describe the role of chromosomes in cell division. • Name the main events of the cell cycle.

19. II. 10.2 The Process of Cell Division • Chromosomes • DNA is a very large molecule a. Can be packaged into chromosomes b. Chromosomes- a threadlike structure that contains genetic information that is passed from one generation of cells to the next

20. 2. Prokaryotic chromosomes • Bacteria do not have a nucleus • DNA is found in the cytoplasm • The DNA is usually found in a single circular shaped chromosome

21. 3. Eukaryotic chromosomes • DNA is found in the nucleus • Have much more DNA than prokaryotes • DNA is packaged into chromosomes • Human body cells have 46 chromosomes

22. Nucleosome Game Rules: 1. Need to hop on one foot 2. Must get from point A to B without dropping yarn; otherwise, back to start 3. Can only use one pencil to transport 4. No tying, tape, or glue 5. Once in transport, yarn cannot move

23. e. Chromatin- the substance found in eukaryotic chromosomes that consists of DNA tightly coiled around histones • When cells are ready to divide the chromatin condenses and individual chromosomes can be seen inside the cell Factoid: Each human cell has about 1.8 meters of DNA, but wound on the histones it has about 90 millimeters of chromatin. DNA Packaging Video

24. B. The Cell Cycle • Cell Cycle- a series of events a cell goes through as it grows and divides

25. 2. Prokaryotic Cell Cycle a. Not fully understood b. Steps • Growth • DNA replication • Cell Division – binary fission

26. d. Overview • Cells can divide quickly under good conditions • Most replicate their DNA once grown to a certain size • When DNA replication is complete, the cell divides

27. 3. Eukaryotic cell cycle • Has four parts: G1, S, G2, and M • Interphase- a long period of the cell cycle between one cell division and the next • Includes G1, S, and G2

28. c. G1 phase- cell growth • “G” stands for gap • Cell increases in size • Produces new organelles and proteins

29. d. S phase- DNA replication • “S” stands for synthesis • New DNA is synthesized when chromosomes are replicated

30. e. G2 phase- Preparing for Cell Division • Organelles needed for cell division are produced • At the end of G2, a cell is ready to divide

31. f. M phase- Cell division “M” stands for mitosis • Has two parts: mitosis and cytokinesis • Mitosis- the part of the eukaryotic cell cycle during which the nucleus divides • Cytokinesis- the part of the cell cycle in which the cytoplasm divides

32. 10.2 When do cells divide? • Describe the role of chromosomes in cell division. • Name the main events of the cell cycle.

33. 10.2 How do cells divide? • Describe what happens during the four phases of mitosis. • Describe the process of cytokinesis.

34. C. Mitosis • Mitosis is divided into 4 main phases • Prophase- “pro” = first • Metaphase- “meta” = middle • Anaphase- “ana” = to break • Telophase- “telo” = distance

35. 2. Events of each phase a. Prophase • Replicated chromosomes become visible • DNA strands are now called chromatids • Chromatid- one of two identical “sister” parts of a replicated chromosome • Centromere- an area where two sister chromatids are attached

36. Nuclear membrane breaks down • Spindle begins to form • Pairs of centrioles organize the spindle fibers

37. b. Metaphase • The chromosomes line up at the center of the cell • Spindle fibers connect the centromere of each sister chromatid to the spindle

38. c. Anaphase • The centromeres split, and the sister chromatids separate • A complete set of chromosomes move to opposite sides of the cell

39. d. Telophase • The chromosomes decondense • Nuclear membrane reforms around each group of chromosomes • Spindle begins to break apart

40. e. Cytokinesis- completes the cell division by splitting the cytoplasm and one cell into two identical cells • Happens differently in plant and animal cells

41. In animal cells, the cell membrane is pulled toward the center of the cell and the cytoplasm is pinched • In plant cells, the membrane is attached to the cell wall. • A cell plate forms between the two nuclei • Cell plate forms into new membranes and a cell wall forms between them

43. Let’s see this all together… Mitosis Animation 1 Mitosis Animation 2 Newt Lung Cell Mitosis

44. f. Big picture: mitosis is important for 2 main reasons • Growth • Repair

45. 10.2 How do cells divide? • Describe what happens during the four phases of mitosis. • Describe the process of cytokinesis.

46. 10.3 How does a cell control the process of cell division? • Describe how the cell cycle is regulated. • Explain how cancer cells are different from other cells.

47. Bone Fracture Activity

48. III. 10.3 Regulating the Cell Cycle • Controls on cell division • In multicellular organisms the cell cycle is carefully controlled • Ex: skin cells divide quickly • Ex: most muscle and nerve cells do not grow and divide

49. 2. Signals trigger cells to divide or to cease dividing • Ex: cells grown in culture will stop dividing when they touch another cell • When removed from the culture, they begin to grow and divide again b. Ex: Injury that heals- skin break, or broken bone

50. 3. Regulatory proteins- proteins that control the cell cycle • External regulators- proteins that respond to factors outside of the cell • Ex: growth factors control the healing process of a broken bone • Ex: Control the cell cycle of a developing embryo