Chapter 9 Cellular Reproduction

2. Chapter 9 Cellular Reproduction Section 1: Cellular Growth Section2: Mitosis and Cytokinesis Section 3: Cell Cycle Regulation

3. Objectives: Explain why cells are relatively small. Summarize the primary stages of the cell cycle. Describe the stages of interphase. 9.1 Cellular Growth

4. Main Idea – Cells grow until they reach their size limit, then they either stopgrowing or divide. 9.1 Cellular Growth

6. 1. Most cells are smaller than the period at the end of this sentence. 2. The key factor that limits the size of a cell is the ratio of its surface area to its volume.

7. 3. The surface area of the cell is the area covered by the plasma membrane. To calculate the surface area of the cube multiply L x W x number of sides (6)

8. 4. The volume refers to the space taken up by the contents of the cell. To calculate the volume, multiply L x W X H 5. As a cell grows, it’s volume increases more rapidly than the surface area. As a cell increases in size the surface area to volume decreases

9. Cellular Reproduction Chapter 9 9.1 Cellular Growth Ratio of Surface Area to Volume

10. If a cell is too large it may have difficulty supplying nutrients and expelling waste products. • Cells remain small to maximize the ability of diffusion and motor proteins to transport nutrients and waste products.

11. Small cells maintain more efficient transport systems. • The need for signaling proteins to move throughout the cell also limits cell size. • Cell size affects the ability of the cell to communicate instructions for cellular functions.

12. Cells reproduce by a cycle of growing and dividing.

13. In the cell cycle, a cell stays in Interphase the longest 12.There are three main stages of the cell cycle interphase, mitosis, and cytokinesis.

14. Diagram of cell cycle – see pg. 246

15. Cellular Reproduction Chapter 9 9.1 Cellular Growth • Interphase is the stage during which the cell grows, carries out cellular functions, and replicates. • Mitosis is the stage of the cell cycle during which the cell’s nucleus and nuclear material divide. • Cytokinesisis the method by which a cell’s cytoplasm divides, creating a new cell.

16. 13. The duration of the cell cycle varies, depending on the cell that is dividing. • For most normal, actively dividing animal cells, the cell cycle takes approximately 12-24 hours.

17. 15. During interphase, the cell grows, develops into a functioning cell, duplicates it’s DNA, and prepares for division.

18. 16.Interphase is divided into 3 stages G1, S, G2.

19. 17. Chromosomes – contain genetic material. Chromatin – relaxed form of DNA in nucleus copies it’s DNA in preparation for cell division.

20. 18. In mitosis, the cell’s nuclear material divides and separates into opposite ends of the cell. 19. In cytokinesis, the cell divides into 2 daughter cells, with identical nuclei.

21. 20. The cell cycle is the method by which eukaryotic cells reproduce themselves. 21. Prokaryotic cells, reproduce by a method called binary fission.

22. Objectives: Describe the events of each stage of mitosis. Explain the process of cytokinesis. Main Idea Eukaryotic cells reproduce by mitosis, the process of nuclear division, and cytokinesis, the process of cytoplasm division. 9.2 Mitosis and Cytokinesis

23. Mitosis • The key activity of mitosis is the accurate separation of the cell’s replicated DNA. • The process of mitosis increases the number of cells as a young organism grows to its adult size. • Organisms also use mitosis to replace damaged cells.

24. The Stages of Mitosis 4. The 4 stages of mitosis are: prophase, metaphase, anaphase and telophase.

25. Cellular Reproduction Chapter 9 9.2 Mitosis and Cytokinesis The Stages of Mitosis • Prophase- the first stage of mitosis—cell spends most of its time here

26. 5. Chromatin tightens or condenses into chromosomes. This action facilitates chromosome movement. 6. As prophase continues, the nucleolus seems to disappear.

27. 7. Microtubule structures called spindle fibers form in the cytoplasm. 8. Near the end of prophase, the nuclear envelope disappears.

28. Cellular Reproduction Chapter 9 9.2 Mitosis and Cytokinesis Metaphase 9. Sister chromatids are pulled by motor proteins along the spindle apparatus toward the center of the cell and line up in the middle, or equator of the cell.

29. Cellular Reproduction Chapter 9 9.2 Mitosis and Cytokinesis Anaphase 10. The chromatids are pulled apart. 11. At the end of anaphase, the microtubules, with the help of motor proteins, move the chromatids toward the poles of the cell.

30. Cellular Reproduction Chapter 9 9.2 Mitosis and Cytokinesis Telophase 12. Chromosomes arrive at the poles of the cell and begin to relax or decondense. 13. Two new nuclear membranes begin to form and the nucleoli reappear.

31. Cytokinesis– process that divides the cytoplasm 14. This results is 2cells, each with identical nuclei.

32. 15. In animal cells, cytokinesis is accomplished by using microfilaments to constrict or pinch the cytoplasm.

33. 16. In plant cells, a new structure called a cell plate forms between two daughter cells. Cell walls then form on either side of the cell plate.

34. Prophase – “poles form” (centrioles) chromosomes condense; spindle forms Metaphase – “meet in the middle” chromosomes line up at the equator Anaphase – “pull apart” chromosomes move to opposite poles Telophase – “pinch together” nuclear envelope forms; chromosomes decondense The 4 Stages of Mitosis http://www.johnkyrk.com/mitosis.html

37. I Interphase Probably Prophase Make Metaphase A Anaphase Teacher Telophase Crazy Cytokinesis http://www.johnkyrk.com/mitosis.html Remember the Stages of Cell Division

38. Prokaryotic cells undergo binary fission- cell divides into 2 genetically identical cells WHY? Prokaryotic cells do not have a nucleus. Mitosis is division of the nucleus.

39. Binary Fission - lhs.lps.org

40. 2. Mitosis

42. Objectives: Summarize the role of cyclin proteins in controlling the cell cycle. Explain how cancer relates to the cell cycle. Describe the role of apoptosis. Summarize the two types of stem cells and their potential uses. Main Idea - The normal cell cycle is regulated by cyclin proteins. 9.3 Cell Cycle Regulation

43. CELL DIVISION GENES • The rate of cell division varies depending on the type of cell. • Some cells divide frequently • (some human skin cells divide once/hour) • Some cells divide occasionally • (liver cells divide about once/year) • Some cells don’t divide once they form (nerve cells)

44. A mechanism involving proteins and enzymes control the cell cycle.

45. 2. These proteins are called cyclins because they regulate the timing of the cell cycle in eukaryotic cells.

46. 3. Cyclinsbind to enzymes called cyclin-dependent kinases(CDKs) to start various activities that take place in the cell cycle.

47. 4. Cyclin/CDK combinations occur only during the stages of interphase and mitosis.

48. 5. Different cyclins/CDK’s combinations control different activities at different stages in the cell cycle.

49. 6. The different cyclin/CDK combinations signal the start of the cell cycle, DNA replication, protein synthesis, nuclear division and the end of the cell cycle.

50. 7. The cell cycle also has built in checkpoints that monitor the cycle and can stop it if something goes wrong.