1. Biology Chapter 10: Cell Growth and Division * This presentation contains copyrighted material.

2. THINK ABOUT IT – Limits to Cell Size 1.When a living thing grows, what happens to its cells? 2.What is there about growth that requires cells to divide and reproduce themselves? What are some of the difficulties a cell faces as it increases in size? The larger a cell becomes, the more demands the cell places on its DNA. In addition, a larger cell is less efficient in moving nutrients and waste materials across its cell membrane. 12/26/2015 Chap 10: Cell Growth and Division 2009

3. Information “Overload” –Living cells store critical information in DNA. –As a cell grows, that information is used to build the molecules needed for cell growth. –As size increases, the demands on that information grow as well. If a cell were to grow without limit, an “information crisis” would occur. 12/26/2015 Chap 10: Cell Growth and Division 2009

4. Information “Overload” –Compare a cell to a growing town. The town library has a limited number of books. As the town grows, these limited number of books are in greater demand, which limits access. –A growing cell makes greater demands on its genetic “library.” If the cell gets too big, the DNA would not be able to serve the needs of the growing cell. 12/26/2015 Chap 10: Cell Growth and Division 2009

5. Exchanging Materials –Food, oxygen, and water enter a cell through the cell membrane. Waste products leave in the same way. –The rate at which this exchange takes place depends on the surface area of a cell. –The rate at which food and oxygen are used up and waste products are produced depends on the cell’s volume. –The ratio of surface area to volume is key to understanding why cells must divide as they grow. 12/26/2015 Chap 10: Cell Growth and Division 2009

6. Ratio of Surface Area to Volume –Imagine a cell shaped like a cube. As the length of the sides of a cube increases, its volume increases faster than its surface area, decreasing the ratio of surface area to volume. –If a cell gets too large, the surface area of the cell is not large enough to get enough oxygen and nutrients in and waste out. 12/26/2015 Chap 10: Cell Growth and Division 2009

7. Traffic Problems –To use the town analogy again, as the town grows, more and more traffic clogs the main street. It becomes difficult to get information across town and goods in and out. –Similarly, a cell that continues to grow would experience “traffic” problems. If the cell got too large, it would be more difficult to get oxygen and nutrients in and waste out. 12/26/2015 Chap 10: Cell Growth and Division 2009

8. Division of the Cell –Before a cell grows too large, it divides into two new “daughter” cells in a process called cell division. –Before cell division, the cell copies all of its DNA. –It then divides into two “daughter” cells. Each daughter cell receives a complete set of DNA. –Cell division reduces cell volume. It also results in an increased ratio of surface area to volume, for each daughter cell. 12/26/2015 Chap 10: Cell Growth and Division 2009

9. Cell Division and Reproduction How do asexual and sexual reproduction compare? –The production of genetically identical offspring from a single parent is known as asexual reproduction. –Offspring produced by sexual reproduction inherit some of their genetic information from each parent. 12/26/2015 Chap 10: Cell Growth and Division 2009

10. –In multicellular organisms, cell division leads to growth. It also enables an organism to repair and maintain its body. –In single-celled organisms, cell division is a form of reproduction. Asexual Reproduction 12/26/2015 Chap 10: Cell Growth and Division 2009

11. Asexual Reproduction –Asexual reproduction is reproduction that involves a single parent producing an offspring. The offspring produced are, in most cases, genetically identical to the single cell that produced them. –Asexual reproduction is a simple, efficient, and effective way for an organism to produce a large number of offspring. –Both prokaryotic and eukaryotic single-celled organisms and many multicellular organisms can reproduce asexually. –-Bacteria cells reproduce by binary fission 12/26/2015 Chap 10: Cell Growth and Division 2009

12. Sexual Reproduction -In sexual reproduction, offspring are produced by the fusion of two sex cells – one from each of two parents. These fuse into a single cell before the offspring can grow. –The offspring produced inherit some genetic information from both parents. –Most animals and plants, and many single-celled organisms, reproduce sexually. 12/26/2015 Chap 10: Cell Growth and Division 2009

13. Biology notes-Chapter 813 Cell Division -Eukaryotes Two main types of division: 1.Mitosis- results in new cells with genetic material that is identical to the genetic material of original cell During: growth, development, repair, asexual reproduction (production of offspring from one parent) 2. Meiosis- occurs during the formation of gametes (reproductive cells, 1n), reduces the chromosome number by ½ in new cells, often combine to make 2n cells

14. Comparing Sexual and Asexual Reproduction 12/26/2015 Chap 10: Cell Growth and Division 2009

15. 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. 12/26/2015 Chap 10: Cell Growth and Division 2009

16. Let's start from the beginning... A long time ago our ancestors noticed that some things tended to reproduce themselves - traits were inherited. Unfortunately, that's not always a good thing!

17. What is a chromosome? Threadlike structure in nucleus > contains genetic information - passed on from one generation of cells to the next –Genetic information = DNA (“blueprints” of life) –DNA in form of a code (genes) > dictates everything from eye color to how long you live –“It’s in your genes” should actually be “It’s in your DNA

18. Gene Sequence of DNA that codes for a protein and determines a trait –Trait = specific characteristic that varies from one individual to another –Ex: height, hair and eye color Genes are the bands on chromosomes. –The thicker the band, the more information it holds.

21. Living things grow by producing cells. bacteria (0.5 to 1.5 microns) red blood cell (5 microns) lymphocyte (5 to 8 microns)

22. As a cell grows larger, it… Places more demands on its DNA –DNA “Overload” –Compare to town library (town grows, more demand for books) Has more trouble moving enough nutrients and wastes across its membrane (in and out of cell)

23. The cell will eventually divide into two daughter cells.

25. Cell Division Process by which a cell divides into two daughter cells –DNA replicated before division –Each daughter cell gets one complete set of genetic information Two stages: –Mitosis - nucleus divides to form two identical nuclei –Cytokinesis - cytoplasm divides to form two identical cells

26. Chromosomes Made up of DNA (genetic information) and proteins > chromatin Each chromosome has two identical “sister” chromatids - one goes to each new cell Cells of every organism have specific number of chromosomes –Ex: fruit flies 8, carrots 18, humans 46

27. Duplicated chromosomes are called dyads Duplicates held together by centromere Homologous pair = 1 of each pair acquired from one of the parents

29. The Cell Cycle Cell grows, replicates its DNA, and divides into two daughter cells Four phases ~M phase > Mitosis and cytokinesis (cell division) ~S phase > Synthesis (chromosome replication) ~G 1 and G 2 > “Gap” phases (periods of intense Growth and activity)

31. Interphase Period of cell cycle between cell divisions All phases except M –Made up of G 1, S, and G 2 phases –Split because M phase occurs much more quickly Includes: DNA replication, protein synthesis, and synthesis of organelles and materials needed for cell division

33. Mitosis > Process in which the nucleus divides to form two identical nuclei

34. Four Phases of Mitosis Prophase Metaphase Anaphase Telophase

35. Prophase Chromatin condenses into chromosomes Nucleolus disappears Centrioles separate –Two tiny “anchors” in cytoplasm near nuclear envelope Fanlike fibers extend to form spindle

36. Pair of Centrioles Centromere Chromosome (two sister chromatids)

37. Metaphase Chromosomes line up along center of cell –Each chromosome connected to spindle at centromere

38. (Imaginary line )

39. Anaphase Sister chromatids separate and move to opposite sides of cell

41. Telophase Chromosomes gather at opposite ends of cell Two new nuclear envelopes form

42. Chromosomes gathering New nuclear envelopes forming

43. Cytokinesis Cytoplasm pinches in half Each daughter cell has identical set of duplicate chromosomes

44. Cytokinesis in Animal Cells –The cell membrane is drawn in until the cytoplasm is pinched into two equal parts., Cleavage furrow –Each part contains its own nucleus and organelles. 12/26/2015 Chap 10: Cell Growth and Division 2009

45. 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. 12/26/2015 Chap 10: Cell Growth and Division 2009

46. Biology notes-Chapter 846

48. New individual cell

49. 10.1 Pre-Read Questions 1.Name 2 limitations to cell growth. 2.How does DNA limit cell growth? 3.Why is the ratio of surface area to volume important? 4.Describe the process of cell division.

50. Review: Cell Cycle Steps of Cell Division – Mitosis Prophase Metaphase Anaphase Telophase / Cytokinesis

51. Cyclin protein regulates the timing of the cell cycle in eukaryotic cells

52. Regulatory Proteins Two types 1.Internal Regulators 2.External Regulators

53. Internal Regulators proteins that respond to events inside the cell signals cell cycle to continue ONLY WHEN OTHER THINGS ARE COMPLETE

54. External Regulator proteins that respond to events outside the cell direct cells to speed up or slow down the cell cycle example: growth regulators

55. Apoptosis Cells die in one of two ways, they either die tragically from some unforeseen fashion, or they die from Apoptosis. This is the regularly scheduled death of a cell. Once it is triggered, the cells and chromatin shrink, the organelles are broken down and nearby cells clean up the mess. Apoptosis is key for development of tissue (you used to have a tail) and if it is triggered incorrectly, leads to other problems (AIDS)

56. Uncontrolled Cell Growth Cancer – body loses ability to control growth – does not respond to the regulator proteins – result = large masses of cells

57. Tumors masses of cells damages the surrounding tissues cells break off and spread throughout the body

58. Cause of cancer brought on by smoking tobacco radiation exposure viral infection etc

59. 10.3 Review Questions 1.Why is it important for cells to have regulated cell growth? 2.What is the purpose of the protein cyclin? 3.Compare and contrast internal regulators and external regulators. 4.What is cancer? What causes cancer?

60. Uncontrolled Cell Growth Cancer –Disorder in which some cells lose ability to control growth –Cells do not respond to signals that regulate growth of most cells –Result > divide uncontrollably and form masses of cells called tumors

61. Results of Mitosis Mitosis is the division of a NUCLEUS Mitosis produces two new nuclei with the SAME number of chromosomes as original nucleus Mitosis is ASEXUAL –ONE parent = 2 IDENTICAL daughters

62. The Stages of the Cell Cycle 12/26/2015 Chap 10: Cell Growth and Division 2009