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Cell Growth and Division The Cell Cycle & Mitosis

Cell Growth and Division The Cell Cycle & Mitosis. Why do cells divide???. DNA can only manage the contents of a small cell . The cell can’t move food/wastes across a membrane of a large cell As a cell gets bigger, its volume increases faster than its surface area.

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Cell Growth and Division The Cell Cycle & Mitosis

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  1. Cell Growth and DivisionThe Cell Cycle & Mitosis

  2. Why do cells divide??? • DNA can only manage the contents of a small cell. • The cell can’t move food/wastes across a membrane of a large cell • As a cell gets bigger, its volume increases faster than its surface area.

  3. Why can’t cells grow forever? • REASON 1: Not enough DNA!...as the cell increases in size, it keeps the same amount of DNA. Eventually the cell will grow too much for the DNA to control all its activities Memory Trick: Think of DNA like a library of books. If a town (cell) is too big, people may have to wait for books!

  4. Why Can’t Cells Grow Forever? • REASON #2:Surface area of membrane doesn’t increase as quickly as cell volume Too little membrane not enough exchange of materials in and out of the cell

  5. Cell Division or Mitosis • Before a cell gets too big, it splits into daughter cells. • The two daughter cells are identical to each other (they’re like twins!)

  6. Cell Division in Prokaryotes • DNA is copied and divided into two cells • Creates two identicaldaughter cells • Process is called Binary Fission

  7. DNA is found in the nucleus Chromatin is DNA & protein threads that coil into chromosomes during cell division. Cell Division in Eukaryotes

  8. Cell Division in Eukaryotes: The Cell Cycle • Cell Cycle:The series of events that cells go through as they grow and divide. • G1 Phase: cell grows/makes new proteins and organelles • S Phase: DNA copied

  9. The Cell Cycle • G2 Phase: Organelles/molecules for cell division are made • M Phase (Mitosis): Cell divides into 2 daughter cells

  10. Structure of Chromosomes • Coiled threads of DNA and proteins. • Contains genes (hereditary information) • Must successfully divide for new cells to be made

  11. Structure of Chromosome Chromatids: 2 identicalcopies Of DNA that are connected to Form a chromosome Centromere:the area where chromatids are attached (usually at the middle of the chromatids)

  12. Basic Definitions Centromere Chromatid Chromosome

  13. Chromosome #’s • The cells of every organism have a specific number of chromosomes

  14. Diploid vs. Haploid Cells • Diploid Cells (2n)= 2 sets of chromosomes…one from each parent (Example: human body cell) • Haploid Cells (n)= only have 1 set of chromosomes (Example: Sperm or Egg Cell)

  15. Types of Chromosomes • Sex chromosomes = determine the sex of an organism; either X or Y • Autosomes =all the other chromosomes in an organism

  16. Cell Cycle • The series of events that cells go through as the grow and divide • During the cycle, a cell grows, prepares for division, and divides to form 2 daughter cells, each of which then begins the cycle again • 2 Main Parts 1) Interphase 2) Cell Division

  17. Interphase • Time between divisions where cell grows and replicates DNA • 3 Parts 1) G1 = cell grows and matures 2) S = DNA is copied 3) G2 = cell prepares for division http://www.cellsalive.com/cell_cycle.htm

  18. Before Mitosis • Interphase (includes G1, S and G2) = Time between divisionswhere cell grows and replicatesDNA.

  19. Mitosis • This involves divisionof the nucleus • 4 Phases 1) Prophase 2) Metaphase 3) Anaphase 4) Telophase

  20. The Steps of Mitosis • Prophase= • Coiling of DNA into chromosomes • Nuclear membrane breaks down • Spindle forms

  21. What is the spindle? • 2 Structures located in the cytoplasm called centriolesmove towards opposite sides of the nucleus • Microtubules (protein tubes) called spindle fibersgrow from the centrioles • Spindle fibersattach to chromosomes at the centromere and help pull chromatids apart

  22. The Steps of Mitosis • Metaphase = Spindle fibers move chromosomes to the center of the dividing cell.

  23. The Steps of Mitosis • Anaphase = Chromatids of each chromosomeseparate at the centromere and move toward opposite poles of the dividing cell

  24. The Steps of Mitosis • Telophase = • Chromosomes reach poles of cell • Spindle breaks down • Chromosomes uncoil into chromatin • Nuclearenvelopes and 2 nucleoli form

  25. The Steps of Mitosis • Cytokinesis= Division of the cytoplasm • Animal Cell:Cleavage Furrow (cell membrane pinches in )

  26. The Steps of Mitosis • Cytokinesis = Division of the cytoplasm • Plant Cell:Cell Plate (cell wall grows between daughter cells)

  27. Mitosis in Real Cells http://www.cellsalive.com/mitosis.htm ..\..\..\Downloaded Videos\The Stages of Mitosis.avi ..\..\..\Downloaded Videos\Cell Division and the Cell Cycle.avi

  28. Life Spans of Human Cells

  29. Questions to think about… • White blood cells help protect the body from infection/disease. How might their function relate to their life span? • 10 hrs: common everyday germ • 40 years: These cells recognize some bacteria/viruses your whole life and kill them

  30. Questions to think about… • Based on the data, how are the consequences of injuries to the spine and heart similar to each other? • Can’t make new cells • Permanent damage

  31. Questions to think about… • Suggest a hypothesis that explains the life spans of the lining of the esophagus, small intestine and large intestine. • Acid kills some cells • A lot of food passes thru them • Cells are easily damaged

  32. Questions to think about… • Cancer is a disease related to cell life span and cell division. If cancer were added to the data table, predict what would be written under the columns “Life Span” and “Cell Division” • Life Span: long • Cell Division: rapid

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