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Cell Division and Growth

Cell Division and Growth. Chapter 10. How large can a cell be? Is there a limit?. DNA “overload” = when a cell becomes too large and an “information crisis” occurs Too difficult to exchange materials The speed of exchange is determined by the cell membrane.

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Cell Division and Growth

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  1. Cell Division and Growth Chapter 10

  2. How large can a cell be? Is there a limit? • DNA “overload” = when a cell becomes too large and an “information crisis” occurs • Too difficult to exchange materials • The speed of exchange is determined by the cell membrane

  3. What determines the rate of exchange of materials? • Surface area to volume ratio • The larger the surface area-to-volume ratio the more materials a cell can exchange with its environment

  4. Example problems • A cube with all sides 1 cm in length • A cube with all sides 2 cm in length

  5. What happens when a cell becomes too big? • The cell can die. • The cell can divide to produce two new daughter cells (cell division)

  6. Mitosis • Process in which a cell with a nucleus divides and forms two identical nuclei. • Refers to division of nucleus • Cytokinesis = division of the cytoplasm • Asexual Reproduction • One parent • Offspring identical to parent cell

  7. Nucleus review: • Control center • Location of genetic material • Chromatin = material of which chromosomes are composed • Histones = small groups of proteins where chromatin is found • Chromosome = short, thick, rod-like, chromatin structures

  8. Chromosome structure • Chromatid = each individual strand of a chromosome • Centromere = region where chromatids join.

  9. Mitosis is a continuous process which can be divided into phases.

  10. Interphase • Not considered a “phase” of mitosis. • Time when a cell is between mitotic cycles • Often called the “resting stage” • This is NOT an accurate description

  11. Events of Interphase: • Cell is growing in size • Proteins,organelles, and nucleic acids are produced • Majority of a cell’s “life” • Prepares for mitosis • Chromosomes and centrioles replicate.

  12. Relative lifetime of a cell:

  13. 1) Prophase • The double chromosomes are visible as threads that coil and contract into thick rods

  14. Events of prophase • Centrioles migrate toward opposite ends (poles) of the cell. • Microtubules extend from centrioles to form asters and eventually a spindle. • Toward end of prophase chromosomes begin to move to center (equator) of the cell • Nuclear envelope and nucleolus disappears

  15. Late Prophase:

  16. 2) Metaphase • Centromeres line up on equator • Two chromatids of each chromosome become separate chromosomes ANIMAL PLANT

  17. 3) anaphase • The duplicated chromosomes move to opposite poles • Microtubules help to move the chromosomes. ANIMAL PLANT

  18. 4) Telophase • Chromosomes uncoil and get longer • Spindle fibers disappear • Nuclear membrane forms around “daughter” nuclei. ANIMAL PLANT

  19. Review of mitosis • Mitosis Movie and tutorial

  20. Cytokinesis • Division of the cytoplasm. • Begins during late anaphase and finishes during telophase in animal cells.

  21. Controlling cell division • Do all cells divide at the same speed? • Why do cells divide at different speeds? • When do cells divide fastest during one’s life?

  22. Regulating division • Cyclins : proteins found in eukaryotic cells that regulate the timing of the cell cycle. • Internal regulators: proteins that work inside the cell • External regulators: proteins that respond to events outside the cell • growth factors, after injury, embryological

  23. Cancer • Defined as uncontrolled cell division. • If cells continue to divide over and over, eventually a mass of cells can be formed called a tumor that may interfere with normal tissuue or cellular functions.

  24. Assignment • Pages 257-259 Page 257-258 1-10,14,19,20,27,29 Page 259 1-12

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