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Something to think about...

Something to think about. When you see a newborn baby, is it hard for you to imagine that just nine months ago, that baby was a single cell?. When you see a towering oak tree, can you believe that it was once a measly acorn?.

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Something to think about...

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  1. Something to think about... When you see a newborn baby, is it hard for you to imagine that just nine months ago, that baby was a single cell? When you see a towering oak tree, can you believe that it was once a measly acorn? When you mow the lawn on Saturday, can you believe that by next Saturday, you have to do it again? Can you believe that every second, your body makes 25 million new cells?

  2. Cell Growth and Reproduction

  3. What Limits Cell Size? Why can’t organisms be just one giant cell? 1 Diffusion 2 DNA Content 3 Surface Area to Volume Ratio

  4. Diffusion  = Mitochondrion Waste Waste Oxygen   Glucose  Cells can metabolize only as quickly as they receive raw materials.  An average-sized cell with a diameter of 20um will receive supplies in a fraction of a second. What if the cell were 20cm in diameter? So long, big cell!

  5. DNA Content  Most cells contain only one nucleus responsible for programming all metabolism. DNA RNA  If the ribosomes don’t receive enzyme and protein-making instructions from the RNA, guess what? So long, big cell!

  6. Surface Area-to-Volume Ratio  As a cell’s size increases, its volume increases much faster than its surface area. Volume l x w x h Surface Area l x w x # sides 3 cm 2 cm 1 cm3 6 cm2 1 cm 27 X 9 X 8 cm3 24 cm2 You Know! So long, big cell! 27 cm3 54 cm2

  7. So, what must the cell do? DIVIDE

  8. Cell Cycle G1, S, and G2 = Interphase Prophase, Metaphase, Anaphase, Telophase = Mitosis IPassed My Algebra Test G1 -- Period of cell growth before DNA is duplicated S -- period when DNA is duplicated Telophase G2 -- period after DNA is duplicated; cell prepares for division; end of interphase Anaphase Metaphase Prophase

  9. Interphase  The cell is engaged in metabolic activity and performing its preparation for mitosis. Chromosomes are not clearly visible in nucleus, but the nucleolus may be visible. Centrioles (or microtubule organizing centers) may be visible during this phase. nucleus nuclear membrane chromatin

  10. Prophase Chromatin in the nucleus begins to condense and becomes visible in light microscope as chromosomes. Nucleolus disappears. Centrioles begin moving to opposite ends of the cell and fibers extend from the centromeres.

  11. Interactive Eye, LLC (1997) [Site Name] Prophase • Type your welcome message here. You can make this a long message, or something short. Be sure to include a brief description of the type of things that can be found at this location. Custom Topic A Custom Topic B Vital Statistics Favorite Links to Visit

  12. Metaphase Spindle fibers align the chromosomes along the middle of the cell nucleus, or plate. • This organization ensures that in the next phase, each new nucleus will receive one copy of each chromosome.

  13. Interactive Eye, LLC (1997) Metaphase

  14. Anaphase  The paired chromosomes separate at the kinetochores and move to opposite sides of the cell.

  15. Interactive Eye, LLC (1997) Anaphase

  16. Telophase  Chromatids arrive at opposite poles of the cell and new membranes form around the daughter nuclei.  Chromosomes uncoil and are no longer visible under the light microscope. Cytokinesis begins. Cell Plate or Cleavage Furrow

  17. Interactive Eye, LLC (1997) Telophase

  18. Cytokinesis In animal cells, cytokinesis results when a cleavage furrow forms and pinches the cell in two. In plant cells, cytokinesis occurs when a rigid wall, called a cell plate, forms between the two daughter cells.

  19. Interactive Eye, LLC (1997) Cytokinesis

  20. Cell Reproduction  Following the completion of the cell cycle, two daughter cells result, with the same number of chromosomes as the parent cells. 46 46 14 46 14 46 46 46 46 46 14 14 HUMAN GORILLA GARDEN PEA

  21. So… What Are The Results? Genetic continuity, i.e., two new cells with chromosome sets identical to the parent cell. Daughter cells will carry out the same cellular processes and functions as their parent cell and will grow until the limitations of cell size force them to divide.

  22. To Review... • Limits of Cell Size • Diffusion • DNA Content • Surface Area-to-Volume Ratio • Cell Cycle • Interphase • Mitosis (Nuclear Division) • Prophase, Metaphase, Anaphase, Telophase • Cytokinesis (Cytoplasmic Division)

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