Chapter 5 Cell Growth and Division by pptfiles


									Chapter 5:
Cell Growth and Division
Section 1:
The Cell Cycle
                   The Cell Cycle
 A series of growth, DNA duplication, and
  cell division which occurs in eukaryotes.
 Divided into 2 Major Parts
    – Interphase

    – Mitosis
    The majority of a cell’s life.
    Three parts of interphase:
1.   Gap 1 (G1):
     – Normal cell functions / increase in size and
       number of organelles
     – Most of a cell’s life
     – A signal must be accepted telling the cell it’s
       ready to continue to the next stage.
          A “checkpoint”
          Interphase Continued
2.   Synthesis (S):
      The cell duplicates its DNA. Readies itself
       for cell division.
3.   Gap 2 (G2):
      Continued growth and normal functioning
      Another checkpoint before continuing
   Two processes:
    1. Mitosis: the division of the nuclei to form 2
       new identical nuclei.
    2. Cytokinesis: the division of the cytoplasm to
       form 2 identical daughter cells.
              Cell Cycle Rates
 The length of the G1 stage is different for
  different cells:
 Children: Short G1; cells are needed to
  grow the organs and body larger.
 Skin and Intestinal Lining: Short G1; need
  to replace cells.
 Nerve Cells: Never divide after a certain
    – “Stuck” in a G0 stage
   S, G2, and Mitosis take about 12 hours.
                    Cell Size
   A cell’s size is limited to a ratio of surface
    area to volume.
    – As a cell increases in size, volume increases
      faster then volume.
    – Not enough surface area to provide adequate
      exchange with the environment.

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