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D86083-Chapter 10 - Cell Growth and Division

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					           Chapter 10 – Cell Growth
                and Division
   Limits to cell growth
      As cell grows it places greater demands on DNA


       The cell has trouble moving nutrients and waste
        across the cell membrane

       Ratio of surface area to volume is extremely
        important
          Volume increases much more rapidly than the
           surface area
          Cell division takes place before cell becomes too
           large
 Cell Sizes




Surface Area                                   54 cm2
lengthxwidthx6        6 cm2   24   cm2

Volume                                           27cm3
Lengthxwidthxheight   1 cm3   8 cm3
Ratio of surface        6:1        3:1   2:1
area to volume
                  Cell Division
   Chromosomes
       Carries the genetic information from one
        generation to the next
       Made up of DNA
       Replicated prior to cell division
       Consists of two “sister” chromatids
       Attached by a structure called a centromere
I. Chromosomes
 1. Chromosomes are composed of DNA and
Proteins (histones) and carry the genetic
information in eukaryotic cells.
 a. Each species of organism has a specific
number of chromosomes.
1. Drosophila melanogaster has 8
chromosomes
2. Humans have 46 chromosomes
                        ____ visible
b. Chromosome arenot __________
                                  chromatin
except during cell division. (known as
___________ when not dividing)
c. Replication (copying) of the DNA occurred
  before cell division
_______________________ therefore every
chromosome is actually two identical “______”
                                       sister
chromatids
d. Each pair of chromatids is connected to
each other at an area called the
 centromere
___________, usually located near the center
of the chromosome.
                           centromere



                             Sister
                             chromatids

http://www.biostudio.com/demo_freeman_dna_coiling.htm
                    Cell Cycle
   A cell grows, prepares for division, and
    divides to form two daughter cells, each of
    which begins the cycle again

   Consists of four phases:
       M phase – mitosis
       G1 phase – cell growth
       S phase – DNA replication
       G2 phase – preparation for mitosis
               G1



M-phase
                    s



          G2
                    Mitosis
   Prophase – chromatin condenses, centrioles
    separate, spindle forms, nuclear membrane
    breaks down
   Metaphase – Chromosomes line up across the
    center of the cell
   Anaphase – sister chromatids separate and are
    moved apart
   Telophase – chromosomes gather at opposite
    ends, new nuclear membranes form
                Cytokinesis
   The division of the cytoplasm of the cell
   In animal cells the cell membrane is drawn
    inward until the cytoplasm is pinched into
    two new cells
   In plant cells a cell plate forms midway
    between the divided nuclei; the cell plate
    gradually develops into a separating
    membrane
       Regulating the Cell Cycle
   When cells come into contact with other
    cells they respond by not growing

   Controls on cell growth and cell division
    can be turned on and off

   In an injury cells at edge of injury are
    stimulated to divide rapidly to begin
    healing
         Cell Cycle Regulators
   Cyclin – protein that regulates the timing
    of the cell cycle in eukaryotic cells
   Internal Regulators – respond to events
    inside the cell
   External Regulators – respond to events
    outside the cell
   Uncontrolled Cell Growth – form masses of
    cells called tumors that can damage the
    surrounding tissue
          Stem Cell Research
   Stem Cells can develop into any number
    of specialized cells
   Implants of stem cells can reverse the
    effects of some injuries
   It may also be possible to use stem cells
    to grow new liver tissue, replace heart
    valves, and to reverse the effects of
    diabetes
   Can be collected from embryonic tissue

				
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