Chapter 6 Chromosomes and Cell Reproduction by dffhrtcv3


									Chapter 10
Cell Growth and Division

                CPI Biology
                Holliston High School
10-1 Limits to Cell Growth
 When a living organism grows what
 happens to its _______________?
   A) they get larger and ___________
   B) they _______________in numbers
   C) they get bigger and there are more

 ANSWER: B! The cells of an adult are
 they same as a young animal…just a lot
 more of them.
Why don’t cells get bigger?

 2 reasons:
 1. ___________   “OVERLOAD”
DNA “Overload”

  DNA carries all of the information that
   _________________ the cell’s structure
   & function
  If a cell ______________ in size, it’s
   DNA cannot keep up with all of the cell’s
   needs… “information crisis!”
  DNA is similar to a ________________;
   if a town grows, people need to wait in
   order to take out a book
Exchanging Materials

  Nutrients such as food, water, O2 need
   to enter the cell through the __________
  Wastes must ___________
  This rate of exchange depends on
   surface area of cell (total area of cell
   membrane) as well as the volume of the
  As cells get larger, it gets more difficult to
   exchange materials
Ratio of Surface Area to Volume

        Cell Size

 Surface Area
 (length x width x 6)

(length x width x height)
Ratio of Surface Area
to Volume
Ratio of Surface Area to Volume

  As a cell gets bigger, the ____________
   increases much more rapidly than the
   _______________ __________
  This causes the RATIO to decrease
   which causes problems in the exchange
   of materials
  If cell is ___________ large, it is difficult
   to move nutrients and wastes in and out
   of a cell
Reasons to Divide
Division of the Cell

  CELL DIVISION: before it becomes too
   large, a growing cell “parent” divides
   forming two “daughter” cells
  1st DNA is ________________ so each
   daughter cell can get it’s own copy
  Daughter Cells have an increased ratio
   of surface area to volume which allows
   efficient exchange of material with the
10-2 Cell Division

    Before a cell divides, DNA needs to be copied
     so that each daughter cell has it’s own
     complete set of ____________________

  __________________: simple division of cell
  __________________: 2 stages
     MITOSIS: division of cell nucleus

     CYTOKINESIS: division of cytoplasm
Asexual Reproduction

    Reproduction by mitosis & cytokinesis is
     also known as asexual reproduction
    ______________ cells genetically
     identical to ______________ cells
    Most __________________ organisms
     reproduce this way
 Made of DNA and ____________
 Cells of an organism have a specific #
  of chromosomes
    humans = ________

    fruit flies = 8

    carrots = 18

 Only visible during cell division when
  the ______________ condenses
 _____________________: where
  chromatids are attached
                                     • Before cell division,
a One chromosome (not copied)        chromosomes replicate
                                     to form 2 identical
                                     “sister” chromatids
                                     • Separate from each
                                     other when cell divides

                                one chromatid   two sister
                                one chromatid
b One chromosome (copied)
The Cell Cycle
   CELL CYCLE: series of events cells go through as
   they grow and divide; consists of 4 phases:
  1.  _____________: mitosis & cytokinesis (cell division)
  2.  _____________: intense growth; synthesis of
      proteins and organelles
  3.  _____________: chromosome replication &
      synthesis of DNA molecules; once a cell enters this
      phase, it will complete the whole cycle
  4.  _____________: shortest phase where cell
      prepares to divide; organelles & molecules already
            INTERPHASE = G1 + S + G2 phases
The Cell Cycle
 ______________ = G1 + S + G2 phases
 Longest part of cycle
 Cell increases in mass
                                        G1 phase
 Cytoplasmic components
 DNA is copied
                    M phase
                                                   S phase

                                   G2 phase
MITOSIS – division of the cell nucleus

                   PROPHASE    METAPHASE

                    ANAPHASE   TELOPHASE

    1st & longest phase
    ____________ become
    centrioles ___________
    chromosomes attach to
     fibers in spindle
    ____________
    nuclear envelope breaks

                     Centrioles are
                      organelles that
                      help organize the
                      microtubules that
                      help separate
                      (spindle fibers)

                     Plants don’t have

  2nd phase
  Chromosomes line
   up _____________
   center of cell
  Microtubules
   connect the
   of each chromosome
   to the centrioles
  3rd phase
  centromeres split,
   separating sister
   into separate
  Chromosomes move to
   opposite poles
  Phase ends when
   4th & last phase
   _________________
   Nuclear envelope
   Spindle breaks down
   Nucleolus forms
   __________ is complete
    but cell division is not
    done yet…what happens
Cytokinesis – division of cytoplasm
  2 nuclei have been formed in mitosis with duplicate
   copies of DNA  need to ___________ cytoplasm
  In Animal Cells: cell membrane is drawn in until
   _________________ is pinched into two parts
Cytokinesis in Plant Cells

    ____________________ forms between the
    nuclei and develops into a separating
    membrane, cell wall forms in the cell plate
Interphase    Early Prophase        Late Prophase   Prometaphase

               pair of centrioles


Metaphase   Anaphase   Telophase   Interphase
10-3 Regulating the Cell Cycle

  Not all cells go through cell cycle at
   ____________ rate
  (ex) muscle & nerve cells
   ___________ divide once developed
  (ex) skin & blood cells divide
  Cell growth and cell division are carefully
Controls on Cell Division
  Cells that come in contact with other cells stop
  Controls on cell growth and cell division can be
   turned on and off
  When you get a cut, skin cells divide rapidly  start
   the healing process
Cell Cycle Regulators

  ___________: proteins that regulate the
   timing of the cell cycle in eukaryotic cells
  When injected into a non-dividing cell,
   cyclins start mitosis
      A sample of    The sample is injected
      cytoplasm is   into a second cell in G2
      removed from   of interphase.
      a cell in                                 As a result, the
      mitosis.                                  second cell
                                                enters mitosis.
Internal Regulators

  proteins that respond to events
   ________ the cell
  allow cell cycle to proceed only if certain
   processes (CHECKPOINTS) have
   happened inside the cell
   (ex) cell will not enter mitosis until all
   chromosomes are replicated
External Regulators

  Proteins that respond to events ___________
   the cell
  Direct cells to speed up or slow down cycle
  __________________: very important
   external regulators that stimulate the growth
   and division of cells
     (ex) embryonic development & wound healing
    Molecules on surface of neighboring cells
     have opposite effect (slow down or stop
     cycle) to prevent excessive cell growth
Uncontrolled Cell Growth
   _____________:
    disorder in which the
    body’s own cells lose the
    ability to control growth         Healthy lung

   Cancer cells do not
    respond to cell cycle
   Causes: tobacco,
    radiation, viruses
                        Lung Cancer
 _____________: masses of cells formed
  from uncontrolled division; may damage
  surrounding tissues (aka – neoplasms)
 Sometimes caused by a checkpoint gene
  ________________ and control over cell
  division is lost.
 Cancer cells may break loose from
  tumors  spread throughout body 
  disrupt normal activities
   Benign               Malignant
   Tumor                Tumor

                 1. Cancer cells slip
                 of out their home
2. The           tissue
cross the wall
of a blood or
lymph vessel.    3 Cancer cells tumble
                 along inside blood
                 vessels, then leave the
                 bloodstream & start
                 new tumors in new
p53 GENE
 What does this gene do?
  Produces proteins that stop the cell cycle until
   all chromosomes are replicated
 What happens when p53 is defective?
  Cells do respond to signals that would
   normally control their growth
 Can a defect in p53 cause cancer?
  There is a high incidence of cancerous cells
   linked to a defective p53 gene

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