PVHS HL Biology II Chapter 10 pictures and links removed by HC120727042224

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									  Chapter 10

Cell Growth and Division
                Chapter Outline
   Section 10.1
       Cell Growth
   Section 10.2
       Cell Division
   Section 10.3
       Regulating the Cell Cycle
                    Section 10.1
                    Cell Growth
   Section Outline
       Limits to Cell Growth
                     Section 10.1
                     Cell Growth
   Section Objectives
       10.1.1 Explain the problems that growth causes for
        cells.
       10.1.2 Describe how cell division solves the
        problems of cell growth.
                  Why do cells divide?
   Cells divide, instead of continuing to grow, for
    two main reasons.
       The larger a cell…
            … the more stress is placed on the DNA.
            … the more difficult it becomes to pass materials across
             the cell membrane.
                 Nutrients
                 Wastes and Synthesized Materials
Genetic Material
           DNA
               Adenine
               Thymine
               Guanine
               Cytosine
           RNA
               Adenine
               Uracil
               Guanine
               Cytosine
                     DNA “Overload”
   DNA stores genetic material or instructions
       Major Types of Cells
            Prokaryotic cells
                 Lack organelles (“specialized structures)
                     Example: DNA is found throughout the cytoplasm

            Eukaryotic cells
                 Contain organelles (“specialized structures”)
                    Example: nucleus which stores genetic material

                    Example: The larger a town gets…
             Exchanging Materials
   In order for materials to enter or leave the cell, the
    materials must pass across the plasma membrane (or
    cell membrane).
   The exchange rate depends on the surface area of the
    cell.
       Example: the larger the surface area, the more surface area
        is available for diffusion to occur
   The rate at which materials inside the cell are used up
    and waste produced depends on the volume within
    the plasma membrane.
                    Division of the Cell
   Cells divide to form “daughter” cells.
       Benefits
            Cell division begins with the replication of DNA.
                  This solves the genetic “overload” as cells grow.
                  Each daughter cell gets a copy of genetic material from the parent
                   cell.
            Cell division reduces the overall volume of the cell by dividing the
             materials within the plasma membrane relatively equally between
             daughter cells.
                  Materials can enter and exit the cell more easily since there is a
                   relatively larger surface area compared to the volume within the
                   newly divided cell.
            Cell division allows cells to work more efficiently.
End of Section 10.1
                     Section 10.2
                     Cell Division
   Section Outline
       Chromosomes
       The Cell Cycle
       Events of the Cell Cycle
       Mitosis
       Cytokinesis
                     Section 1.2
                     Cell Division
   Section Objectives
       10.2.1 Name the main events of the cell cycle.
       10.2.2 Describe what happens during the four
        phases of mitosis.
                    Cell Division
   In prokaryotes…
       … cell division is simple.
       … the materials within the plasma membrane are
        split equally among the new daughter cells.
   In eukaryotes…
       … cell division is complicated, with multiple
        stages regulated by the cell.
       … cell division occurs in two stages, mitosis and
        cytokinesis.
        Two Stages of Cell Division
   Mitosis
       The cell nucleus divides.
   Cytokinesis
       The cytoplasm within the plasma membrane is
        divided.
                  Chromosomes
   In eukaryotes…
       … genetic information is carried by chromosomes.
       … chromosomes are made of DNA.
       … each organism has a specific number of
        chromosomes.
                         Chromosomes
   Chromosomes are not visible except during
    cell division.
   Chromosomes condense during the initial
    stages of cell division.
       In cell division, chromosomes are replicated.
            Identical “Sister Chromatids” are formed.
                 These sister chromatids separate during cell division.
                 One chromatid goes to each of the new cells.
                       Chromosomes
   Centromere
       These structures hold each pair of chromatids together.
       Typically located near the middle of the chromatids.
            Example: Humans have 46 chromosomes.
            Example: Human cells entering cell division have 46
             chromosomes, each of which consists of two chromatids.
       The sequencing of entire sets of chromosomes result in the
        map of a genome.
        What is a chromosome?
   What is a chromosome?
   Reading Chromosomes
   Using Karyotypes to Predict Genetic Disorders
                  The Cell Cycle
   Interphase
       This is the “in-between” period between growth
        and the previous division of a cell.
               The Cell Cycle
   Cells grow.
   Cells prepare for division.
   Cells divide into daughter cells.
   This process can then be repeated.
             Events of the Cell Cycle
   Two Major Phases
       Interphase
            G1 – “Growth 1”
            S – “Synthesis”
            G2 – “Growth 2”
       M – “Mitosis”
                      G1 Phase
   Cells grow.
   Cells increase in size.
   Cells synthesize new proteins and organelles.
       “… extra materials needed to split into enough…”
                     S Phase
   Chromosomes are replicated.
   DNA molecules are synthesized.
   Proteins associated with the chromosomes are
    replicated.
   This is considered the “check point” of the cell
    cycle because cells which complete this phase
    usually continue through the remainder of the
    cell cycle.
                    G2 Phase
   Organelles and molecules required for cell
    division are produced.
   The is the final stage of interphase before a
    cell enters the stages of mitosis, or cell
    division.
                     Mitosis
   Occurs after interphase is complete.

   Four Major Phases
       Prophase
       Metaphase
       Anaphase
       Telophase
                                Prophase
   First and longest stage of mitosis.
       Requires ~50% of the time the cell is in the cell cycle.
   Chromosomes, made of condensed chromatin, become visible.
   Centrioles separate and take up opposite sides of the nucleus.
       Centrioles
            Centrioles are the two tiny structures in the cytoplasm near the nuclear
             envelope.
       Spindles
            Spindles are fan-like microtubules that separate the chromosomes.
            Spindles attach to the centromere of each chromatid.
   Chromosomes coil and the nucleolus disappears as the nuclear
    envelope breaks down.
                  Metaphase
   Typically only lasts a few minutes.
   Chromosomes line up across the center of the
    cell.
   Microtubules connect the centromere of each
    chromosome to the two parts of the spindle.
                  Anaphase
   The centromere that joins sister chromatids
    split.
   Sister chromosomes are separated.
   Chromosomes continue to move until they are
    separated near the pole of the spindle.
                   Telophase
   Chromosomes (still visible since they are
    condensed) begin to disappear.
   The nuclear envelope reforms to surround the
    genetic material as it unravels.
   Spindles begin to break apart.
   Nucleolus becomes visible.

   This ends mitosis but the process of cell
    division is not complete.
                              Cytokinesis
   This stage, within mitosis, involves the division of the cell’s
    cytoplasm.
   Occurs during telophase.
       In animal cells…
            … the plasma membrane is drawn inward.
            … “pinching” occurs.
            … each of the two resulting cells has a nucleus and organelles.
       In plant cells…
            … a cell plate forms midway between the two nuclei.
            … the cell plate gradually expands to separate the plasma membrane.
            … after the cell plate has completed this division, a cell wall begins to
             appear on the cell plate.
   Mitosis and Cytokinesis
   The Cell Cycle Game
End of Section 10.2
                 Section 10.3
           Regulating the Cell Cycle
   Section Outline
       Controls of Cell Division
       Cell Cycle Regulators
       Uncontrolled Cell Growth
                 Section 10.3
           Regulating the Cell Cycle
   Section Objectives
       10.3.1 Identify a factor that can stop cells from
        growing.
       10.3.2 Describe how the cell cycle is regulated.
       10.3.3 Explain how cancer cells are different from
        other cells.
          Controls on Cell Division
   Scientists can observe cell growth under
    laboratory conditions.
       Petri dishes that contain a single cell are filled with
        a nutrient solution.
       Cells will continue to grow until one cell comes in
        contact with another cell.
       If cells are removed from the center, cell growth
        will resume until contact occurs.
          Controls on Cell Division
   In humans…
       … at the site of injury, cells are stimulated to
        divide rapidly.
                Cell Cycle Regulators
   Is there a substance that can regulate the cell cycle?
       Early 1980’s
            Tim Hunt (England) – sea urchins research
            Mark Kirschner (United States) – cdk research
       Cells in mitosis contained a protein, that when injected into
        non-dividing cells, would cause a mitosis spindle to form.
       These newly injected cells would enter mitosis.
       This substance was called cyclin.
            Cyclin is the protein that is responsible for cell cycle regulation.
            Cell Cycle Regulators
   Two Major Types of Regulators
       Internal Regulators
       External Regulators
              Internal Regulators
   Proteins that respond to events inside the cell.
   Serve as “check points” within the cell.
       A cell will not enter mitosis if “process x” has not
        yet occurred.
   Apoptosis
       Programmed “cell death”
       Process which is controlled by the cell.
              External Regulators
   Proteins that respond to events outside the cell.
   Direct the rate at which the cell cycle
    progresses.
       Example: growth factors (embryo development)
       Example: wounds and healing (injury to the cell)
       Example: surface molecules and receptors tend to
        slow the division of cells by preventing excessive
        cell growth
         Uncontrolled Cell Growth
   Cancer
       Cancer cells do not respond to the signals that regulate the
        growth of most cells.
       Cancer cells divide uncontrollably.
            Tumors formation occurs.
            Cancer cells can “break away” from a mass and travel throughout
             the body. This process is called metastasis.
       Control over the cell cycle is lost.
            p53 gene connect?
                  p53 gene regulates the cell cycle until all chromosomes have been
                   replicated.
       Telomere Connections
           Treatment Options
   Chemotherapy
   Radiation Therapy
         Uncontrolled Cell Growth
   Environmental Factors
       Tobacco
       Radiation Exposure
       UV Radiation
End of Section 10.3

								
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