The Cell Cycle and Mitosis

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					        10-1 Cell Growth
Complete Guided Reading Workbook 10-1
              and 10-2
By the end of today you will be able to:

   Explain the problems that growth causes for

   Describe how cell division solves the
    problems of cell growth.

   Name and describe the main events of the
    cell cycle.
Let’s do some math!!!!
   Calculate the
    surface area of S.A. = 4 (pi) r 2
    each sphere.

   Calculate the
                                             Radius 2cm
    volume of each
    sphere.                                S.A. = ________
                                             Radius 2cm
                                           V = __________
   Then, calculate the                  S.A. = ___50cm2__
                                        Ratio SA:V = ________
    surface area to                       V = __33cm3____
    volume ratio. Round #’s
    up or down to make it easier.   Ratio SA:V = 50:33_or 1.51:1
   Radius 1cm
   Radius 1cm               Radius 2cm               Radius 3cm
   S.A. = _____
S.A. = __13cm2___      S.A. = ___50cm2__          S.A. = __113cm2_
                                                    S.A. = _____
   V = ______
 V = __4cm3____         V = __33cm3____              ___113cm3
                                                  V =V = _________
 Ratio SA:V ___
Ratio SA:V ==_13:4          Ratio SA:V =            Ratio SA:V =
                                                  Ratio SA:V = ___
    or 3.25:1__            50:33_or 1.51:1        _113:113 or 1:1__

       S.A. = 4 (pi) r 2

 1. As the spheres get larger what happens to the SA:V ratio?
1st problem:
Cell size and material exchange
   The larger a cell
    grows the more
    trouble it has…

       moving enough
        nutrients in

       Moving all the
        waste materials
2nd problem: DNA overload
   What are two problems that cell growth
    causes for cells?
       The larger a cell becomes, the more demands
        the cell places on its _____ and the more trouble
        the cell has moving enough _________and
        _________ across the cell membrane.

   What is viable solution for cells solve these
       Cell Division – A larger cell splits into two smaller
        daughter cells.
The Cell Cycle and Mitosis
          Chapter 10-2
 Homework 10-2-3 in guided reading
The Cell Cycle - series of events that cells
go through as they grow and divide

   The cell cycle is
    divided into two
      Interphase -
       period of the cell
       cycle between
       cell divisions
      M phase –
       period of time
       when mitosis
       and cell division
Parts of Interphase
   G1 Phase
      Growing
      Synthesize new proteins and
      Doing their jobs
      Longest phase of cell cycle
   S Phase
      Chromosomes(DNA) are
      Key proteins associated with
       replication are made
   G2 Phase
      Shortest of the 3 phases of
      Organelles and molecules for
       cell division are produced
      Check-up phase before mitosis
Chromatin and Chromosomes

 Chromatin - A complex of DNA and proteins
  in the cell nucleus that condenses to form
  chromosomes during cell division.
 Chromosomes – Condensed Chromatin
 They are the same stuff, just in different
Chromatin condenses in chomosomes
before mitosis begins

   Chromatin         Chromosomes

   Different organisms have different #’s of
        Humans    cells – 46
        Fruit Fly cells – 8
        Carrot cells – 18
        King Crab cells - 208
Chromosomes Replication
   During the cell cycle (before
    cell division can take place)
    chromosomes are replicated
    to form an identical copy of
   Two identical copies of a
    chromosome are called
    “sister” chromatids – (one of
    two identical “sister” parts
    of a duplicated
   Centromere - area where
    the chromatids of a
    chromosome are
M Phase, Cell Division and Mitosis

 Prophase

 Metaphase

 Anaphase

 Telophase

division and
other changes
exclusive of
division that
are a part of
mitosis or
  In plant cells, a cell plate forms. The cell plate is
  synthesized by the fusion of multiple membrane-
 bounded vesicles. Their fusion supplies new plasma
membrane for each of the two daughter cells. Synthesis
  of a new cell wall between the daughter cells then
                occurs at the cell plate.
10-3 cell cycle regulation

   Homework 10-3 guided reading workbook

 1. The break down of a cell’s entire life is the
  _______ ________.
 2. The phase of the cell cycle when the cell
  is growing, replicating DNA and getting ready
  for mitosis is _____________.
 3-6. What are the four phases of Mitosis?
 7. The process of a cell actually splitting in
  two is called _______________.
Controls on Cell Division
How do cells know when to divide
and when not to?
   Internal regulators – are proteins that
    respond to events inside the cell.
     Some proteins make sure cells do not enter
      mitosis until all of the chromosomes have been
     What stage of the cell cycle do you think these
      proteins work?
     G2 phase
   Cyclins – (internal regulator) one of a family
    of closely related proteins that regulate the
    cell cycle in eukaryotic cells

Protein that periodically
rises and falls in
concentration in step with
the eukaryotic cell cycle.
Cyclins activate crucial
protein kinases (called
cyclin-dependent protein
kinases, or CDK) and
thereby help control the
progression from one stage
of the cell cycle to the next.
    Cascade of events!!
External Regulators
   External regulators - Proteins that respond to
    events outside the cell are called external
   External regulators direct cells to speed up or slow
    down the cell cycle.
   Growth factors are among the most important
    external regulators, which tell cells to speed up
    division. When is this important?
   Molecules found on the surfaces of neighboring
    cells often have an opposite effect, causing cells to
    slow down or stop their cell cycles.
Uncontrolled Cell Growth
   Cancer cell
       Various forms of cancer have many causes
          Smoking
          Radiation
          Viral   infections

 The common thread in all cancers is that
  control over the cell cycle has broken down.
 Over 50% of cancer cells have a defect in
  the p53 gene.
Quiz on Thursday
HO due wednesday
p53 antioncogene
   p53 is a tumor
    suppressor gene
    found mutated in
    about half of
    human cancers.
   It encodes a gene
    regulatory protein
    that is activated by
    damaged DNA and
    is involved in
    blocking further
    progression of the
    cell cycle.
SRC, proto-oncogene tyrosine-protein kinase

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