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Chapter 9 Cellular Reproduction

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* Length of Cell Cycle Each cell type has a specific growth and reproduction time ... Phases of Mitosis Prophase ... the cytoplasm Plants ... – PowerPoint PPT presentation

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Title: Chapter 9 Cellular Reproduction


1
Chapter 9 Cellular Reproduction
  • 9.1 Cellular Growth

2
Cells Come in Different Sizes
  • Red Blood Cell 8 um in diameter
  • Nerve Cell 1 m in length with very small diameter
  • Yolk of ostrich egg 8 cm
  • Most cells are 2-200 um
  • 1000 um 1 mm

3
Limits to Cell Size
  1. Diffusion
  2. DNA
  3. Surface to volume ratio

4
Diffusion Limits Cell Size
  • Within the cell nutrients must diffuse to all
    parts
  • Diffusion is based on random movement of
    particles
  • Diffusion is too slow for a large cell
  • When cells reach maximum size they die or divide

5
DNA Limits Cell Size
  • DNA contains all the instructions for
    synthesizing proteins (including enzymes)
  • Large cells would need more proteins
  • More copies of the DNA instructions would be
    needed for a large cell
  • Most cells contain only one set of DNA

6
Surface Area to Volume Ratio Limits Cell Size
  • As the size of a cell increases the volume
    increases faster than the surface area
  • If the cell size is doubled then need eight times
    more nutrients but plasma membrane is only four
    times larger
  • Cells divide before they become too large to
    function properly

7
Volume Increases Faster than Surface Area
What are the surface area to volume ratios?
8
The Cell Cycle
  • Sequence of growth and division of a cell
  • Two main periods
  • Growth also called interphase
  • Division also called mitosis and cytokinesis

9
Cell Cycle
10
Interphase
  • NOT part of mitosis, rather the time between one
    mitosis and the next
  • Stages of interphase
  • G1 phase rapid growth and metabolic activity
  • S phase synthesis of DNA (additional copy is
    made)
  • G2 phase centrioles and other organelles
    replicate cell prepares for division

11
Chromosomes and Chromatin
  • Both are DNA
  • Chromosomes are the condensed form of DNA that is
    visible as individual strands.
  • Chromatin is the relaxed very thin form of DNA
    that is not visible as individual strands.
  • During interphase DNA is in the chromatin form.

12
Chromosomes and Chromatin
Chromatin DNA form
Chromosome DNA form
Chromatin DNA form
13
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14
Cell Reproduction
  • Process of producing new cells from preexisting
    cells
  • Three Types
  • Fission bacteria
  • Meiosis sex cells
  • Mitosis body cells
  • Needed for growth
  • Needed for repair

15
Bacteria Reproduce by Fission
  • Prokaryotes do not have a nucleus
  • They divide the cell contents then divide

16
Chapter 9 Cellular Reproduction
  • 9.2 Mitosis and Cytokinesis

17
Eukaryote Cell Reproduction is Mitosis and
Cytokinesis
  • Mitosis is division of the nucleus producing two
    genetically identical daughter cells from one
    parent cells
  • Needed for growth
  • Needed for repair
  • Cytokinesis is division of the cell contents
  • Usually they happen simultaneously

18
Phases of Mitosis
  • Prophase
  • Metaphase
  • Anaphase
  • Telophase

19
Chromosome Structure
  • Chromosome is two sister chromatids connected by
    a centromere
  • Chromosomes are made of DNA and contain genes
    (hereditary units)
  • Chromosomes are the condensed form of chromatin

20
Prophase
  • Chromatin coils into visible chromosomes
  • Nuclear membrane disintegrates
  • Nucleus disappears
  • Centrioles migrate to opposite ends of cell
  • Spindle fibers form

21
Prophase
22
Metaphase
  • Much shorter amount of time than prophase
  • Spindle fibers attach to centromere
  • Chromatids line up at the cells equator

23
Metaphase
24
Anaphase
  • Centromeres split
  • Spindle fibers shorten to pull chromatids to each
    end of cell
  • Sister chromatids separate

25
Anaphase
26
Telophase
  • Starts when chromatids get to opposite poles
  • Chromosome uncoil and become chromatin
  • Spindles breakdown
  • Nuclear membrane reforms
  • Nucleus becomes visible

27
Telophase
28
Cytokinesis
  • Division of the cytoplasm
  • Plants form a cell plate, the beginning of a cell
    wall
  • Animals have cleavage furrow where the plasma
    membrane pinches in

29
Animal and Plant Cytokinesis
30
Results of Mitosis
  • Mitosis allows for genetic continuity in each
    generation of daughter cells
  • Same chromosomes
  • Same genes
  • Same exact DNA

31
Levels of Organization
  • In unicellular organisms one organism undergoes
    mitosis to make two organisms
  • In multicellular organisms one cell undergoes
    mitosis to make two cells that form tissues
  • Tissues of different types functioning together
    form organs
  • Organs functioning together form systems
  • Systems functioning together form organisms

32
Chapter 9 Cellular Reproduction
  • 9.3 Cell Cycle Regulation

33
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34
Length of Cell Cycle
  • Each cell type has a specific growth and
    reproduction time table
  • Frog embryo cell cycle of less than one hour
  • Cells lining your intestine 24-48 hours
  • Mature nerve cells do not divide

35
Normal Control of the Cell Cycle
  • Much that science does not fully understand
  • Enzymes control the cell cycle
  • Many enzymes needed
  • Most enzymes are used at just one point in the
    cycle
  • Loss of a functional enzyme can cause the cell
    cycle to be out of control

36
Normal Control of the Cell Cycle
  • Signaling molecules made of a cyclin bound to a
    CDK kick off the cell cycle and drive it through
    mitosis.
  • Checkpoints monitor the cell cycle for errors and
    can stop the cycle if an error occurs

CDK are enzymes, cyclins are proteins
37
Genes and Proteins
  • Genes located on DNA are responsible for giving
    direction about what proteins (enzymes) to
    produce
  • A defective gene would produce a faculty enzyme
    that would not function correctly

38
Key Time for Control of the Cell Cycle
  • Key control of the cell cycle is just prior to S
    phase during interphase
  • If new DNA is synthesized then the cell will
    continue on with mitosis

39
Cancer
  • A cell out of control of the cell cycle
  • Mistake in the Cell Cycle
  • Too fast rate of mitosis
  • Result of changes in one or more genes that
    produce enzymes that are involved in controlling
    the cell cycle

40
Cancer Cells
41
Cancer Cells
  • Cancer cells form tumors
  • Tumors are masses of cells that interfere with
    normal functioning
  • Metastasis cancer cells break off the tumor and
    travel to other locations to form tumors

42
Causes of Cancer
  • Both genetic and environmental
  • When people move from one country to another
    their rate of cancer is that of the country they
    are now living
  • Example Rate of breast cancer is high in US and
    low in Japan when people move from Japan to US
    their rate of breast cancer increases

43
Environmental Causes of Cancer
Smoking
UV Light
Diet
Air Pollution
44
Environmental Causes of Cancer
Viruses Cervical Cancer
Water Pollution
45
Cancer Prevention
  • Clear link between healthy lifestyles and
    incidence of cancer
  • Low fat, high fiber diet reduces risk
  • Daily exercise reduces risk
  • No tobacco in any form reduces risk

46
Apoptosis
  • Programmed cell death
  • All animal cells have a death program
  • Fetal human tail cells have undergone apoptosis
    programmed cell death at the appropriate time
  • Plant leaves undergo apoptosis in autumn when the
    leaves are falling
  • Apoptosis can help protect organisms from
    developing cancerous growths.

47
Stem Cells
  • Stem cells are unspecialized cells that can
    develop into specialized cells under the right
    conditions

48
Embryonic Stem Cells
  • After a sperm fertilizes an egg the cell divides
    until there is 100-150 cells
  • Each of these cells can develop into a wide
    variety of specialized cells
  • Much controversy exists due to the ethical
    concerns about the source of these embryonic stem
    cells

49
Adult Stem Cells
  • Present in adults (and newborns) to produce the
    same type of cell
  • Not pluripotent (cant become any cell type)
  • In 2000 adult stem cells ere used to restore lost
    brain tissue in mice
  • Less controversy exists to the use of adult stem
    cells
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