Cell Division and Growth

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Cell Division and Growth

• Chapter 10

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How large can a cell be? Is there a limit?

• DNA overload when a cell becomes too large
  and an information crisis occurs
• Too difficult to exchange materials
• The speed of exchange is determined by the cell
  membrane

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What determines the rate of exchange of materials?

• Surface area to volume ratio
• The larger the surface area-to-volume ratio the
  more materials a cell can exchange with its
  environment

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Example problems

• A cube with all sides 1 cm in length
• A cube with all sides 2 cm in length

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What happens when a cell becomes too big?

• The cell can die.
• The cell can divide to produce two new daughter
  cells (cell division)

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Mitosis

• Process in which a cell with a nucleus divides
  and forms two identical nuclei.
• Refers to division of nucleus
• Cytokinesis division of the cytoplasm
• Asexual Reproduction
• One parent
• Offspring identical to parent cell

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Nucleus review

• Control center
• Location of genetic material
• Chromatin material of which chromosomes are
  composed
• Histones small groups of proteins where
  chromatin is found
• Chromosome short, thick, rod-like, chromatin
  structures

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Chromosome structure

• Chromatid each individual strand of a
  chromosome
• Centromere region where chromatids join.

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• Mitosis is a continuous process which can be
  divided into phases.

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Interphase

• Not considered a phase of mitosis.
• Time when a cell is between mitotic cycles
• Often called the resting stage
• This is NOT an accurate description

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Events of Interphase

• Cell is growing in size
• Proteins,organelles, and nucleic acids are
  produced
• Majority of a cells life
• Prepares for mitosis
• Chromosomes and centrioles replicate.

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Relative lifetime of a cell
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1) Prophase

• The double chromosomes are visible as threads
  that coil and contract into thick rods

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Events of prophase

• Centrioles migrate toward opposite ends (poles)
  of the cell.
• Microtubules extend from centrioles to form
  asters and eventually a spindle.
• Toward end of prophase chromosomes begin to move
  to center (equator) of the cell
• Nuclear envelope and nucleolus disappears

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Late Prophase
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2) Metaphase

• Centromeres line up on equator
• Two chromatids of each chromosome become separate
  chromosomes

ANIMAL
PLANT
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3) anaphase

• The duplicated chromosomes move to opposite poles
• Microtubules help to move the chromosomes.

ANIMAL
PLANT
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4) Telophase

• Chromosomes uncoil and get longer
• Spindle fibers disappear
• Nuclear membrane forms around daughter nuclei.

ANIMAL
PLANT
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Review of mitosis

• Mitosis Movie and tutorial

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Cytokinesis

• Division of the cytoplasm.
• Begins during late anaphase and finishes during
  telophase in animal cells.

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Controlling cell division

• Do all cells divide at the same speed?
• Why do cells divide at different speeds?
• When do cells divide fastest during ones life?

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Regulating division

• Cyclins proteins found in eukaryotic cells that
  regulate the timing of the cell cycle.
• Internal regulators proteins that work inside
  the cell
• External regulators proteins that respond to
  events outside the cell
• growth factors, after injury, embryological

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Cancer

• Defined as uncontrolled cell division.
• If cells continue to divide over and over,
  eventually a mass of cells can be formed called a
  tumor that may interfere with normal tissuue or
  cellular functions.

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Assignment

• Pages 257-259
• Page 257-258 1-10,14,19,20,27,29
• Page 259 1-12