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Cell Division and Growth
Chapter 10
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
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
Example problems
• A cube with all
sides 1 cm in length
• A cube with all
sides 2 cm in length
What happens when a cell
becomes too big?
1. The cell can die.
2. The cell can divide to produce
two new daughter cells (cell
division)
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
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
Chromosome structure
• Chromatid = each individual strand of
a chromosome
• Centromere = region where chromatids
join.
• Mitosis is a
continuous process
which can be divided
into phases.
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
Events of Interphase:
• Cell is growing in size
• Proteins,organelles, and nucleic acids
are produced
• Majority of a cell’s “life”
• Prepares for mitosis
• Chromosomes and centrioles
replicate.
Relative lifetime of a cell:
90
2.5
2.5
2.5
2.5
Interphase
Prophase
Metaphase
Anaphase
Telophase
1) Prophase
• The double
chromosomes
are visible as
threads that coil
and contract
into thick rods
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
Late Prophase:
2) Metaphase
• Centromeres line up on equator
• Two chromatids of each chromosome
become separate chromosomes
ANIMAL
PLANT
3) anaphase
• The duplicated chromosomes move to
opposite poles
• Microtubules help to move the
chromosomes.
ANIMAL
PLANT
4) Telophase
• Chromosomes uncoil and get longer
• Spindle fibers disappear
• Nuclear membrane forms around
“daughter” nuclei.
ANIMAL
PLANT
Review of mitosis
• Mitosis Movie and tutorial
Cytokinesis
• Division of the cytoplasm.
• Begins during late anaphase and
finishes during telophase in animal
cells.
Controlling cell division
• Do all cells divide at the same speed?
• Why do cells divide at different
speeds?
• When do cells divide fastest during
one’s life?
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
• 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.
Assignment
• Pages 257-259
Page 257-258 1-10,14,19,20,27,29
Page 259 1-12