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Cell Growth and Division
Chapter 10
Why would we need new cells???
Growth
Repair
Cell death
Limits of cell growth
Why cells stay small…and divide

DNA Overload
Larger cells mean more demand of DNA

Exchange of material
Service area effects exchange rate

Surface area
Volume increase more than surface area
Before the cell becomes too large, it
divides into two “daughter” cells in a
process called Cell Division
Cell division
Cell Division
All cells come from
preexisting cells
Prokaryotes

Binary Fission
Eukaryotes


Mitosis
Meiosis
Cell Cycle
Series of events that
that cells go through
as they grow and
divide



Cell grows
Prepares for division
Divides into 2 daughter
cells
3 parts of the cell cycle:
Interphase
 Mitosis
 Cytokinesis

INTERPHASE- 3 phase
G1 phase





Monitor environment
and cell size
Checks for DNA
damage
increase in mass
Organelles prep for cell
division
Cell spends most of its
life in Interphase
S phase

DNA is copied
G2 phase


Intracellular
components replicated
Last chance for growth
prior to division
Mitosis


Division of the
nuclear material
4 phases
Cytokinesis

Division of the
cytoplasm
Chromosomes
Compact, coiled DNA
Sister Chromatids

One half of the
chromosome
Centromere


Between the two
chromatids
holds them together
Mitosis
How all cells divide
EXCEPT reproductive
cells
The cytoplasm and
nucleus both divide
Results in two cells
that are genetically
identical
Prophase
DNA is shortened and
tightened into chromosomes
Nucleolus & nuclear
membrane break down &
disappear
Two centrosomes appear

Spindle fibers appear
Metaphase
Spindle fibers move
chromosomes to the
center of cell
Anaphase
Chromatids separate
at the centromere and
are pulled to opposite
poles of cell by
spindle fibers
Telophase
Spindle fibers break down
Chromosome loosens up
Nuclear envelope forms
around each set of
chromosomes
Nucleolus forms
Cytokinesis
Cytokinesis-in animals
Cell membrane
pinches inward
creating a cleavage
furrow
Eventually leads to
two cells
Cell Plate
Only in
plants

Cell plate
forms
between two
nuclei
Mitosis animation
Mitosis/cell cycle Video
Mitosis /Cell cycle 3D
Regulation of the cell cycle
Not all cells divide at the same time
Cell type
Life span
Esophagus
2-3 days
can divide
Small intestine
1-2 days
can divide
Large intestine
6 days
can divide
Red blood cells
<120 days
cannot divide
White blood cells
0 hrs – decades
Smooth muscle
Long lived
can divide
Heart muscle
Long lived
cannot divide
Nerve cells
Long lived
Stomach cells
5 days
Nerve cells in brain
As old as you are
Liver
1-1.5 years
Adult skeleton
7-10 years
Outer layer of skin
2 weeks
many do not divide
most do not divide
Changes in mitosis
Aging
Cancer
mutations
AGING
Mitosis begins after fertilization and
continues until death.
All living things age.
The rate of mitosis slows down with age.
As a result of a slowing mitosis rate in
humans these things can happen: hair
loss, wrinkled skin, loss of calcium in
bones and muscle weakness,
Control of the Cell Cycle
Cyclins
Proteins that regulate the a cell’s
progression through the cell cycle
An abnormal cell should not be able to
pass checkpoint
When Control is Lost: Cancer
Cancer results if cells do not respond to control
mechanisms and start growing uncontrollably
CANCER – Cells mutate and grow, passing
checkpoints
Normally a mutant cell
is destroyed or self
destructs.

Apoptosis
This does not occur in
cancer cell
Cancer cell division
Unlike normal cells,
cancer cells continue to
divide indefinitely, even if
they become densely
packed.
Cancer cells will also
continue dividing even if
they are no longer
attached to other cells.
Metastasis
A cancer tumor grows and spreads to
other parts of body
Cancer animation
Causes of Cancer
1) carcinogen - Any substance that can induce or
promote cancer.
2) Mutagens – A substances that cause mutations.
KINDS OF CANCER
Carcinomas- tumors grow in the skin and
lining of organs. Ex. Lung and breast
cancer
Sarcomas- tumors that grow in bone and
muscle tissue.
Lymphomas- tumors that grow in the
lymph and blood. Ex. Leukemia.
Cellular Reproduction
Stem Cells- another way to produce new
cells
 Unspecialized cells
that can develop into
specialized cells
when under the right
conditions
Cellular Reproduction
Embryonic Stem Cells – unspecialized cells
 After fertilization, the resulting mass of cells
divides repeatedly until there are about
100–150 cells. These cells have not
become specialized.
Cell differentiation

the process by which a less specialized cell
becomes a more specialized cell type.
Cellular Reproduction
Adult Stem Cells
 Found in various tissues in the body and
might be used to maintain and repair the
same kind of tissue
stem cells