10-3 Regulating the Cell
Cycle
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10-3 Regulating the Cell Cycle
Cell Cycle Regulators
How is the cell cycle regulated?
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10-3 Regulating the Cell Cycle
Controls on Cell Division
One way to control the cell clock:EXTERNAL
REGULATION
1. Contact Inhibition
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10-3 Regulating the Cell Cycle
Controls on Cell Division
Controls on Cell Division
Experiments show that normal cells will reproduce
until they come into contact with other cells.
When cells come into contact with other cells, they
respond by not growing.
This demonstrates that controls on cell growth and
division can be turned on and off.
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10-3 Regulating the Cell Cycle
Cell Cycle Regulators
Cell Cycle Regulators
The cell cycle is regulated by a specific
protein(s).
The amount of this protein in the cell rises
and falls in time with the cell cycle.
Scientists called this protein cyclin because it
seemed to regulate the cell cycle.
Cyclins regulate the timing of the cell
cycle in eukaryotic cells.
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10-3 Regulating the Cell Cycle
Cell Cycle Regulators
Cyclins were discovered during a similar
experiment to this one.
A sample of cytoplasm
is removed from a cell
in mitosis.
The sample is injected
into a second cell in
G2 of interphase.
As a result, the
second
cell enters mitosis.
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10-3 Regulating the Cell Cycle
Cell Cycle Regulators
Internal Regulators
Proteins that respond to events inside the cell are
called internal regulators.
Internal regulators allow the cell cycle to proceed
only when certain processes have happened
inside the cell.
Ex: Can’t start mitosis unless the DNA has been
copied.
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10-3 Regulating the Cell Cycle
Cell Cycle Regulators
External Regulators
Proteins that respond to events outside the cell are
called external regulators.
External regulators direct cells to speed up or slow
down the cell cycle.
Ex: Contact inhibition
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10-3 Regulating the Cell Cycle
Uncontrolled Cell Growth
Uncontrolled Cell Growth
Cancer is a disorder in which some of the
body's own cells lose the ability to control
growth.
How are cancer cells different from other
cells?
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10-3 Regulating the Cell Cycle
Uncontrolled Cell Growth
Cancer cells do not respond to the signals
that regulate the growth of most cells.
Eg: They ignore both internal and external
signals (regulators)
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10-3 Regulating the Cell Cycle
Uncontrolled Cell Growth
Cancer cells divide uncontrollably and form masses
of cells called tumors that can damage the
surrounding tissues.
Cancer cells may break loose from tumors and
spread throughout the body, disrupting normal
activities and causing serious medical problems or
even death.
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10-3 Regulating the Cell Cycle
Environmental factors can cause changes to genes
(DNA instructions) that regulate the cycle.
1.
2.
3.
Changes to the P53 gene that is common in almost
all cancers
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10-3
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10-3
The cell cycle is believed to be controlled by
proteins called
a. spindles.
b. cyclins.
c. regulators.
d. centrosomes.
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10-3
Proteins that respond to events inside the cell
are called
a. internal regulators.
b. external regulators.
c. cyclins.
d. growth factors.
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10-3
Once a multicellular organism reaches adult
size, the cells in its body
a. stop dividing.
b. grow and divide at different rates, depending
on the type.
c. have the same life span between cell
divisions.
d. undergo cell division randomly.
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10-3
One effect of an internal regulator is that a cell
will not begin mitosis until
a. it becomes too large.
b. the cell’s growth is stimulated.
c. it is in physical contact with other cells.
d. all its chromosomes have been replicated.
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10-3
One factor common to almost all cancer cells is
a. a lack of cyclin.
b. a defect in gene p53.
c. exposure to tobacco smoke.
d. exposure to radiation.
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END OF SECTION