10-3 Regulating the Cell
Cycle
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10-3 Regulating the Cell Cycle
Controls on Cell Division
Contact Inhibition
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10-3 Regulating the Cell Cycle
Controls on Cell Division
Controls on Cell Division
• Contact inhibition – Cells stop growing when in
contact with other cells
• Cell growth can be turned on and off by
internal and external regulators.
• Once cells reach adult stage they grow and
divide at different rates depending on cell type.
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10-3 Regulating the Cell Cycle
Cell Cycle Regulators
Cell Cycle Regulators
• Cell cycle is regulated by a specific protein
called cyclin.
• amount of protein rises and falls in time
with the cell cycle
• Cyclin directs the cell to go into mitosis.
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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 result, the second
cell enters mitosis.
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10-3 Regulating the Cell Cycle
Cell Cycle Regulators
Internal Regulators
Internal regulators - Proteins that respond to
events inside the cell
Internal regulators allow the cell cycle to proceed
only when certain processes have happened
inside the cell.
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10-3 Regulating the Cell Cycle
Cell Cycle Regulators
External Regulators
External Regulators - proteins that respond to
events outside the cell.
External regulators direct cells to speed up or slow
down the cell cycle.
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10-3 Regulating the Cell Cycle
What is the Life span of a human cell?
It depends on what cell it is. e.g. blood cell, skin cell,
stomach tissue cell
Recent studies have shown that few cells live as long
as the individual they belong to without renewal. A
majority, if not all, the cells making up the cerebral
cortex belong to this small group. The life span of
some other human cells are as follows:
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10-3 Regulating the Cell Cycle
Lifespan of select human
cells:
•
Cell Type – Lifespan
•Platelets -- 10 days
•
Granulocytes -- 10 hours to 3
days
•Skin epidermal cells -- 2 - 4 weeks
•
Stomach lining cells -- 2 days
•Red blood cells -- 4 months
•
Sperm cells -- 2-3 days
•Stomach lining cells -- 2 days
•
Stomach lining cells -- 2 days
•Macrophages -- months - years
•
Colon cells -- 3-4 days
•Endothelial cells -- months - years
•
Epithelia of small intestine -- 1
week or less
•Pancreas cells -- 1 year or more
•Lymphocytes -- 2 months - a year
•Bone Cells -- 25 - 30 years
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10-3 Regulating the Cell Cycle
Uncontrolled Cell Growth
Uncontrolled Cell Growth xxxxxxxxxxxxx
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Cancer is a disorder in which some of the body's own cells lose
the ability to control growth.
Cancer cells
• divide uncontrollably
• form masses of cells called tumors
• Tumors can damage surrounding tissues
• Metastatic cancer cell – cell that breaks loose from tumor and spreads
throughout the body
• Cancer is usually caused by a defect in gene p53
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10-3
Click to Launch:
Continue to:
- or -
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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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