Download File

Fun Fact!
• There are over 200 different types of cells in the human
body, each performing specific functions!
– Nerve cells, eye cells, cardiac cells, etc.
Do all types of cells go through the cell cycle at the
same rate?
NO!
Some cells divide quickly & some divide slowly. Some types
of cells do not undergo cell division at all!
Different cell types divide at different rates!
• Muscle & nerve cells do not divide once they have
developed.
– Has anyone ever told you that once you kill your brain cells,
you don’t get them back?
• Skin cells & cells in the bone marrow divide rapidly.
Regulating
the Cell Cycle
Control of Cell Division
• Cell growth & cell division can be turned on & off.
When you’re injured, your cells
divide rapidly to repair the
injury.
When the injury has healed, the
cells stop dividing.
Regulation of the Cell Cycle
• Controlling the cell cycle is necessary for healthy growth.
• Internal & external factors regulate cell division.
– External factors include physical & chemical signals.
– Internal factors include proteins that control cell division.
For example…
• Apoptosis is programmed cell death, or “cell suicide”.
– A normal feature of healthy organisms
– Caused by a cell’s production of self-destructive enzymes
Webbing of the fingers &
toes is normal in developing
infants.
Before the baby is born,
apoptosis occurs & enzymes
destroy the extra tissues
between the fingers.
Uncontrolled Cell Growth
What happens when your cells lose control & cannot
regulate their cell cycle?
• When cells in your body cannot control cell growth &
division, cancer may form.
• Cancer cells cannot respond to the signals that regulate
the division of cells.
Uncontrolled Cell Growth
• When cancer cells have been
dividing uncontrollably, tumors
form.
• Tumors can damage
surrounding tissue.
• Cells from tumors can break
free & travel to other parts of
the body, forming new tumors.
Uncontrolled Cell Growth
Most mammal cells form a
single layer in a culture dish &
stop dividing once they touch
other cells.
Cancer cells do not carry out
necessary functions.
They come from normal cells
with damage to genes involved
in cell cycle regulation.
Carcinogens
• Substances known to promote
cancer
• Some reasons that cells may lose
the ability to control growth:
– Smoking
– Radiation Exposure
– Viral Infection
• Scientists who study cancer
research how cells divide.
Treatment
• There are several methods of treating cancer.
• Standard cancer treatments typically kill both
cancerous cells & healthy cells.
– This is why there are so many side effects.