Honors Biology Chapter10 Section 3
SC B-2.7: Summarize how cell regulation controls &
coordinates cell growth & division & allows cells to
respond to the environment, and recognize the
consequences of uncontrolled cell division
REGULATING THE CELL
CYCLE
Essential Question
 How does cancer happen?
Cell Cultures
 Cells in a petri dish with
appropriate nutrients will continue
to grow until they come in contact
with other cells: called
 Contact Inhibition
Contact Inhibition
 similar controls in body
 occurs in wound healing
Checkpoints
 G1
 G2
 checks:
 checks:
1. do both daughter
1. did replication of
cells have intact
nuclei
2. does the cell have
what it needs for
S phase
DNA have any
major mistakes
2. is this cell ready
for M phase
Apoptosis
 if either checkpoint finds the cell
having major defects process of
programmed cell death will be
triggered
Cell Cycle & Its Regulators
Cell Cycle Regulators: Cyclins
 regulators are cell proteins
(cyclins)
 regulate timing of cell cycle in
eukaryotic cells
 dozens other proteins since
discovered
1. Internal Regulators
2. External Regulators
Internal Regulators
 proteins that respond to events
inside the cell
 allow cell cycle to proceed once
certain processes have been
completed inside cell
External Regulators
 proteins that respond to events
outside cell
 direct rate of cell division
 most important ones:
 Growth Factors
 important in embryonic development
 also used in wound healing
Tumors
 can be:
1. Benign ( ”kind”)


normal cells
will not spread/kill organism
2. Malignant ( “mal”= evil )
 cells abnormal
 will spread locally or systemically
Uncontrolled Cell Division
 Cancer
 cancer: disorder in which some of
an organisms cells have lost ability
to control growth
 Cancer cells do not respond to
signals that regulate cell division
Cancer Cells have Loss of
Contact Inhibition
Causes of Loss of Control???
 appears to have many causes:
 carcinogens
 some affect internal regulators,
some external regulators
 defect in gene p53
Carcinogens
 Nicotine
 Viruses
 Hepatitis
 Human Papilloma Virus (HPV)
 Bovine Papilloma Virus
 Tobacco Virus
 Radiation
 some Chemicals
Cancer Cells
CANCER CELLS
Skin Cells
Stomach Cells
HeLa Cells
 Henrietta Lacks died of cervical
cancer in Johns Hopkins Hospital,
Baltimore, MD in 1950’s
 Biopsies of her cervix taken to
researchers @Johns Hopkins where
they were cultured & they are still
growing!
HeLa Cells
 used in multiple medical areas:
 development of Polio Vaccine
 trip to the moon : What is the effect of
weightlessness on rate of cell
growth/division ?
 cell cloning
 gene mapping
 hybrid cell lines
HeLa Cells