Download 5.3 Regulation of the Cell Cycle

5.3 Regulation of the
Cell Cycle
Chapter 5 Cell Growth and Division
Mr. Shilala DAHS
KEY CONCEPT
Cell cycle regulation is necessary for healthy
growth.
Internal and external factors
regulate cell division.
External Factors
• External factors include physical and
chemical signals.
– Physical
• Cell to cell contact
– Chemical
• Growth factors are proteins that stimulate cell division
• Most mammal cells form a single layer in a culture
dish and stop dividing once they touch other cells.
External Factors
• Growth factors
– Broad group of Proteins
Growth Factor Examples
– Platelets – sticky
fragments of bone
marrow that help form
clots
• Contain a type of
growth factor that
helps the body repair
wounds
– Triggers the growth of
many types of cells
– Erythropoietin
• Protein
• Stimulates red blood cell
production in absence of O2
Internal factors
• External factors
trigger internal
factors, which
affect the cell
cycle
• Two of the most
important internal
factors are
kinases and
cyclins.
Internal Factors
• Kinases
– A kinase is an enzyme,
when activated, transfers
a phosphate group –
which typically increases
the energy of the target
molecule or changes its
shape
• Cells have many types of
kinases
Internal factors
– Cyclins are a group of proteins that are rapidly
made and destroyed at certain points in the
cell cycle
• Kinases in cell cycle are activated by cyclins
Apoptosis
• Apoptosis is programmed
cell death
– Normal feature of healthy
organisms balanced by cell
division
– Caused by a cell’s
production of selfdestructive enzymes
• Cells collapse inward
– Occurs in
• Development
of infants
• Plants – when leaves fall off
• Injury – necrosis
– Cell swells and bursts
webbed fingers
Cell division is uncontrolled in cancer.
• Cancer cells form disorganized clumps called
tumors.
– Benign tumors remain clustered and can be removed.
– Malignant tumors metastasize, or break away, and can
form more tumors.
normal cell
cancer cell
bloodstream
• Cancer cells do not carry out necessary
functions making tumors harmful
• Cancer cells come from normal cells
– Most cancer cells contain mutations or damage to
genes involved in cell-cycle regulation proteins
– Examples
• Oncogenes - accelerate cell cycle
• Others act as cell cycle brakes
Mutations in cell cycle
genes
• Inherited
– Breast cancer
• Exposure to
radiation or
chemicals
– Melanoma
• Carcinogens are
substances known
to promote cancer.
– Tobacco or
pollutants
• Viruses
Cancer Treatments
• Standard cancer treatments typically kill both
cancerous and healthy cells.
– Radiation and chemotherapy
– Damage cells DNA
• Most of what is known comes from lab grown
cancer cells
– HeLa Cells
– Obtained from cervical
tumor Henrietta Lacks
in 1951
• Immortal????