Transcript THE CELL CYCLE AND MITOSIS 2 Lesson 5 September 28th, 2010 CELL GROWTH AND REPAIR  Multicellular organisms are made up of many different cells. 

THE CELL CYCLE AND MITOSIS 2
Lesson 5
September 28th, 2010
CELL GROWTH AND REPAIR
 Multicellular
organisms are made up
of many different cells.
 The different types of cells undergo
growth and cell division at different
rates.
CELL GROWTH AND REPAIR
Nerve cells do not divide once they are
mature
 Intestine cells divide every 3 days.
 Cells that are likely to be damaged will be
replaced more often
 In plants, growth occurs rapidly in the meristem
region.


Cells in this region divide every 12 to 36 hours.
FACTORS THAT AFFECT MITOSIS
 Living
organisms respond to changes
in the environment
 Altitude causes more divisions of blood
cells
 Plants bend toward light because the
cells on the opposite side of the light
divide faster.
 Antibiotics called bacteriostatic drugs
can temporarily stop the replication of
DNA.
HOW LONG DO CELLS LIVE?
 The
cell cycle regulates how long a
cell lives.
 Cells die to injury or
unrepairable damage.
 Necrosis
HOW LONG DO CELLS LIVE?
A
cell that dies as a normal part of a
healthy multicellular organism is
regulated and controlled. This is called
apoptosis.
 Example: cells produced to fight
infections die when they are no longer
needed.
CANCER CELLS
A cell that divides uncontrollably is called a
cancer cell. Cancer cells develop when a change
occurs in the cell that affects how that cell
divides. When a cell’s DNA is changed, it is
known as a mutation.
 A cancer cell divides differently from a normal
cell.

CANCER CELLS

Cancer cells ignore the usual densitydependent inhibition of growth, multiplying
after contact with other cells is made, piling up
until all nutrients are exhausted. The cancer cells
proliferate to form mass of cancer cells called a
tumour. As the tumour grows larger, it begins to
release proteins from the cell to attract new blood
vessel growth (this is called angiogenesis).
CANCER CELLS VIDEO CLIP
TYPES OF TUMOURS

Benign: tumour cells remain at their
original site.
TYPES OF TUMOURS

Malignant: some tumour cells send out signals
that tell the body to produce a new blood vessel
at the tumour site. These cells not only have a
food and oxygen supply, they also have an avenue
for escape to a new part of the body - through
the new blood vessel and into bloodstream. Cells
that break away from the tumour begin to spread
to surrounding tissues (via the bloodstream or
lymph) and start new tumours = metastasis.
TYPES OF TUMOURS
UNUSUAL FEATURES OF CANCER CELLS
Cancer cells are frequently "immortal": whereas
normal cells divide about 50 times and they die,
cancer cells can go on dividing indefinitely if
supplied with nutrients.
 Cancer cells often have unusual numbers of
chromosomes or mutations in
chromosomes.

UNUSUAL FEATURES OF CANCER CELLS
Cancer cells may also have an abnormal cell
surface; instead of "sticking" to its neighbouring
cells, cancer calls tend to "round up" and break
attachments its neighbours cells, allowing for
metastasis.
 A=asymmetry
 B=borders are irregular
 C=color
 D=diameter

CARCINOGENS
Any substance or substance or energy that causes
a mutation in DNA is called a Carcinogen.
There are three types of known carcinogens
1. Viruses – Ex leukemia – cancer of the white
blood cells.
2. Radiation – UV rays, nuclear radiation.
3. Hazardous chemicals – toxic chemicals,
chemicals found in cigarettes.
 With aging free radical are produced in larger
quantities which can damage DNA and cause
mutations as well. Aging is not a carcinogen.

COMPARING NORMAL CELLS TO CANCER
CELLS
Normal Cells
- Make exact copies of themselves through
mitosis
- Reproduce for about 50-60 divisions
- Stick Together to form masses of cells as
appropriate
- Self destruct when too old or too damaged
COMPARING NORMAL CELLS TO CANCER
CELLS
Cancer Cells
-
Make exact copies of themselves through mitosis
Do not stop reproducing “Immortal”
Do Not stick together
Behave independently
May move to another location of the body.
Often have unusual numbers of chromosomes or
mutations.
COMPARING NORMAL CELLS TO CANCER
CELLS
COMPARING CANCER CELLS AND
NORMAL CELLS – DRY LAB
Complete and hand in
 This should be relatively quick which should
allow you time to work on your other labs.
