Name: _______________________________________________________________Date: _________________________Block:___
Cancer
Cancer is a disease that everyone has heard about but that
few people understand.
Statistics tell us that one out of every
three Canadians will get cancer at some point in their lives.
Most cancers are found in the middle aged or older people.
However, in most of these people the cancer has been growing
for many years before they recognize it.
Normal cells do not divide unless they are given a signal by the body to start mitosis. If a cell
has been damaged or died, your body will direct nearby cells to divide to replace it.
A cancer occurs
when a cell goes “wild” and starts dividing uncontrollably to form a tumour. Cancer cells do not
follow any directions given by the body.
Cancer kills people because the tumours spread to important
body organs such as the lungs or the brain and prevent them from functioning normally.
Cancer cells look abnormal under a microscope.
They are often larger than normal cells, have
two or more nuclei, and have an abnormal number of chromosomes.
In general, all cancer cells have four features in common:
1.
All cells of the cancer originally come from 1 wild cell.
2.
The cell divides continuously and out of control of the body.
3.
The cell can separate from its neighbours, move to a new location and grow into a new tumour.
4.
The cell has an abnormal number of chromosomes.
A normal cell can become a cancer cell if the part of its DNA that controls cell division becomes
damaged.
Scientists believe that there are four different things that can change the DNA of a cell so it
becomes cancerous.
1.
Error in DNA replication.
2.
Exposure to radiation.
3.
Virus infection
4.
Chemical carcinogen (e.g. Chemicals in cigarette smoke)
Everyday a few normal cells turn into wild cells in your body.
Luckily your body has means of
recognizing these changed cells and destroying them.
All you cells have the same unique pattern of
protein molecules in their cell membrane.
These proteins are called
ANTIGENS
and like fingerprints,
every person has their own unique different antigens.
The white blood cells in your body act as
police.
But instead of checking fingerprints or ID cards, your white blood cells check the kinds of
proteins on the surface of every cell they touch as they travel around the body.
When your white blood cells discover a cell with different antigens they signal the body to produce
ANTIBODIES
. Antibodies are very specific and will only work for one type of antigen.
When
antibodies are released in your body, they act like guided missiles, ignoring all normal cells until they
attach on to the strange antigens of a bacteria or cancer cell. The antibody then sinks a hole into
strange cell’s membrane which causes the cell to explode and die.
In this way your body recognizes
and kills bacteria and cancerous cells.
Mrs. N Gill
Science 9
