Transcript Cell Cycle and Cancer

Cell Cycle and Cancer
Investigation 3
Focus Questions
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How do different tissues perform different
functions?
How does the cell cycle control cell division?
How does the loss of regulation of the cell
cycle lead to cancer?
How can cancer lead to loss of tissue
function?
Multi-cellular Organisms
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Multi-cellular organisms are made up of millions of
tiny cells.
In any one organism, there are many different types
of cells.
Cells that share a common structure and function
can be found grouped and organized into tissues.
There are four types of animal tissue: epithelial,
muscle, nerve, and connective tissue.
Multi-cellular Organisms cont.
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Two or more tissues work together to form organs.
An organ is a group of tissues that work together to
perform a specific set of functions for the organism.
There are many different organs throughout the
human body.
The lung, heart, liver, breast, and skin are just a few
of the organs throughout the human body.
The Skin
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The skin is an organ that contains several types of
tissues including connective, epithelial, nerve and
muscle tissue.
It is the largest organ in the human body!
The function of this organ is to protect the body from
external harm like the sun, heat, cold, and germs.
The skin is composed of the epidermis, dermis, and
subcutaneous layers.
The Lung
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The lung mostly contains epithelial and connective
tissues.
The function of the lung is to allow exchange of
oxygen from the air we breathe to blood so that it
can be delivered to other tissues in the body where it
is needed for normal cell function.
It also allows carbon dioxide waste in the blood that
came from tissues throughout the body to leave the
body through exhalation.
The Lung continued
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Air enters the body when we breathe through the
nose and mouth.
The air travels down the trachea (wind pipe) and into
the bronchioles.
There are bronchioles for the left and right lung lobe.
The bronchioles lead to the terminal bronchioles and
then the respiratory bronchioles that terminate in the
alveolar ducts.
The alveolar ducts are passageways that lead
directly to the pulmonary alveoli which are small air
sacs where the oxygen in the air is absorbed.
The Breast
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The breast is made of a combination of fatty,
glandular, and connective tissue.
These tissues function to supply milk for growing
infants.
Glandular tissue produces and releases substances
for use in the body.
During the majority of a woman’s life, the breast is
inactive and does not produce milk.
Milk production only occurs when the tissues
become active 3-5 days after a woman gives birth to
a child.
Tissues continued
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All of these tissues require increases in cell number
through out the life of the human body.
The skin has constant cell loss due to exposure to
UV light from the sun and various other external
insults.
The lung alveoli cells are repeatedly exposed to
damaging chemicals inhaled with the air in our
environment including pollution and cigarette smoke.
The breast must transform from inactive tissue to the
active tissue within days after a woman gives birth.
Cell Division
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The increased number of cells are supplied
though increased cell replication (or cell
division).
Cell division must be closely regulated so
that cells only divide when needed or the
organization of these of these tissues would
be destroyed making it impossible for them
to function properly.
Cell Division continued
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Cell division is also important in early childhood.
During this time of growth the human body grows at
a very fast rate.
This is due to a constant increase in the total number
of cells making up the body.
Cell Division is the process by which two identical
cells are produced from a single parent cell.
This process requires that the original (parent) cell
copies all of its contents, including DNA and
organelles, and splits these materials evenly into two
new daughter cells.
Cell Division continued
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Once an adult human is fully grown, most cells either
stop or slow down this process of dividing.
However, in certain tissues, like the skin, lung, or
active breast tissue, cell division is still needed.
Whether cell division is occurring rapidly as in a
growing child, or at a slower rate as in certain adult
tissues, this process must be carefully controlled.
Too much or too little cell division interferes with
normal tissue function.
The process that controls cell division is called the
cell cycle.
The Cell Cycle
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The cell cycle is an ordered set of events that
results in cell division—the production of two
identical cells from a single parent cell.
The cell cycle can be broken into 4 distinct phases:
G1 or GAP phase
S or DNA synthesis phase
G2 or GAP2 phase
M or Mitosis Phase
G1 Phase
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During the G1 phase, the cell produces proteins and
grows in size.
During this phase, the cell is functioning normally,
constantly making proteins.
This constant increase in proteins is what causes the
cell to get larger.
The G1 phase ends when the cell has reached a
certain size.
Then the S phase, or DNA synthesis begins.
S Phase
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During S phase, the cell will make an exact
copy of the DNA contained in the cell nucleus
through DNA replication.
At the end of the S phase, each chromosome
inside the nucleus of the cell consists of two
identical sister chromatids.
Each chromatid is made up of a double
stranded DNA molecule.
G2 or GAP 2 Phase
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During this phase, the cell has very little
activity.
The cell is no longer changing in size and is
doing minimal metabolic activity.
M Phase or Mitosis phase
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During this phase, the sister chromatids produced in the S
phase are separated and cell division (cytokinesis) occurs.
The M phase or Mitosis Phase of the cell cycle is made up of
four distinct stages:
Prophase
Metaphase
Anaphase
Telophase
When a cell is not going through one of these stages, it is said
to be in interphase.
Cancer
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If a gene that codes for the controlling protein is damaged or
mutated, then a properly functioning protein cannot be
produced.
If there is no production of the controlling proteins, the cells will
go through the cell cycle and divide unregulated.
Each new (daughter) cell will inherit the mutated gene for this
controlling protein because the cell receives an exact copy of
the DNA in the original (parent) cell.
This means that every daughter cell produced from the
originally damaged cell will also divide continuously.
Cancer continued
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Cancer is defined as a group of diseases that involve
the uncontrolled cell division of body cells.
Cancer begins when one normal body cell breaks
free from the normal controls of the cell cycle and
begins to follow its own rate of cell division.
This happens after damage to the cell’s DNA has
occurred, which affects the production of a cell cycle
controlling protein.
All cells produced by this cell, and all cells from
those daughter cells, will also follow a uncontrolled
rate of cell division.
Cancer continued
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If this process continues, a tumor, or a mass
of cells will develop.
A tumor can invade normal tissue and
therefore alter its overall organization and
structure.
This disorganization leads to an inability of
the tissue to function, which in turn means
that the organ cannot function properly.
How Cancer Spreads
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If a single cancer cell breaks away from the
tumor it can travel in the blood to other
places throughout the body.
At a new site, this single cancer cell will
proliferate and form another tumor.
This is called metastases and is how cancer
spreads.
Adenocarcinoma
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Lung cancer, called adenocarcinoma, is one of the leading
causes of death in adults.
One of the primary causes of lung cancer is cigarette smoke.
The chemicals in cigarette smoke are inhaled and absorbed by
cells in the lung.
Often when looking under a microscope at a lung tissue section
from a smoker, deposits of tar (toxins) can be seen in the cells
as small black specks.
These toxins damage DNA.
If the damage occurs on a gene that normally codes for a cell
cycle controlling protein, cancer can develop.
Adenocarcinoma continued
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However, since the damage to DNA is random, some
people can smoke for many years and not develop
cancer, while others may only smoke a few times
and even quit and still get cancer.
Even second-hand cigarette smoke (smoke inhaled
from other people smoking) can cause damage to
cells’ DNA.
Lung cancer is not only caused by smoking, but this
is thought tom be one of the leading preventable
causes of lung cancer.