Download 1.3 The Cell Cycle in YOUR Body

1.3 The Cell
Cycle in YOUR
Body
Some common chromosome counts:
Dogs
78
Tomatoes
24
Humans
46
Black Molly (fish)
46
Cell need to divide for the following
reasons:
1.
Normal Cell Replacement
a)
Cells die of old age and need to be replaced.
See pg 25 for cell life spans.
About 3 billion cells die in your body every
minute.
a)
Cells die due to damage or when they don’t get
enough food or oxygen.
b)
Regeneration - Healing of damaged tissue or the
replacement of body parts is called regeneration.
(NOTE: see note under Figure 1.17 – pg 26)
Growth
 As organisms grow larger, their
cells stay the same size.
 They just get more of them.
Aging
 Aging is connected to the slowing of the
cell cycle.
 The cells do not divide as often or as
quickly.
Cancer
 Caused when the DNA of a cell
becomes damaged by:
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Tobacco
Asbestos
Certain chemicals
some viruses
Radioactivity
UV radiation
 The damage injures but does not kill the cell.
 The cell no longer functions properly and the
DNA no longer has correct information about
when and how quickly to divide.
 The result: Useless cells divide often and quickly
forming a lump.
 If the cancer cells can easily be transported the
cancer can spread all over.
 The lump crowds out good cells and use up a lot
of food and oxygen.
1.
Explain a process in the human body in
which there is evidence of the cell cycle
at work.
A process in the human body in which there is
evidence of the cell cycle at work would be
growth and development.
2.
Give two reasons why cells die.
Reasons why cells die include:
Damaged
Programmed to live a certain amount of time – no
longer needed
Lack of food or oxygen
Failed mitosis
3.
How do scientists currently explain
the aging process?
Scientists currently explain the aging process as
the cell cycle is slowing down.
4.
Describe what happens when cells
divide uncontrollably.
Cancer is what happens when cells divide
uncontrollably. These cells are like weeds in a
garden, choking out the healthy plants/cells.
5.
Using your knowledge about cancer
and cell division, explain how you
think sunscreen can help reduce the
risk of skin cancer.
I think sunscreen can help reduce the risk of skin
cancer because it blocks the UV rays and prevents
them from damaging the genetic material.
6.
Some cells live for years, while
others live for only a few days.
Why do you think some cells
might be replaced faster than
others?
I think some cells might be replaced faster
than others because some cells are
damaged more quickly by their
environments (stomach acid).
7.
The muscle cells of the heart were once
thought to stop dividing when a person
reached the age of nine. Thus, heart attacks,
which kill heart cells, were believed to cause
permanent damage to the heart muscle. New
research has discovered that mitosis does
occur in the heart later in life. What do you
think this new discovery means for people
who have heart attacks? (2)
This new discovery means your body is capable
of regenerating heart cells. This gives heart
attack survivors hope for recovery.