Chapter 10 Cell Growth and Division

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Transcript Chapter 10 Cell Growth and Division

Chapter 10 Cell Growth
and Division
Cell Growth
A. A living thing grows because it
produces more and more cells.
1. The cells of a human adult are
no larger than the cells of a human
baby, but there are more of them.
2. The smaller the cell the better it is.
The larger the cell the more difficult to
perform cellular functions.
3. Cell division is the process whereby
the cell divides into two daughter cells.
B. Rates of cell growth
1. Cells can grow very fast.
Bacteria cell growth is calledbinary fission.
3. Bacteria will grow and grow and
then split in half into two identical
4. The amazing thing with cellular division
is how accurate it is.
Before a cell can get too large, a
growing cell divides forming two
daughter cells.
6. The process by which a cell divides into
two new daughter cells is called cell
II. Cell Division
A. The first stage of cellular division
in Eukaryotes is called mitosis.
The second stage is called
B. Chromosomes
1. In Eukaryotic cells, chromosomes
carry the genetic information that is
passed on from one generation of
cells to the next.
2. Chromosomes are made up of
DNA, which carries the cells coded
genetic information- and proteins.
The cells of every organism have a
specific number of chromosomes.
4. Example- the cells of fruit flies have 8
chromosomes and that of a human has
46 chromosomes.
Chromosomes are not visible in most
cells except during cell division.
6. Well before cell division, each
chromosome is replicated, or copied.
7. Because of this,
each chromosome
consists of two
identical, “sister”
8. Each pair of
chromatids is
attached to an are
called the
centromere. They
are like the “twist
tie” that holds the
C. The cell cycle
1. The cell cycle describes the life of
a Eukaryotic cell.
2. The cell cycle is a repeating
sequence of cellular growth and
division during the life of an
3. A cell spends 90% of its time in
the first three phases of the cycleInterphase.
4. First growth (G1)phase- a cell
grows rapidly and carries out its
routine functions. Cells that are not
dividing remain in the G1 phase.
5. Synthesis (S) phase- A cell’s DNA
is copied during this phase. At the
end of this phase, each
chromosomes consists of two
chromatids attached at the
6. Second growth (G2) phase-In the G2
phase, preparations are made for the
nucleus to divide.
7. Mitosis- The process during cell division
in which the nucleus of a cell is divided
into two nuclei.
8. Cytokinesis- the
cytoplasm splits.
D. The cell cycle is
carefully controlled.
1. If a cell spends 90% of its time in
interphase, how do cells “know”
when to divide?
2. Cell Growth (G1) checkpointThis checkpoint makes the key
decision of when the cell will divide
or not.
3. DNA synthesis (G2)
checkpoint-DNA replication is
checked at this point by DNA repair
enzymes. If this checkpoint is
passed, proteins help to trigger
4. Mitosis check point- will trigger
the exit from mitosis.
E. Mitosis
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Interphase (not really a phase)
Interphase- is part of the cell cycle
before mitosis. During Interphase
• The cell grows
• DNA is being copied
• This period between cell division can be very
Prophase- This is the longest
phase. During this phase;
• The nuclear envelope disappears.
• The centrioles start to move to the opposite
• Spindle fibers start to form.
• Chromosomes are becoming evident.
Metaphase-Metaphase is the
shortest phase of mitosis.
• The chromosomes line up in the middle of
the cell.
ANAPHASE- Begins when the
centromere that join the sister
chromatids start to split.
• The chromosomes are being pulled to the
opposite sides of the cell toward the
TELOPHASE-Final process of
• Chromosomes are at the opposite poles.
• Nuclear envelope reforms.
CYTOKINESIS-Splitting of
the cytoplasm.
Teacher note:
Teacher pick cell explorer
III. Regulating the Cell
A. Controls on cell division.
1. Scientists can observe the effects of
controlled cell growth in the lab by
placing some cells in a petri dish.
2. On the bottom of the dish is nutrient
agar, which is food for the cells.
3. Most cells will grow until they form a
thin layer covering the bottom of the
dish. (see page 250) Then the cells
stop growing.
4. If cells are removed from the center
of the dish, they will again grow until
the space is filled.
5. The same thing happens in the body
to repair from an injury.
B. Cell cycle regulators.
1. For many years scientists are
looking for something that can
regulate the cell cycle.
It was discovered that a protein
cyclin regulated the cell cycle.
3. Cyclin regulate the timing of the
cell cycle in Eukaryotic cells.
4. It was also discovered that there
are two types of regulator proteins
1- those that occur inside of the cell
and 2- those that occur outside of
the cell.
C. Internal regulators
1. Proteins that respond to events
inside the cell are called internal
2. Internal regulators that allow the
cell cycle to proceed only when
certain processes have happened
inside of the cell.
D. External regulators
1. Proteins that respond to events
outside the cell are called external
2. External regulators direct ells to speed
up or slow down the cell cycle.
Growth factors are among the most
important external regulators.
4. They stimulate the growth and division of cells.
5. Growth regulators are very important in
embryonic development and wound healing.
E. Uncontrolled cell growth.
Why is cell growth regulated so carefully?
Cancer is a consequence of uncontrolled cell
3. Cancer is a disorder in which some of the
body’s own cells lose the ability to control
4. Cancer cells do not respond to the
signals that regulate the growth of most
5. As a result, they divide uncontrollably
and form masses of cells called tumors
that can damage the surrounding tissues.
6. Cancer cells may break loose from tumors and
spread throughout the body, disrupting normal
activities and causing serious medical problems
or even death.
7. There are certain carcinogens that can cause
this to happen. Such as: tobacco, radiation
exposure, and even a viral infection.
8. Cancer is a disease of the cell cycle, and
conquering cancer will require a much
deeper understanding of the processes
that control cell division.