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Chapter 10 Notes
Cell Growth and Division
10–1
Cell Growth
pg. 241
A.Limits to Cell Growth ~ Two main
reasons why cells divide rather than grow
indefinitely is:
–
1. DNA “Overload” ~ explain
If a cell grows too large, an information crisis would occur.
The cell’s DNA would no longer be able to serve the
increasing needs of the growing cell.
–
2. Exchanging Material ~ explain
The rate at which the exchange of nutrients and waste depends
On the surface area of the cell, which is the total areas of its cell membrane.
However, the rate at which nutrients are used and waste products are
produced depends on the cell’s volume. If the cell is too large, too difficult
to make the exchanges.
Ratio of Surface Area to
Volume in Cells
Cell Size
Surface Area
(length x width x 6)
Volume
(length x width x height)
Ratio of Surface Area
to Volume
The volume increases much more rapidly than the surface area,
causing the ratio of surface area to volume to decrease. This decrease
causes serious problems for the cell. If the cell got too large, it would
be more difficult to get sufficient amounts of oxygen and nutrients in
and waste out.
Division of the Cell ~ why does
division occur & what occurs?
1. Division must occur in cells in order
for prokaryotic & one celled organisms
to reproduce and in order to develop
the various parts of eukaryotic organisms.
2.
First the cell must copy its genetic information
for each daughter cell to have a copy ~
mitosis.
Then the cell separates the contents of the cell
into two parts ~ cytokinesis.
10-2 Cell Division pg. 244
A. Chromosomes ~
Made of? Visible? Replication?
Draw diagram
1. Made of DNA ~ which carries the cell’s coded
genetic information and proteins.
2.
Chromosomes are not visible in most cells
except during cell division. Usually the chromosomes
are spread throughout the nucleus, but condense a the
beginning of cell division.
3.
Replication is to copy a chromosome. Because of this,
each chromosome consists of two sister chromatids.
As the cell divides, the sister chromatids separate from
each other and one chromatid goes to each of the new cells.
Chromosome
Diagrams
c. Cell Cycle ~
definition, phases
are… & what happens in each?
1. During the cell cycle, the cell grows, prepares
for division & divides to form two daughter cells.
2. G1 phase – cells increase in size and synthesize
new proteins & organelles.
3. S phase – chromosomes are replicated and the
synthesis of DNA molecules takes place.
4. G2 phase – the shortest phase; many of the
organelles & molecules required for cell division
are produced.
5. M phase – mitosis (cell division)
Figure 10–4 The Cell Cycle
G1 phase
M phase
S phase
G2 phase
• The cell cycle represents recurring events
that take place in the period of time from
the beginning of one cell division to the
beginning of the next. In addition to cell
division, the cell cycle includes periods
when the cell is growing and actively
producing materials it needs for the next
division.
1. Why is the cell cycle called a cycle?
It represents recurring events.
2. Why do you think that it is important for a cell to grow in size during its cell
cycle?
If a cell did not grow in size,
each cell division would produce progressively smaller cells.
3. What might happen to a cell if all events leading up to cell division took place as
they should, but the cell did not divide?
Some might infer that a cell that undergoes all sequences of the
cell cycle would grow increasingly larger—to a point at which the cell
could no longer exchange materials with the environment efficiently enough to live.
E. Mitosis
pg. 246
~
are…& what happens?
1.
2.
four phases
Prophase ~ the first and longest phase when the
chromosomes become visible. Centrioles take up positions
on opposite sides of the nucleus. The spindle fibers attach to
centromere, the nucleolus disappears, and the nuclear
envelope breaks down.
Metaphase ~ often lasts only a few minutes. The chromosomes
line up across the center of the cell. Microtubules connect the
centromere to the poles of the spindle fibers.
3.
Anaphase ~ The centromeres of the sister chromatids split
and the chromatids separate to become individual
chromosomes. The chromosomes move untill they separate
into two groups near the poles of the spindle.
4.
Telophase ~ The chromosomes begin to disperse into a
tangle of dense material. The nuclear envelope reforms.
Animal Cell Mitosis
F. Cytokinesis
& what happens?
1.
pg. 248
~
definition
Cytokinesis is the division of the cytoplasm
& usually occurs at the same time as telophase.
animal cells, the cell membrane is drawn
2. Ininward
until the cytoplasm is pinched into two
nearly equal parts.
3.
In plant cells, a cell plate forms midway between the
divided nuclei and gradually develops into a
separating membrane. A cell wall then begins to
appear.
cytokinesis
Figure 10–5 Mitosis & Cytokinesis
Spindle
forming
Centrioles
Nuclear
envelope
Chromatin
Interphase
Centromere
Chromosomes
(paired chromatids)
Prophase
Cytokinesis
Spindle
Centriole
Telophase
Nuclear
envelope
reforming
Centriole
Individual
chromosomes
Anaphase
Metaphase
Figure 10–5 Mitosis & Cytokinesis
Spindle
forming
Centrioles
Nuclear
envelope
Chromatin
Interphase
Centromere
Chromosomes
(paired chromatids)
Prophase
Cytokinesis
Spindle
Centriole
Telophase
Nuclear
envelope
reforming
Centriole
Individual
chromosomes
Anaphase
Metaphase
Figure 10–5 Mitosis & Cytokinesis
Spindle
forming
Centrioles
Nuclear
envelope
Chromatin
Interphase
Centromere
Chromosomes
(paired chromatids)
Prophase
Cytokinesis
Spindle
Centriole
Telophase
Nuclear
envelope
reforming
Centriole
Individual
chromosomes
Anaphase
Metaphase
Figure 10–5 Mitosis & Cytokinesis
Spindle
forming
Centrioles
Nuclear
envelope
Chromatin
Interphase
Centromere
Chromosomes
(paired chromatids)
Prophase
Cytokinesis
Spindle
Centriole
Telophase
Nuclear
envelope
reforming
Centriole
Individual
chromosomes
Anaphase
Metaphase
Figure 10–5 Mitosis & Cytokinesis
Spindle
forming
Centrioles
Nuclear
envelope
Chromatin
Interphase
Centromere
Chromosomes
(paired chromatids)
Prophase
Cytokinesis
Spindle
Centriole
Telophase
Nuclear
envelope
reforming
Centriole
Individual
chromosomes
Anaphase
Metaphase
Figure 10–5 Mitosis & Cytokinesis
Spindle
forming
Centrioles
Nuclear
envelope
Chromatin
Interphase
Centromere
Chromosomes
(paired chromatids)
Prophase
Cytokinesis
Spindle
Centriole
Telophase
Nuclear
envelope
reforming
Centriole
Individual
chromosomes
Anaphase
Metaphase
Concept Map
Cell Cycle
includes
G1 phase
Interphase
M phase
(Mitosis)
is divided into
is divided into
S phase
G2 phase
Prophase
Metaphase
Anaphase
Telophase
• Suppose you had a paper cut on your
finger. Although the cut may have bled
and stung a little, after a few days, it will
have disappeared, and your finger would
be as good as new.
1. How do you think the body repairs an injury, such as a cut on a
finger?
The cut is repaired by the production of new cells through cell division.
2. How long do you think this repair process continues?
Cell division continues until the cut is repaired.
3. What do you think causes the cells to stop the repair process?
When the cut is filled in, there is no room for more cells to grow.
10–3 Regulating the Cell Cycle
pg. 250
A. Controls on Cell Division ~
what controls & how tested?
1. Contact of other cells stops growth.
2. Cells were place in a petri dish to
find that when the cells contact
other cells, the growth stops.
Control of Cell Division
B. Cell Cycle Regulators ~
what regulates, who discovered?
1.
2.
Cyclin, a protein, regulates the
timing of the cell cycle in
eukaryotic cells.
Tim Hunt of Great Britain & Mark
Kirschner of the US performed
experiments with cells in
mitosis.
Figure 10–8 Effect of Cyclins
The sample is
injected into a
second cell in G2
of interphase.
A sample of
cytoplasm is
removed
from a cell in
mitosis.
As a result, the
second cell
enters mitosis.
a. Internal Regulators ~
definition &
examples
~Proteins that respond to events inside the cell are called internal
regulators.
~Several internal regulators make sure that a cell does not enter
mitosis until all its chromosomes have been replicated.
~Another regulatory protein prevents cells from entering anaphase
until all the chromosomes are attached to the mitotic spindle.
b. External Regulators ~ definition &
examples
~Proteins that respond to events outside the cell are called
external regulators. They direct cells to speed up or slow
down the cell cycle. Growth factors are the most
important.
~Embryonic development & wound healing are examples.
Uncontrolled Cell Growth
pg. 252 Reasons for growth, causes of
loss of growth control, defective gene
1. The loss of growth regulators is the
reasons for uncontrolled growth.
2. Various forms of cancer causes including:
3.
Smoking tobacco, radiation exposure and
viral infections.
The Gene called p53 is found to be defective in
numerous cancer cells. Normally the gene halts the cell
cycle until all chromosomes have been replicated.
Damaged p53 genes cause cells to NOT respond to
signals that would control cell growth.
D. Stem Cells: Promises & Problems
pg. 253
1. Stem Cells in Medicine
Stem cells may allow the body to produce
replacement cells that have been damaged
due to injury or disease.
2. Sources of Stem Cells
Human embryonic tissue
3. Your Opinion on Stem Cell
Research